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| Valve Clearance | Rate Topic |
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| Posted: 02-09-2020 05:21 pm |
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1st Post |
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chuckcm14 Member
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JH #20152 rubber bumper born 2/75 engine B74 036394 purchased 11/19. Car is in vg shape no rust. I have been doing various projects, electrical, window seals etc. Do to small leaks I decided to replace the cam cover gasket with new rubber ones. Checked the valve clearance and found that both inlet and exhaust valve clearances were below min but consistent. Clearances below min of .005 inlet requirement are measured at .003 to .004. Clearances below min of .010 exhaust requirement are measured at .006 to .008 One of the previous owners rebuilt the engine with high compression pistons (9:5 to 1), head rework and performance cam installed and other items. Q: Would the performance cam be the reason for the clearances being below min requirements? Q; I assume I have to change the shims so what would be the best clearances to accomplish. Min of .005 for the inlet valve and max of .012 for the exhaust valve? Q: Since none of measurements are above min I assume I can measure each shim where needed and replace it with a shim .xxx size less to obtain the larger correct clearance. Appreciate any comments. Chuck Mcdonald
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| Posted: 02-10-2020 09:10 pm |
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2nd Post |
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Esprit2 Member
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Q1 - No, a performance cam wouldn't be the reason for 'tight' clearances. Q2 - Use the clearances given in the Workshop manual... 0.005" - 0.007" Intake 0.010" - 0.012" Exhaust Q3 - Yes. Measure each valve's clearance, and subtract that from the MAXimum clearance (TOP of the spec range). Add the difference to the current shim's measured thickness to determine the 'gross' thickness for the new shim. Finally, subtract the film thickness for the sealant that will be used between the cam carrier & head. The final total is the 'net' thickness you should use for the next shim. The sealant that is applied between the cam carriers and the head has a squished/ cured thickness. If you carefully shim all the valves to the tops of their ranges using 'dry' trial assembly steps, then when the sealant is applied during final assembly, it's film thickness will 'float' the cam carriers that much off the head, and increase the valve clearances by a similar amount. Typical film thicknesses are: 0.0015" - Loctite 504, original sealant - still available, but better options are no available. 0.0010" - Wellseal or Permatex Aviation Form-a-Gasket - pretty old-school. 0.0005" - Modern anaerobic sealants, like Loctite 518, Permabond A136, Permatex Anaerobic Gasket Maker (518). The anaerobic sealants have been Lotus' spec since around 1980. J-H owners would be well advised to use the later sealant. "Dry Assembly" means a trial assembly done without applying any sealant. "Dry"-shim the valves to less than the top of the specs by the film thicknesss of the sealant you will be using. I strongly recommend using a modern anaerobic sealant, and my personal preference is Loctite 518. In that case, the film thickness is 0.0005", so Dry-shim the valves to: Dry Target . . . . . . . . . . . . . . . . . . . . . . . . . . . . Final Result 0.0065" Dry, plus 0.0005" film during final ass'y = 0.007" final clearance - INTAKE 0.0115" Dry, plus 0.0005" film during final ass'y = 0.012" final clearance - EXHAUST The valve stem will hammer a depression into the center of the shim. So the shim's "working" thickness is measured with a micrometer WITHIN (!!) that depression. A micrometer's round 'rod' anvil will fit into that depression and give an accurate measurement. The jaws of a caliper will bridge across the depression, and incorrectly measure the thicker part of the shim surrounding the depression. Measuring the thicker outer perimeter, or measuring with a caliper will give a false reading. USE A "MICROMETER" to measure the center of the shim. If you re-use old shims (perfectly acceptable), make certain that the side with a depression goes down against the valve stem. If the depression is installed 'up', then the tappet will bridge across it and result in an excessively large clearance. If the depression is installed 'down', the valve stem will fit into the depression and use the shims 'working' thickness to produce the correct valve clearance. Valves that are clearanced to the tops of their ranges will run with a certain amount of "clatter"... they're not quiet. That's NORMAL for all solid-lifter engines. As the clearances close-up with wear, the valves start to run more quietly. That may sound nice to your delicate ears, but "quiet" is telling you there is something wrong in the valve train. Check it out and fix it. The valves need to be talking to you. *~*~*~* It's best to shim the valves to the top of each range. That will give the longest service interval (time or miles) before the valves need to be re-shimmed again. But doing accurate work, and getting all 16 valves set to their max spec is laborious, time-consuming work. Many mechanics split the range, and figure that any clearance between the mid-point and the top of the range is good enough. But each range is only 0.002" wide, from Max to Min/ Service Limit. If they shim the easy/ lazy way, and send you down the road with only 0.001" of wear remaining before the valves need to be re-shimmed, then they're cutting the service life in half before you have to come back and pay them to do it all over again. If you're doing the work yourself, I strongly recommennd that you take the time to shim all the valves to the tops of their spec ranges... 