| Moderated by: Greg Fletcher | ||
| Author | Post | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
stevegarnjobst Member 
|
I recently purchased Jensen Healey #19064, a yellow 1974 JH5, with the intent to campaign the car in the SCCA's F Street Prepared autocross class. The SCCA is re-classing the J-H for the 2016 season, moving it from a class where it's been totally uncompetitive for many years, into a class where it should be a good match for the top vehicles. SCCA's Street Prepared (SP) allows extensive suspension and wheel/tire options, but permits only limited bolt-on engine upgrades, and most interior and bodywork parts must stay intact. SP rules do include a provision for update/backdate across model years, so parts from the entire production run of the J-H may be utilized. This allowance will be particularly useful in removing excess weight from the car, as I already have a set of lighter Series 1 bumpers sitting in the garage, waiting to replace the ridiculously heavy Series 2 bumpers now on my car. Based on the unique aspects of the SP rules, I'm planning an upgrade path that should be a bit outside the norm for J-H's. I plan to document the build, and share any unique parts developed with the J-H owner community. -Steve Attachment: 00B0B_2lY1Ky9t1nh_600x450.jpg (Downloaded 318 times) |
|||||||||
|
stevegarnjobst Member
|
So a bit more about the car I'm starting with. It's a very mechanically sound vehicle that received what appears to be a relatively competent amateur body-off restoration about 8 years ago. It isn't a show car, but appears rust-free and relatively free of issues at this point. The car appears almost totally stock, with the exception of some Spax shocks and a replacement fuel pump. Note: the engine was replaced with an identical unit from another low-mileage J-H that was parted out, due to bodywork issues. Although SP permits some modifications that permanently change the vehicle (fender cutouts/flares in particular), my goal for this build is to only make modifications that are easily reversible. |
|||||||||
|
stevegarnjobst Member
|
Preliminary list of planned modifications: Basic retrofit/removal retrofit Series 1 bumpers remove vapor control system remove spare tire & bracket remove stereo system replace stock battery w/lightweight AGM battery (8 lbs) Cockpit upgrades replace stock steering wheel with Mountney leather wheel replace stock seats with Kirkey Pro Street Drag race seats replace stock belts with 3" lap belts engine/drivetrain upgrades Replace Strombergs w/EFI system (currently planning to use the LotusBits kit, featuring Jenvey throttle bodies) Electronic ignition Replace stock exhaust system with lightweight single pipe system, probably custom-fabricated Header - could use input on this. Is the available 4-1 header measurably superior to the stock 4-2-1 unit? I have a perfectly serviceable 4-2-1 unit on the car now. Is it worth replacing? Replace engine-driven fan with electric fan limited slip differential (more to come on this after my visit to the UK later this month) Note: no cam or other internal engine upgrades allowed in SP Suspension upgrades Upgraded springs (currently thinking 550 front, 250 rear) Custom Speedway Engineering blade-adjustable swaybars QA1 double-adjustable aluminum shocks rear suspension conversion to 3-link with Watts link. Lots of thought going into this one. The end result could be a set of bolt-in upgrades that dramatically improves the J-H rear suspension. Still working through the details, though. brake upgrades lightweight disc brakes front and rear (HiSpec Motorsport) wheel/tire upgrades 255/40-13 Hoosier A7's on 13" x 10" wheels That's the basic plan. I look forward to sharing my progress throughout the Winter, and am sure I'll be asking for guidance as I deal with the challenges of upgrading a 40 year old British car. Last edited on 11-07-2015 01:26 am by stevegarnjobst |
|||||||||
|
Tim Murphy Member 
|
Duplicate post. Last edited on 11-07-2015 07:33 am by Tim Murphy |
|||||||||
|
Tim Murphy Member
|
Can you remove the convertible top and the frame? The frame is steel and very heavy. I think the gas tank needs to be addressed. Changing to EFI seems like a long, involved project. Maybe do that later. I would run it close to stock and schedule your mods and upgrades based on those runs. Try to keep your car street and track ready as you do your upgrades. A common mistake made by inexperienced amateurs like me is taking everything apart then never getting it all together again. Last edited on 11-07-2015 07:37 am by Tim Murphy |
|||||||||
|
stevegarnjobst Member
|
Tim Murphy wrote:Can you remove the convertible top and the frame? The frame is steel and very heavy. I think the gas tank needs to be addressed. Changing to EFI seems like a long, involved project. Maybe do that later. I would run it close to stock and schedule your mods and upgrades based on those runs. Try to keep your car street and track ready as you do your upgrades. A common mistake made by inexperienced amateurs like me is taking everything apart then never getting it all together again. Tim, Building a car to limited prep race rules like those in SCCA Street Prepared can sometimes be an odd process. Often the allowances seem to offer very wide latitude in some areas, but very little flexibility in others. For instance, while the rules offer a great deal of flexibility to re-engineer a fixed axle rear suspension, I must retain the stock soft top and stock fuel tank. In the case of the soft top, the only way I could remove it would be if Jensen at some point provided written documentation indicating the soft top could be removed from the car as an option for normal use. If anyone has a copy of any such directive from Jensen, PLEASE send it my way! For the fuel tank, the only way I could replace it is by meeting more restrictive safety rules, which would mean adding a roll bar for an open vehicle. That would add more weight than I can remove with a fuel cell, so the stock tank stays. The EFI may not happen for the car's first season - it all depends on how smoothly the suspension upgrades go. The Watts link, in particular, may be a little tricky, as I have limited space for the mounting brackets, and will have to re-route the exhaust and a few other minor items. As for keeping the car drivable, this isn't my first build of this type, so I'm pretty used to a phased upgrade process. This particular build is also relatively mild, compared to some of my past vehicles, as it will remain street legal and fully capable of being driven to local events. For reference, I have attached a photo of my old Miata race car. Definitely NOT street legal, it weighed 1,760 lbs and made over 300whp. Fun car, but expensive to keep running. -Steve  |