0.007" Intake and 0.012" Exhaust. Done that way, you should have something like 18,000 miles before you'll have to do the job again. *~*~*~* The valves live in a very hot environment... especially the exhaust valves. Their only opportunity to cool down is while they're closed and in contact with the water cooled head. The "closed duration" is very important to the valve's longevity. Valve clearances influence the time-duration that the valves are closed, and tighter/ smaller clearances mean the valves are closed/ cooling for LESS time... the valves will run HOT. In normal use, the valve heads tend to hammer their way up into the valve seats... it's called Valve Recession. As the valve recedes up into the head, the upper end of the stem gets closer to the cam lobe, so the clearances get smaller. That's normal wear, and the valve clearances are supposed to be re-shimmed to spec periodically. Check the clearances at each scheduled major service interval, which is specified at every 6000 miles. Adjust the valve clearances as required... meaning 'IF" the clearances are below the minimum spec. If the valves are correctly shimmed to the TOP of the spec, then it will not normally be necessary to re-shim at every 6000 mile service interval... more likely every third interval, or 18,000 miles. But regardless of how long it has been since the last time the valves were clearanced, if you measure the clearances as at or below the spec minimums, then it is now time to re-shim the valve clearances... no argument. At your measured 0.003" - 0 .004" Intake, and 0.006" - 0.008" Exhaust, all of your engine's valves are w-a-a-a-y past due for being re-shimmed. Repeating... the spec clearance is: 0.005" - 0.007" - Intake 0.010" - 0.012" - Exhaust In each valve clearance Spec range, the smaller number is the "Service Limit", and the clearances are not supposed to below that. At 0.005" INT or 0.010" EXH, it's time to re-shim the valves. Allowing the clearances to close up any further than that (as your valves are now) is putting the valves at risk of over-heating or burning. Valve clearances also affect the points in crank degreess when the valves begin to open, or close. That alters the effective cam timing, and affects how the engine runs. A "serious" engine tune-up should start with clearancing the valves first, then tuning the ignition timing, and finally tuning & balancing the carbs. Regards, Tim Engel Last edited on 02-10-2020 09:29 pm by Esprit2 |
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| Posted: 02-11-2020 02:25 am |
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3rd Post |
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chuckcm14 Member
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Tim, Thank you very much for the technical response. Printed a copy of the response. Very thorough. I thought this would be the answer. I will be removing both camshaft housings and adjusting the valves myself. Never done a Lotus engine but I have done Ducati and other motorcycle engines with shims to obtain valve clearance. Removing the exhaust camshaft housing will make it easier to clean the flange where gasket sits. The PO used a paper gasket and lots of gay sealant. It still wept onto the exhaust manifold and into the spark plug port area. I am using the new expensive rubber gaskets and no sealant. Hopefully this will work. Afterwards I also will check the timing and adjust the carbs. The plugs showed the Dellortos are running to rich. Could be rich from the oval air cleaners (k&n type) which had a sponge type cover, then an inch thick layer of some type of sponge wrapping then the dust covers over that. Once again thanks for valuable info. Regards, Chuck McDonald
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| Posted: 02-14-2020 05:17 pm |
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4th Post |
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chuckcm14 Member
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Tim, I first removed the exhaust cam housing and naturally gravity took over and three shims hit the floor. Three stayed inside the vale stem retainers and others stayed on the face of the cam followers. I measured the shims in the dimple and found that the difference is .0003 lower than across the face dimension of the shim. Does not seem like much wear. If I use the sims I will flip them over. The engine supposedly has less than 3k since rebuild. The engine ran real good and no smoke of any kind so I did not do a compression or leak down tests prior to checking valve clearance. My error. It looked like black sealant was used for the cam housing to the head but it turned out to be a black gasket. I measured a crushed flat area on the gasket and it is .020 thick. Not sure what they did to end up with the valve clearances I measured. I found a bigger problem. There is a rusty crud build up in the valley below the side of one head hold down nut. I believe there was a coolant leakage at onetime. The next head nut over has a small green coolant puddle in the valley. I will be pulling the intake cam housing and the head assy to replace the head gasket. I checked the toque on the head nuts and they were at the top end of the spec or greater. Not sure what caused the leak past the studs in the head. Q1. When I install the shims is it ok to use an assembly lube on the sides (not faces) of the shims to hold them in place in the spring retainers during dry clearance trials Q2. Is a new head gasket from Delta or others ok for the lotus 907 or is there a better gasket. Especially since the compression ratio was stated to me to be 9.5 to 1. Q3. I want to check to see if a performance cams were really installed in the engine. Are there identifications to look for on the cams. I saw stamped on the cam non machined surface A 907E. Q4. Is there a way to identify if high compression pistons were really installed. Regards Chuck
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| Posted: 02-16-2020 03:30 pm |
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5th Post |
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chuckcm14 Member
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Esprit2 Tim Engel, I responded to myself in the 4th post in place of you. Would you look at the 4th post and respond to me regarding the info I found during exhaust cam housing removal. Thank you Regards, Chuck McDonald
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| Posted: 02-16-2020 08:27 pm |
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6th Post |
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Esprit2 Member
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Chuck, No, 0.0003" isn't a lot of wear in a shim, and they can be re-used with considerably more wear... a deeper pocket. They're almost new... consistant with only being run 3000 miles since the last rebuild. > If I use the sims I will flip them over. NO ! When you re-install USED shims, the dimple must go back DOWN against the valve stem. The stem will correctly fit into the pocket a stem created. A tappet's flat inside surface will bridge across a pocket, not touch the bottom of the pocket where you measured, and give an incorrect clearance (incorrect = not matching your calculations). > It looked like black sealant was used for the cam housing to the head but it turned out to be a black gasket. Very early J-H 907s used a thin gasket between the cam carriers and the head. A Tech Service Bulletin eliminated that gasket back in the day (early-mid 1970's) when Jensen was still in business, and all 907s should have been converted to gasketless long, long ago. The modification involved cutting a counter-bore around the oil passages at the front, between the head and carrier, so it's not a simple matter of deleting the gasket. An O-ring is to be installed in the counter-bores during assembly. Inspect your cylinder head. There should be a counterbore around the base of what looks like a hollow dowel pin. If it's not there, we can talk then. Deleting the gasket will result in the cam carriers sitting lower on the head by it's thickness. That will change all the shim thicknesses by the same amount. Have you just shimmed 'GASKETLESS' ? > I believe there was a coolant leakage at onetime. Well, that's not good. You'll have to get to the bottom of that issue. > I checked the toque on the head nuts and they were at the top end of the spec or greater. What torque spec are you using? The spec given in the J-H Workshop manual is not appropriate for use with any modern composite head gasket.... Lotus or aftermarket clone. Similarly, the original 907 head studs can NOT handle the torque for the modern gaskets. Replace the head studs with either Lotus 1993-onward B-prefix studs (B907ExxxxX), or with aftermarket ARP studs. Each stud option has it's own specific torque spec. The B-prefix studs look pretty much like the original studs, except that they have a semi-spherical dimple machined into their top ends. The ARP studs are black. Q1 - Yes, it's okay to use an assembly lube on the sides of the shims as you describe; However the mess would be difficult to control through multiple trial runs (you will only rarely hit alll the correct clearances in one try). The official approach is to buy small bar magnets and apply them to the tops of the tappets... the side-cheeks that stick out past the cam lobe. Then the shims will stick to the tappets when you lift the cam carrier off. In a running engine, all the surfaces of the tappets and shims get coated with oil, and that's what sticks the shims to the tappets in the first place. When I assemble the bits for a trial run while shimming, I lightly oil the top sides of the tappets... just a drop on a finger tip, and smear the tappets that are already in the spring retainers. As you have already experienced, the tappets will come off with the cam carrriers/ tappets, but won't stick there forever. When I remove the cam carriers, I pull & rotate inverted in one smooth move. You have no choice but to go straight up off the studs at first, but then immediately rotate the carrier inverted. One smooth motion that shouldn't take more than a second. Q2 - Lotus discontinued the original steel-asbestos-steel head gasket (S-A-S) in Jan 1993. To the best of my knowledge, the S-A-S gasket is no longer available from any non-Lotus sources. Lotus' replacement gasket has a crushed thickness that is 0.5 mm (0.020") thicker, which lifts the head off the block by a similar distance, reducing the compression ratio by about half a point. The stock J-H 8.4:1 