|||||||||
|
stevegarnjobst Member
|
Note - I typically keep pretty close tabs on weight reduction efforts. I have a set of corner-weight scales sitting in my garage, so I can easily verify the impact of any change. The baseline starting weight for the car is 2,432 lbs, which includes a full tank of fuel and the spare tire. I have a long way to go, in order to reach my target weight of 2,100 lbs. First reductions: remove spare tire & bracket -35.2 lbs lightweight battery -26.7 lbs Last edited on 11-07-2015 09:48 am by stevegarnjobst |
|||||||||
|
Tim Murphy Member
|
Steve, thanks for the reply. You obviously have a lot of experience building race cars and I none. I was just sharing thoughts that came to mind when I read your post. I am glad to see a JH being modified and improved by someone with experience. Thanks for your plan on documenting and sharing your build. |
|||||||||
|
stevegarnjobst Member
|
Tim Murphy wrote:Steve, thanks for the reply. You obviously have a lot of experience building race cars and I none. I was just sharing thoughts that came to mind when I read your post. I am glad to see a JH being modified and improved by someone with experience. Thanks for your plan on documenting and sharing your build. I welcome all suggestions & comments. While I've been wrenching on cars for a while, the J-H is a new experience for me. While the cars generally seem pretty simple & straightforward, I'm already discovering a few of those wonderful idiosyncrasies British car designers seem particularly adept at. For example, I spent over an hour yesterday replacing a fuel tank vent line - a task that should have take a few minutes, save for the idiotic location of the fitting on the fuel tank. |
|||||||||
|
Tim Murphy Member
|
I don't know the rules, but those large, molded, rubber front floor mats are heavy. Replacing those with some carpet mats purchased at an auto parts store will save around 10, 15 pounds by my guess. |
|||||||||
|
stevegarnjobst Member
|
Tim Murphy wrote:I don't know the rules, but those large, molded, rubber front floor mats are heavy. Replacing those with some carpet mats purchased at an auto parts store will save around 10, 15 pounds by my guess. Interesting you should mention those mats. I was staring at them today, thinking about how heavy they probably are. It's allowable to remove the mats - in fact, they are typically supposed to come out if not securely fastened. I probably need to put something down on the floor to provide a bit of traction, but that will be a lot lighter than the mats. In my Miata, I coated the floors with truck bed liner paint, which provides a very durable, high traction surface. Not 100% sure I want to use that stuff on the J-H, as it's pretty difficult to remove later, but you have me thinking... Last edited on 11-09-2015 03:47 am by stevegarnjobst |
|||||||||
|
Tim Murphy Member
|
The mats are heavy. If you went with truck bed liner paint I don't think you would have to remove it later, JH floors are notorious for rusting, water leaks in thur the air vent in front of the windshield when the car is washed or caught in the rain. So most floors have had some anti rust treatment and look bad. Just cover with carpet or mats for everyday use if necessary. In the interest of safety I want to point out Ron Earl's post about a failure of his drive shaft or U joints while racing: http://www.jensenhealey.com/forums/view_topic.php?id=786&forum_id=10&page=1 |
|||||||||
|
subwoofer Member
|
Would you be allowed to replace the bumpers with the early type? Should save a quite few tens of pounds right there, the rubber bumpers are heavy. I can't remember where I heard it, but the pair weighs in at around 110 pounds? Changing over to EFI shouldn't be too much work, especially with Mike's pieces. But expect a trip to a (steady state) dyno to make the most of it. Are you allowed to increase the compression ratio? The JH desperately needs at least one more point of compression, preferably two or more. -- Joachim |
|||||||||
|
stevegarnjobst Member
|
subwoofer wrote:Would you be allowed to replace the bumpers with the early type? Should save a quite few tens of pounds right there, the rubber bumpers are heavy. I can't remember where I heard it, but the pair weighs in at around 110 pounds? I already have a set of Mark 1 bumpers sitting in the garage, waiting for a trip to the powdercoat shop. The set only weighs 29.4 lbs, including the brackets. I haven't pulled the rubber bumpers off yet, but don't doubt the 110lb figure, as those things are HUGE. Unfortunately, high compression pistons and/or cam upgrades aren't allowed. So power upgrades will be limited. Going with EFI should at least help keep the power more consistent and predictable. I have a very meticulous tuner I've worked with for years who can optimize the tune for me. I assume this will take a bit of work, as Mike's base maps likely assume some of the upgrades I'm not allowed. Last edited on 11-09-2015 12:20 pm by stevegarnjobst |
|||||||||
|
stevegarnjobst Member
|
Tim Murphy wrote:In the interest of safety I want to point out Ron Earl's post about a failure of his drive shaft or U joints while racing: http://www.jensenhealey.com/forums/view_topic.php?id=786&forum_id=10&page=1 That's scary. Drivetrain safety measures, such as SFI bellhousings, tranny blankets & driveshaft hoops aren't required for my prep level, but installing a hoop may be a good minimum safety measure. |
|||||||||
|
subwoofer Member
|
stevegarnjobst wrote:Unfortunately, high compression pistons and/or cam upgrades aren't allowed. So power upgrades will be limited. Going with EFI should at least help keep the power more consistent and predictable. I have a very meticulous tuner I've worked with for years who can optimize the tune for me. I assume this will take a bit of work, as Mike's base maps likely assume some of the upgrades I'm not allowed. Are you allowed to touch the head? Just cleaning up the bowls of the ports and radius grinding the seats should make the head flow better, and pulling the cams together a bit will add overlap and move the torque a bit upwards in RPM, if you balance it so it will take the extra RPM. But: personally I would never go racing in a car without even a roll bar, a 6-point cage is really the minimum. Are you serious that you can race with the stock windscreen and nothing else? -- Joachim Last edited on 11-09-2015 01:30 pm by subwoofer |
|||||||||
|
stevegarnjobst Member
|
subwoofer wrote:Are you allowed to touch the head? Just cleaning up the bowls of the ports and radius grinding the seats should make the head flow better, and pulling the cams together a bit will add overlap and move the torque a bit upwards in RPM, if you balance it so it will take the extra RPM. No head porting allowed. I can do intake & exhaust port matching up to 1" deep, which is apparently of some help on these engines. I'm hoping to make it through the first season without tearing the engine down, as I have plenty of suspension sorting to accomplish before more power will become a priority. Since I'm not allowed to change the stock valve springs or connecting rods, I was assuming a higher rev limit wouldn't be advisable. However, if I can safely get a few hundred extra revs with a balanced, but otherwise internally stock 907, that could be useful. Even if the power is falling off, avoiding extra shifts can be valuable in autocross. No roll bar required for the low speed autocross events the car will primarily be used for. It's also a street-legal vehicle, so I would be concerned about street safety with a roll bar, as they're typically not safe to use without a helmet - especially in a smaller vehicle, where your head is so close to the bars. If I ever choose to use the car for higher speed track events, it will receive appropriate safety upgrades (roll bar, full safety harness, extinguiser, etc). -Steve Last edited on 11-09-2015 01:50 pm by stevegarnjobst |
|||||||||
|
Esprit2 Member
|
Steve, The very early 907 Mk I intake ports were 24.5 mm tall. Later, they were increased to 25.5 mm as a running change. At the time of the change, the production of the small port head ended and the large port head became the official standard service replacement. Sorry, but no, I don't know the date or engine number of the port change, but I do believe it was within the life span of the Jensen-Healey's 907 Mk II engine. If the Update-Backdate rule would apply to that, and if your engine's ports are the small ones (minority of all 907s built), then you could have a small but real increase in port size available. The 907 responds very well to intake improvements, and the 1mm larger ports along with just port matching could pay noticeable dividends. The J-H 907's stock C-cams were designed to run at 110 MOP, both intake and exhaust. The first test engines met then-current emissions standards, but Lotus was looking down the road at the already announced 1974 standards. The engine met those coming requirements as well, but by such a narrow margin that Lotus wasn't comfortable in terms of warranty costs relative to the engine staying in compliance with age and wear. The cam timing was changed to 115 MOP for both intake & exhaust so the first production engines could pass the coming 1974 standards by a wider margin. However, that lowered the power by 10 Hp, and the engine became lethargic by comparison to the original 110 timing. Later J-H engines did go to 110/110 from engine #4030, and North American engines went to 100 IN/110 EX from engine 10480. That last config, along with really lame ignition timing and lean mixture, was the weakest of the lot and lead to the "torqueless wonder" nick name. Both 110 & 115 MOP are on the same pulleys, whether both values are marked or not. No new parts are required, it's just a matter of how the pulleys are installed. Flip the pulleys over and rotate them a few teeth, and there's the other MOP. Would that violate the rules for your class? Set both stock cams to 110 MOP, set the static ignition timing to 12 BTDC, BALANCE the carbs, set the idle mixture for peak manifold vacuum at slow idle, and use the 25.5 mm intake ports with a port-matched manifold. That won't unleash a monster, but the engine will at least run like it's interested. The original tappets were chilled cast iron, and 'old' ones are prone to cracking. I often find cracks the full height of the skirt, and I've had two crack in half in my hands during inspection. A tappet failure is as effective as a broken timing belt at wiping out valves. If you're going to use the engine in competition, bouncing off the rev-limiter, then I strongly recommend that you install a set of the later steel tappets. When the steel tappets were introduced, Lotus discontinued manufacture of the cast tappets, and the steel ones became the standard service replacement. So, going steel shouldn't be a breach of the rules since you're using factory spec parts. Cast tappets were the #1 limiter in setting the 907's rev limit. Rods were #2, but at a higher rpm. Lotus steel tappets are expensive. Both JAE in California and Garry Kemp in the UK sell aftermarket steel tappets that are less expensive while arguably being better. Their tappets also come with optional crown thicknesses that can be used to compensate for re-ground cams, or to move the range of 'required' valve shims further up into the 'available' range. Valve recession and/or grinding the valves forces the use of thinner and thinner shims. When you get to the bottom of the range of available shims, thinner tappet crowns can move the required shim thickness back up higher into the available range. Factory balance specs were: Rods to within 2 grams Crank to within 15 grams Pistons to within 3.5 grams. Doing better than that is pretty easy, and still meets the 'within' wording. Shot-peen the stock rods, balance, balance, balance everything from piston crowns to clutch, and you could be running at 8000 rpm with otherwise stock parts. Regards, Tim Engel |
|||||||||
|
Esprit2 Member
|