compression ratio becomes 7.9:1. "IF" your engine has 9.5:1 pistons, their compression ratio is now 9.0:1. There are aftermarket clones of the Lotus composite gasket (at least one, maybe two). Very recently, I have been looking into whether the clone gasket's crushed thickness is the same as Lotus' gasket, but so far I don't have an answer. There's also some question if Cometic has a gasket that might have a different crushed thickness, but again, no answer yet. It's even possible that a Cometic gasket is one of the clone gaskets. Again, I'm just getting into that 'investigation'. If you wish to get the engine put back together now, Then you don't have any current gasket option that mimics the original S-A-S thickness. Your 9.5: compression will end up somewhat lower. There is a solution, but it won't be cheap, and will require a complete engine re-build. From Jan 1993, Lotus milled the block deck lower by the same amount that the new gasket was thicker. (0.5 mm) then set the liners deeper into the block by the same amount in order to maintain the correct Nip. You could take your bare block to a machine shop and have the same thing done to it. Short of that, your compression ration will drop about half a point when the modern head gasket is installed. Period. Q3 - Every cam manufacturer/ re-grinder has their own way of marking their cam products. I have no idea what to tell you about where to look for them all. A 'LOTUS' cam will have a A907ExxxxX part number cast into the body of the cam. That's the blank's number, and all Lotus cams used the same blank. After they're ground, another ID is added to the smooth front shank that you can see between the front of the cam carrier and the back of the cam pulley. C-Cam = smooth, no mark D-Cam = one groove cut all the way around the shank E-Cam = two grooves 104 Cam = 4444444.... stamped all the way around 107 Cam = 7777777... all the way around. For any of the other aftermarket cams, you would have to ask the seller or manufacturer. I've got no clue. Use a caliper to measure the total height of the cam lobe... the total egg shape from top to bottom. Then measure cross-wise to that to get the base circle diameter. Subtract to get the lobe lift. That will give you some clue whether the cam in the engine is stock, or something else. C-Cam = 0.340" - Stock J-H cam. D-Cam = 0.350" E-Cam = 0.344" 104 Cam = 0.410" 105 Cam = 0.433" - Lotus, Competition only, No longer available. 106 Cam = 0.450" - Lotus, Competition only, NLA. 107 Cam = 0.252" 108 Cam = 0.460" - Lotus, Competition only, NLA. DS2 Cam = = 0.415" Dave Bean BLL-107 = 0.375" Dave Bean BLL-104 = 0.420" Dave Bean BLL-105 = 0.425" Kent Cams BD4 = 0.431" = Cosworth BD4 Kent Cams L14 = 0.415" = Cosworth L14 Kent Cams L1 = 0.408" = Cosworth L1 Q4 - Get the engine together, then do a compression test. J-H & Lotus both used the 8.4:1 compression ratio, but J-H spec'd a cold compression test, and Lotus spec'd a hot test. They give different results. You can do a cold test on a non-functional engine, but a hot test is more representative of the engine's true operating condition... what's your priority? 8.4:1 cr - 7.58 - 8.96 bar .. (110 - 130 psi) COLD = Jensen-Healey CR Test Spec 8.4:1 cr - 10.2 - 11.6 bar .. (150 - 170 psi) HOT = Lotus CR Test Spec 9.5:1 cr - 11.2 - 12.6 bar .. (165 - 185 psi) Hot = Lotus only, J-H never used 9.5:1 9.44:1 cr - 11.2 - 12.6 bar (165 - 185 psi) Hot = Lotus only, 912LC 10.9:1 cr - 11.5 - 13.0 bar (170 - 190 psi) Hot = Lotus only, 912HC 7.5:1 cr - 8.8 bar (130 psi min) Hot = Lotus only, 910 Turbo prior to 1986 8.0:1 cr - 9.5 bar (140 psi min) Hot = Lotus only, 910 Turbo 1986-96 When doing the test, run the engine long enough to get up to full operating temperature (except JH, room-temp cold), hold the throttles fully open, and crank the engine at a minimum of 200 rpm until the pressure reading peaks and holds at a max value. In order to facilitate the fastest cranking rpm practical, remove all spark plugs, make certain the battery is fully charged, or use jumper cables to a running vehicle. If there's fuel in the system (ie, the engine is in running condition), then disconnect the ignition to minimize the risk of fire with the spark plugs removed (some fuel mist will spew from the cylinders with no sparkplugs installed). If the engine is in good condition (no other problems that could produce low compression readings), then the above range of pressures should give you an idea of your engine's current compression ratio. Later, Tim Engel
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| Posted: 02-17-2020 12:55 pm |
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7th Post |
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chuckcm14 Member
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Tim, Thanks for the info. I will review and contact you later. I am now not in a hurry to get it on the road. Chuck
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| Posted: 02-18-2020 01:44 pm |
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8th Post |
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chuckcm14 Member
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Tim, Could not find any of the supplied identifications on the camshaft collar. However stamped on the rear face of the camshaft behind the thrush washer location was DELTA 107. I talked to Delta and this camshaft has a lift of .361. That is about the measurements I made for the lift. At least this is not a radical lift. Thanks for the info. Chuck.