The current composite cylinder head gasket's crushed thickness is 0.020" thicker than the old steel-asbestos-steel gasket's. That lifts the head 0.020" higher off the block deck, lowering the compression ratio by about half a point. 8.4:1 becomes 7.9:1. The maximum cut on the bottom of the cylinder head for truing the surface is 0.020". I'm just sayin'. From the introduction of the new gasket onward, Lotus decked the block 0.020" lower and seated the liners another 0.020" deeper into the block to maintain the correct 'nip' (the liner's exposure above the block deck). For most owners of an older engine, that's not a very practical option. If you ever rebuild the engine, including replacing the original pistons, specify a half-point higher compression than you're really targeting. All 907s were built with the original low-spec head studs, and they're known to stretch with sustained full throttle running (track days, motorsports, etc). Stretch leads to blown head gaskets. The 'new' composite gasket requires the use of Lotus' later upgrade head studs (identifiable by a depressed dimple in the upper end), along with a revised, higher torque spec. The gasket's higher torque spec 'will' over-stretch the original 907 studs. "IF" you don't replace the low-spec head studs, then stay with the original 'Lotus' torque spec out of consideration for the studs. You won't be getting the full advantage of the composite gasket, but you won't be over-stretching the studs either. Note that the J-H head torque spec was too high, crushed the old gasket, and caused problems with blown gaskets. Lotus reduced the torque spec to a level that didn't crush the gasket, or over-stretch the studs. If you're going to stay old-school, it would be better to follow the Lotus torque spec instead of the one in the J-H Workshop Manual. Lotus Cylinder Head Torque Spec: (Tighten Cold, Oiled Threads & Washers) 70 Lbs-ft - Front & Rear Pairs 75 Lbs-ft - Three Middle Pairs Work up to it in several smaller steps, working from the center outward in a criss-cross pattern. Regards, Tim Engel Last edited on 11-18-2015 06:25 pm by Esprit2 |
|||||||||
|
stevegarnjobst Member
|
Tim, This is VERY helpful information! My J-H is a later '74 JH5, so I'm assuming it came with the larger port head. However, the engine was replaced, so I'm not 100% sure the current engine is identical to the original. I'll definitely need to verify everything. Were all the stock tappets cast iron? If so, I'll likely need to replace them, as the engine is reportedly an un-rebuilt unit with 30K miles. The timing changes are allowed. In fact, I can even add adjustable cam pulleys. I noticed Lotusbits has some vernier units on the shelf - might they be worth having? By the way, do you have any recommendations for head/balance work? I've had good luck with Headwerks in the past, but I have no idea if they have experience with these engines. Is there anyone semi-local you recommend for 907 work? -Steve Esprit2 wrote: Steve, |
|||||||||
|
Esprit2 Member
|
Steve, I just edited Post #19 to add a cylinder head torque spec. If it wasn't there when you read it, go read it again. Regards, Tim Engel |
|||||||||
|
stevegarnjobst Member
|
Thanks. Note - I just heard back from Mike @ Lotusbits. No vernier pullies for the older square tooth belts, but he has a conversion to the newer belts. Not sure that conversion is allowable under the SCCA rules. If it were, is the update worthwhile? |
|||||||||
|
Esprit2 Member
|
stevegarnjobst wrote:Were all the stock tappets cast iron?ALL 907s were originally built with chilled cast iron tappets. When Lotus made the change to steel for the mid-late eighties (?) 910, the spec applied retro-actively to all 9XX engines as Service Replacement parts. stevegarnjobst wrote: The timing changes are allowed. In fact, I can even add adjustable cam pulleys. I noticed Lotusbits has some vernier units on the shelf - might they be worth having?The adjustable pulleys are a pain to install, since you then have to degree the cams. It's a lot of putzy work, but doable. Given the rules restrictions on mods you can make to the engine (basically none), I don't think the gains on a milquetoast 'stock' engine due to degreeing the cams is worth the effort. Hotrod it, then yes, degree the cams. On the other hand, whenever the distance between the cam centerlines and the crank centerline changes (composite gasket's crushed thickness or milling the head or block deck), the cam timing changes. Cut the head, and there's that much extra slack goes into the timing belt. By definition, the cam timing is spec'd at TDC, so the crank can't be allowed to move. So when the tensioner pulls the extra slack out of the long run from the crank to the exhaust cam pulley, the slack must go up over the pulleys, rotating them slightly counter-clockwise, retarding the cam timing. Similar-but-different, the composite head gasket's thicker crushed thickness raises the head, and advances the cam timing. In those cases, the only recourse is to accept the timing change, or install adjustable cam pulleys. stevegarnjobst wrote: By the way, do you have any recommendations for head/balance work? I've had good luck with Headwerks in the past, but I have no idea if they have experience with these engines. Is there anyone semi-local you recommend for 907 work?I've not used anyone local for really "porting" the head. But since you can't do that by rule, I have had Aaron's Machine in Scandia port-match several Lotus 9XX engines for LOON members (local Lotus club). He's good, has a reasonable shop rate ($/hr), and has been the LOON's default 9XX machine shop for many years. He's not a 907 expert, but he has done machine work on more of them than any other shop I know of in the Twin Cities. Aaron is a general automotive machinist (everything except crank grinding) and race engine builder (snowmobiles to outboards to dragsters). He has the fastest boat on the St Croix River, with twin blown big-block V8 race motors in the back (basically AA-Fuel dragster motors). Aaron's Precision Machine (Lotus Experience) 24014 Olinda Trail N, Scandia, MN 55073-9641 (651) 443-4219 Having said that, I've also been happy with work done by Total Engine in Bloomington, JAX in Hamil (sp?), and Engelke Machine in Lester Prairie. And Cylinder Head Services in Minneapolis (near Top Gear Autoworks) has rebuilt one J-H 907 head that I know of. That was just a straight, by-the-book rebuild. The guy I used to use for Lotus heads has retired... :-( In the USA, I think West Coast Racing Cylinder Heads in California has the most experience porting 9XX heads. In the UK, Mike Taylor at Lotusbits does a great job of porting Lotus heads. There's a picture of his "Ported" 9XX head on the Lotusbits website, but ask to see his "Well Ported" head. It has huge ports. So big that the intake manifold can't be port matched to it without the wall thickness getting too thin. So he makes a full billet manifold that 'looks' factory, but with bigger runners. Ask him about ported heads during your visit to Lotusbits. I have all my crankshaft work done by: Engelke Machine 17734 County Road 9, Lester Prairie, MN 55354 (320) 395-2982 oengelke@hutchtel.net They've done a bunch of Lotus cranks. Crankshaft Supply in Minneapolis can do all crank work as well, and they're closer, but you pay big-city rates for it. Small-town Engelke Machine does quality work at a fraction of the cost. Other Engelke family businesses (brother/ uncle ??) in LP are: Lester Prairie Engine (racing engines, primarily circle track & tractor pulling). Berry Cam Service (regrind, restore, custom). 1948 175th St / PO Box 697, Lester Prairie, MN 55354 (320) 395-2377 Aaron, Engelke, Total, and JAX have all done balancing for me, and did good work. As far as balancing specialists are concerned, I've not used either of the following, I'm just aware of them. Is / was ?? I can't say if either one is still in business. Minneapolis Electronic Balancing Co (612) 781-2755 3620 Central Ave NE, Minneapolis, MN 55418 I talked with him about balancing a Lotus engine, once. He was less than enthusiastic about the job, so I moved on. Superior Balancing 23245 Agate Lake Rd, Deerwood, MN 56444 (218) 546-8417 Regards, Tim Engel Last edited on 11-18-2015 06:33 pm by Esprit2 |
|||||||||
|
Esprit2 Member
|
stevegarnjobst wrote:Not sure that conversion is allowable under the SCCA rules. If it were, is the update worthwhile?Yes. The round-tooth HTD timing belt has much deeper tooth engagement, and is far less likely to jump timing. On an interference engine, that's great mechanical insurance to have. Also, all trapezoidal timing belts are made with 1960's technology. No new engines have been manufactured using that belt since the introduction of the HTD belts circa 1985-86, so the rubber industry has not invested in upgrading the old trapezoidal belts. They still use old HCR rubber and construction. The only exception is JAE's Lotus belt. They work with Gates Racing to make trapezoidal 9XX belts in HSN rubber (~1995 technology). It's better than the standard HCR belts, but still not modern day HNBR rubber. Cheap HTD belts in the Lotus size are still available in old-school HCR; but I strongly recommend that if you're going to make the upgrade to HTD, that you should spend just a few bucks more and use the later 1995-spec HSN HTD belt. No major rubber company markets a HNBR belt that will fit the Lotus 9XX. However, once again, JAE works with Gates Racing to produce a special run of HNBR HTD belts. They have Gates Racing's signature blue outer layer, so they're easy to spot. It's the best belt you can put on a 9XX. The downside... $165 each. If you're going to use the engine in competitive autocross, consider it mechanical insurance. If you go there, talk with me about how to tension it. The book spec doesn't work for the blue belt. Having said all that, I autocrossed my Eclat and Esprit S2 with the stock trapezoidal timing belt and never suffered a failure. However, I checked/ re-set the tension religiously, and replaced the belt often. I was always doing 'something' on the engines, so every time the belt had to be slipped off the pulleys for something, I replaced it. My belts didn't get very old. For trapezoidal belts, the standard service interval is 24,000 miles or 24 months, whichever comes first. Time is just as important as miles. Don't cheat on that. Regards, Tim Engel Last edited on 11-18-2015 06:38 pm by Esprit2 |
|||||||||
|
stevegarnjobst Member
|
Thanks again Tim! This thread is quickly becoming a valuable repository of build data. I'll see what kind of price tag Mike puts on the HTD conversion. It sounds like a "nice to have" upgrade, depending on the cost. It sounds like I'll have difficulty leaving Lotusbits without at least a few parts, as Mike appears to have a number of items on the shelf that are difficult to find anywhere else. |
|||||||||
|
stevegarnjobst Member
|
Stopped by Lotusbits for an extended visit this afternoon. Located in a rural area just Southeast of Coventry, the shop is an absolute treasure trove of hard to find parts for the Lotus 907/912 engines. Mike at Lotusbits was extremely helpful. We spent a good deal of time digging through his parts bins and discussing upgrade options for the Lotus engine in my Jensen Healey. I bought a couple hard to find items while at the shop - an Eclat/Elite airbox and a lightened steel flywheel. I also talked with Mike about various options for an EFI kit, and examined a couple engines with the Lotusbits EFI conversion installed. VERY nice package, with the cleanest, most secure crank sensor I've seen. It seems about as close to a simple bolt-on conversion as one could hope for. The only significant piece not in the kit is a fuel return line. -Steve |
|||||||||
|
stevegarnjobst Member
|
Esprit2 wrote:Steve, Tim (or anyone else who knows 907's really well), When I was at Lotusbits today, Mike showed me stock Jensen Healey and early Lotus 907 heads side by side. The Lotus heads had substantially larger intake ports (a lot more than the 1mm increase mentioned above). The Lotus and J-H heads had the EXACT same part number cast into the head, and Mike thought some later J-H's may have come with the Lotus head, as supplies of the J-H head ran out. Since it appears Lotus changed the port design without changing the part #, it sounds like the large port heads would be legal for me to run. Can anyone else confirm this? The larger port Lotus heads flow better, which would be useful. Last edited on 11-27-2015 12:27 am by stevegarnjobst |
|||||||||
|
Esprit2 Member
|
Steve, The number cast into a Lotus part is the raw casting number, not the finished part as used on the engine, or that you could buy. Besides the casting number, there was a machined bare head part number, and a fully built-up, ready to install part number. Lotus didn't fully machine the ports from small-as-cast to various finished sizes. They were used pretty much as cast. The original AP head's intake ports (AP was the first castings vendor) did go through a series of evolutionary changes (at least three that I know of) before the vendor change to the Zeus head with it's final port config (Zeus is the later castings vendor, circa 1993). The Zeus head is superior, but didn't come along until well after JH was out of production. It would require some fast talking to justify using one on a JH autocrosser. The early JH Mk I 907 did have the small ports, however, the later Mk II did get larger ports... the ones I believe are 1mm taller. Lotus produced the 907 through 1980, and late 907/ early 912 heads had ports that were larger yet. That may (??) be what Mike Taylor showed to you. The big port head will bolt right on. I don't know enough about JH to know how far their 907's ports went down that evolutionary path. But the last of the JH engines were pretty much the same spec as the Lotus 907s of the day, with the exception of carbs and distributor advance curves. JH & Lotus Strombergs used different needles and tuning. JH used DHLA 40 Dellortos, while Lotus used the larger 45s. Do you have pictures you can post of the two heads with small and large ports? Regards, Tim Engel Last edited on 11-27-2015 08:26 pm by Esprit2 |
|||||||||
|
Esprit2 Member
|
Steve, The current head gasket is the Goetze composite gasket (or JAE sells their own aftermarket clone). It requires the use of either Lotus' later upgraded head studs (Lotus Part Number B912E7029Z), or the ARP studs that are available for the 9XX engines, along with a significantly higher torque. The Lotus spec calls for the use of a Torque Angle Meter instead of a torque wrench. Use the following tightening procedure and notes: 1) Check that the cylinder liner nip is within spec: ... +.001 to +.005 inch (+ .025 to +.130 mm). 2) Use Lotus upgraded cylinder head studs (B907E0224Z) identified by a dimple machined into the top end. Tighten into the block (with oiled threads) to 37 - 41 Nm (27 - 30 lbf-ft). 3) Make certain all mating metal surfaces are absolutely clean and dry (wipe with brake, carb or contact cleaner). 4) Fit the composite head gasket DRY. 5) Put the cylinder head in place before oiling the washers & head stud threads and fitting the nuts. Tighten the nuts using a torque/angle gauge, in a sequence from the center outwards, in the following steps: i) 20 Nm (15 lbf-ft) initial pre-load via a torque wrench. ii) +75 Degrees iii) +40 Degrees iv) Wait 5+ minutes (longer is better) v) +20 Degrees The net result of Lotus’ torque angle spec is a higher final torque/ clamping force than was produced by Lotus’ original 70-75 lb-ft torque wrench spec. Do NOT consider the old spec and new spec as different but interchangeable... they're very different. I've had mixed results installing the composite gasket dry as instructed. I now prefer to apply a little Wellseal, or Permatex Aviation Form-a-Gasket around the oil passage between the block and head (apply to both sides of the gasket). In my more paranoid moments, I'll also apply a little around the full perimeter of the head & block, both sides of the gasket. That only addresses coolant and oil leaks. At the cylinder liner seal area, the gasket must be installed DRY. *~*~* If you use the ARP studs, then ARP specifies the use of a torque wrench, as follows: 6) Apply "ARP Ultra-Torque Fastener Assembly Lubricant" to the washers, bottom of the nuts, and the stud threads (the lube is included in JAE’s ARP kit). 7) Torque the nuts in several smaller steps to a final setting of 110 Lb-Ft. (arbitrary, but something like 50, 75, 100, 110, with the last step being small). With either procedure, torque the nuts from the center of the head outward, in a criss-cross pattern. *~*~* As mentioned in post #19, "IF" you don't replace the original low-spec head studs, then stay with the original 'Lotus' torque spec out of consideration for the lo-spec studs. You won't be getting the full advantage of the composite gasket, but you won't be over-stretching the weaker studs either. Note that the J-H head torque spec was too high, crushed the old gasket, and caused problems with blown gaskets. Lotus reduced the torque spec to a level that didn't crush the gasket, or over-stretch the studs. If you're going to stay old-school, it would be better to follow the Lotus torque spec instead of the one in the J-H Workshop Manual. Lotus Cylinder Head Torque Spec: (Tighten Cold, Oiled Threads & Washers) 70 Lbs-ft - Front & Rear Pairs 75 Lbs-ft - Three Middle Pairs And again, work up to the final torque in several stages. For your autocross engine, I strongly recommend that you replace the original head studs with either Lotus' later upgraded head studs (B912E7029Z), or the ARP studs. Regards, Tim Engel Last edited on 11-27-2015 11:51 pm by Esprit2 |
|||||||||
|
Esprit2 Member
|
While I'm on a roll, here's one more thing... The original steel-asbestos-steel exhaust gasket blows too easily (the ones between the exhaust manifold flange and the cylinder head). The later gasket Lotus used for the 910 Turbo is a 3-laminate stainless steel part that does not blow. I've even re-used them once or twice without experiencing any leaks. The gasket in Federal 910s was a 2-laminate. But a friend in the UK once sent me some 3-laminate gaskets that were available there, and they were wonderful. I contacted Lotus Cars USA (LCU), but they didn't know what I was talking about and never made them available on this side of the pond. I showed the 3-lam gasket to JAE, and they had them reproduced. The only difference is that the Lotus gaskets are crimped together around the ID, and the JAE version is secured together with eyelets at three ears near the stud holes. In rare situations, I've had one of the eyelets interfere with the manifold flange (the gaskets are designed for the 910, I'm using them on other engines). In that case, just remove the offending eyelet. Once the gaskets are installed on the engine, the eyelets are redundant anyway. When I was autocrossing 907s, the steel-asbestos-steel gaskets would blow way too often. After switching to the 3-laminate stainless steel gaskets, there was never another blown exhaust gasket. The original steel-asbestos-steel gasket "blows" (take that any way you wish). The Federal 910 2-laminate stainless steel gasket is preferable to the original 907 gasket. The Euro 910 / JAE 3-laminate stainless steel gasket is pretty much bullet-proof. Regards, Tim Engel Last edited on 04-29-2017 05:37 am by Esprit2 |
|||||||||
|
stevegarnjobst Member
|
Esprit2 wrote:...The early JH Mk I 907 did have the small ports, however, the later Mk II did get larger ports... the ones I believe are 1mm taller. Lotus produced the 907 through 1980, and late 907/ early 912 heads had ports that were larger yet. That may (??) be what Mike Taylor showed to you. The big port head will bolt right on. I didn't take a photo of the J-H and Lotus heads side by side, but I can probably ask Mike for a shot or two. Mike says the larger port heads were the only ones used on Lotus cars, some of which were produced at the same time as later Mk II J-H's, so it's quite possible some of the Lotus-spec heads were used on the last J-H's. I'm not quite ready to buy a big port head yet, but the possibility is definitely intriguing. -Steve Last edited on 11-28-2015 12:20 am by stevegarnjobst |
|||||||||
|
Esprit2 Member
|
Exhaust Manifold Gasket (between exhaust manifold flange & cylinder head) Original thru 1985 Steel-Asbestos-Steel Sandwich: A907E0004Z = JH 97263 - Martin Robey JH Parts Manual A907E0004ZC - 907 thru 1985 910LC - Same as above (Suffix letters are just an internal inventory control code) Later 1986-96 910HC & 912HC Stainless Steel, 2-Laminate A910E2235F - HC Carb, HCi Bosch F-Inj & GMP4 F-Inj A910E__?__F - Stainless Steel, 3-Laminate From a UK friend's source. JAE sells their own aftermarket version. *~*~* Stud - Cylinder Head to Block: A907E0224Z = JH 93576 - Stud, M12, Cyl Head/ Block, Orig. B907E0224Z - Stud, M12, 1993-on, Head to Block, Upgraded B-prefix stud is a direct fit into early 9XX engines, just stronger. Regards, Tim Engel Last edited on 11-28-2015 12:54 am by Esprit2 |
|||||||||
|
stevegarnjobst Member
|
More helpful info - thanks Tim! Here are a few more details on the Lotusbits EFI system. It uses Jenvey throttle bodies, typically 45mm for a stockish engine, and 48mm for a 2.2L/2.5L high compression engine. The custom intake won't fit under the J-H hood, so the kit would use a Lotus or J-H Dellorto manifold, depending on the head being used. The kit includes an ECU, wiring loom, coil pack, crank trigger, fuel pump, pressure regulator, distributor plug, and a few other bits. Lotusbits uses a DTA ECU that looks pretty decent. The S40 is the standard unit, which meets my requirements. The more advanced S60 or S80 provide more logging and features like launch control & flat shift. Mike recommends the Lotus Eclat/Elite airbox, which apparently produces the best power numbers. I picked one up while at Lotusbits, as the airboxes are apparently hard to come by. I also picked up a lightened steel flywheel, which is a beautiful piece - just the right weight, nicely finished & balanced. Lotusbits also has a very nice looking header & exhaust system for the J-H. I'm particularly interested in the header, as it's a 4-2-1 design that should produce better mid-range power than the common 4-1 header. It also assembles in a way that's supposed to make installation a bit easier. I'm curious if anyone has first-hand experience with the Lotusbits header on a Mk II J-H? The exhaust system also looks to be a nice piece, although the mufflers use some fairly large cans, so I'm a bit concerned about ground clearance for the front can. Mike claims 95dB with the full system, and about 100dB without the rear can. -Steve Last edited on 11-29-2015 03:59 pm by stevegarnjobst |
|||||||||
|
NigelK Member
|
Hi Steve I've got the Lotusbits big bore exhaust system fitted to my GT and I can't recommend it highly enough. I don't compete in my Jensen, but the exhaust certainly frees up the engine and also quietens it down a lot when I'm pootling around town. I've had no issues with ground clearance with the front silencer (which replaces the front and middle silencers in the stock system). I also second Mike's view re the airbox - with an unrestrictive exhaust system the stock (muffler type) airbox is restrictive, even with a decent K&N filter. Mike found this when dyno testing my GT after upgrading the engine to Lotus spec 10 - replacing the stock airbox with the Excel type increased bhp by over 20%. In terms of originality for autocross purposes, a few of the very last J-Hs (and a majority of the GTs) were fitted with the T75 engine with the Eclat/Elite airbox, so you might be alright. Hope this helps. Best wishes, Nigel |
|||||||||
|
stevegarnjobst Member
|
Spending a little time on interior modifications this weekend. First, those floor mats were the easiest 11 lb weight reduction ever. Would never have guessed they weigh that much! Second, I pulled out the stock seats, which weighed in at 28.4 lbs each, with sliders. The Kirkey Pro Street Drag seats I'm using should come in around 20 lbs each, with mounting hardware. For mounting, I'm just using a pair of 15" x 15" aluminum plates mounted to the stock seat mounting points. This will give me a flat, stiff base to mount the Kirkeys exactly where I want them. I have some Corbeau dual locking sliders to provide adjustability. I also pulled off the Series 2 bumpers, which weighed in at a whopping 111 lbs, versus 29 lbs for my Series 1 bumpers. Last edited on 12-14-2015 05:15 pm by stevegarnjobst |
|||||||||
|
stevegarnjobst Member
|
I received a box from Gripper today. Inside was a shiny new limited slip unit for the J-H! I understand all five units produced by Gripper in this batch have been sold. I'm glad my efforts with the fine folks at Gripper helped make this upgrade a reality for a few lucky J-H owners! -Steve Attachment: Gripper LSD smallest.jpg (Downloaded 203 times) |
|||||||||
|
Esprit2 Member
|
Steve, Nice looking diff, but... have you ever autocrossed a lightweight car with a limited slip differential? 1) Limited slip under power will tend to make the car go straight, meaning you can't start to feed in the throttle until you have the car straightened out. Is Phil Ethier still autocrossing? Ask him about the LSD a PO had put into the Lotus Europa he used to autocross. He put regular gear oil in it, and just prayed for the day the clutches would wear out. When they did, the car got much better at handling the tight courses. 2) With the near-stock 907's modest torque, I don't think you'd have too much difficulty managing the wheel spin with an open diff. With a hot rod 2.2 or 2.5 it would be a different story. Regards, Tim Engel |
|||||||||
|
stevegarnjobst Member
|
Esprit2 wrote:Steve, Yup, LOTS of experience with lightweight autocross cars - both with and without limited slip differentials. When set up properly, a car with a limited slip will virtually always be faster than one without a limited slip, assuming the vehicle has sufficient power to spin the tires under acceleration. The issues you describe are definitely a problem with some limited slip designs, or with limited slip units not properly tuned for autocross use. For autocross, what you want is a differential that behaves like an open diff on corner entry, which minimizes/limits the understeer behavior you describe. However, you want the limited slip to distribute power between the drive wheels when accelerating, such as on corner exit. With the Gripper unit, diff behavior is adjustable, via ramp angles. The unit permits different diff engagement settings for corner entry/deceleration and corner exit/acceleration. I'll be running the diff with settings appropriate for autocross use. On a related note - it's fairly common for road racers with older low-powered British cars to run "welded" diffs, which essentially creates a locked differential. Welded diffs display precisely the behavior you describe. It's very difficult to drive a car with a welded diff on an autocross course, as you literally have to break the tires loose and slide the car around every tight corner. Last edited on 02-07-2016 01:41 pm by stevegarnjobst |
|||||||||
|
pmebill Member
|
Greetings Steve! I'm also going to be running my JH (74) in SCCA AutoX FSP class this season. I've been away from the JH game for a good 4 years now, but just picking up my replacement in a week or two. Already has Dellortos, Header, upgraded shocks and sways. Also a roll bar. I'm going to read through your thread in more detail later on today/tomorrow. Perhaps we can compare build/prep notes and meet up at Nationals! :) ~Bill |
|||||||||
|
stevegarnjobst Member
|
It's been quite a while since I updated this thread. Unfortunately, the J-H's season was cut short last year, due to one of those stupid cast iron tappets flying into small pieces at the wrong time. The car has been sitting on the trailer until now, waiting for sufficient funds to finance the repair. The good news is I just ordered a bunch of parts from LotusBits, including a re-built head, exhaust header, and a complete EFI system. I'm particularly excited about the EFI system, as I've seen the LotusBits kit in person, and it's a very nicely sorted package. I can hardly wait for a modern fuel & ignition system that will deliver reliable performance and not experience fuel starvation on long left-handers. While the engine is out of the car, I'll install the lightweight flywheel and take a look at the transmission, as the 1-2 shift currently requires much finesse. The initial round of suspension upgrades and weight reduction are pretty much complete, so I'll be impatiently waiting a couple months for a shipment from the UK. -Steve Last edited on 04-28-2017 02:37 am by stevegarnjobst |
|||||||||
|
Esprit2 Member
|
Steve, What will fuel injection do to how the SCCA classes your car for autocross? If you had another stock head, would you install it just to get the car running until the Lotusbits shipment arrives? There's a fellow south of Victoria who has a JH engine for sale. I've not checked in with him for a while so I don't really know if he still has it, but I could give him a buzz if you're interested. Also, there's a fellow in the Brooklyn Park area who has a seriously ported Dave Smith head for sale, along with a set of DS2 cams to go with it. Fresh as received, never installed. DS2 cams are a step hotter than the Lotus 104 cam. That one wouldn't be cheap, but it would sure be effective. Regards, Tim Engel |
|||||||||
|
stevegarnjobst Member
|
Tim, Fuel induction & ignition are mostly unrestricted in Street Prepared, so EFI is probably the single most significant engine upgrade I can make within the rules. Unfortunately, I have to keep the stock low-compression pistons & cams, so performance gains will be modest. However, I won't miss dealing with finicky carbs - especially as the weather changes. I also had major issues with fuel starvation on the Strombergs on sustained left-hand turns. I could convert to Dellortos, but EFI offers a better (if more expensive) solution. One other upgrade I'm planning for the EFI is a new fuel tank. The rules provide some leeway for replacement, in cases where new OE parts aren't available, so I'll be installing a new tank with AN fittings that match the Aeroquip hardware used on the LotusBits system. Regarding the extra stock head, I'm a bit leery of those stock cast-iron tappets, after having one come apart on me last year. :( Last edited on 04-28-2017 01:57 pm by stevegarnjobst |
|||||||||
|
Esprit2 Member
|
I'm surprised fuel injection is such an open option. How are your cam's timed. The early J-H timing was 115 IN / 115 EX, and that reduces output by 10 Hp. Later it went to 100 IN / 110 EX. Both of those are emissions settings, and not desirable. The design-correct C-cam timing Lotus used in the early 907 is 110 IN / 110 EX. Does Street Prepared restrict the cam timing to stock, or can you make adjustments? At least update/ backdate? If that's not a problem, then try re-timing the stock C-cam to at least the design-correct 110 / 110, or more aggressively to 104 MOP IN / 110 MOP EX. Unfortunately, the latter would require a new 104 MOP green-dot pulley for the intake, and they're expensive for what you get. Maybe Mike Taylor can set you up with a serviceable used one. 115 and 110 co-exist on the same pulley, whether both are marked or not. Not that I would ever suggest cheating in anything but the holy NASCAR-biblical sense, but the C-cam has 272 degrees of duration, and the 104 cam has 272 degrees of duration. The devil is in the details... just sayin'. You're right to be concerned about the cast iron tappets. I've seen way too many cracked ones in recent years. Steel replacements are available, but a set of 16 gets expensive. On the other hand, one broken tappet in a running engine gets very expensive in a heartbeat. But then, you now know that... tell the others. Regards, Tim Engel Last edited on 04-28-2017 07:09 pm by Esprit2 |
|||||||||
|
RobInSanFrancisco Member
|
Hi. I would be interesting in your experience changing to earlier bumpers. What was involved? Thanks! |
|||||||||
|
stevegarnjobst Member
|
The rear bumper was a simple bolt-on swap. I didn’t get all the necessary brackets for the front, so I had to fabricate a couple parts. The biggest issue was finding steel bumpers in decent shape. I didn’t care about show-quality looks, so I had the bumpers cleaned up some & powdercoated black. I did buy a fresh set of rubber rub strips from Delta, to make them look a bit more tidy. |
|||||||||
|
RobInSanFrancisco Member
|
Thanks Steve, so, if I found a the number with the original brackets for Mk I, they would basically bolt right on? Because I read somewhere the body changed and it was not so simple. Simple would be great... I'd be happy with painted bumpers. My car is black so it would look fine. |
|||||||||