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| Posted: 02-21-2020 01:25 am |
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9th Post |
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redracer Member
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Chuck: there are quite a few tricks to getting the shimming correctly done(normally, a 12 hour job for me on a long timed running engine). Usually, you will make 3 tries at the correct shimming, with the 4th being your final installation. After buffing down the com followers, a good coating of MoS2 on the outside of them will prevent them from falling out in a vertical position. The "small drop of oil' onto the center internal bucket will give enough surface tension on a clean shim(do NOT coat the shims until the final installation) to remove the entire cam housing SLOWLY with the buckets & shims in place. You may wish to put a clean cloth in the oil galleys going to the sump since this is your first time, but do not forget to remove them before final installation. As for the head bolts, go ahead if you wish and replace them, but in the 20 or so engines I have rebuilt, I have never had a problem with them, including the high compression engines for the Huffaker car. (btw, I still have a bout 20 N.O.S. head gaskets--the SAS ones no longer available). Don't forget about sealing the cam housing oil feed hole by drilling and reaming the cam housing oil feed hole(J-H Bulletin #74-23) if they haven't already been done. As Tim said, use Loctite 518 for the cam hosing-to-head. best wishes, bruce
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| Posted: 02-21-2020 05:17 pm |
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10th Post |
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chuckcm14 Member
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Bruce (redracer), Thanks for the info on shimming techniques. You, Tim Engel and others have provided a wealth of knowledge to the message board users. Especially to newbies like myself to the Lotus engine. The cam is a Delta 107 and they told me the lift is .361. I saw elsewhere that this cam has a .375 lift. I removed a camshaft and put in on v blocks. I measured a consistent .375 lift. At least I know what cam is in the engine. I believe the engine incorporates SB 74-23. I am not sure what is in the SB, but it looks like the oil passages in the cam housing have been routed open. Looks like an oil feed hole in head has been filled. Not sure where the o ring is located. Next step I am doing is to replace the head gasket. With Tim's info the engine has the B prefix dimpled studs'. I will probably buy the complete top end gasket kit. Regards, Chuck
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| Posted: 02-22-2020 05:02 am |
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11th Post |
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CDA951 Member
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A trick that I learned from reading one of the later Lotus Esprit manuals as posted by Tim/Esprit2 was to use bar magnets (available at any hardware store), one across each pair of tappets/followers, which will ensure that they do not fall out when the cam tower is wiggled out, and the shims will stay stuck to the undersides. Works like a charm. Last edited on 02-22-2020 05:03 am by CDA951 |
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| Posted: 02-22-2020 05:01 pm |
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12th Post |
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noomg Member
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My hat's off to you Bruce, When I did my valve adjust I stopped counting after half a dozen times. I'd say it probably took me about 10 or 12 times until I was satisfied with the clearances and a lot more than 12 hours and I wound up with a sack full of extra shims.
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| Posted: 02-23-2020 02:03 am |
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13th Post |
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redracer Member
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thanks for the kind words, but I've probably done around a 100 or so, so I do have it "down" as one would say(have made a up a "shim" sheet for all the valves and have about 4000+ shims with a specially made numbered(1-8, EX & IN)wooden board to hold each shim in its designated valve.) I'm sure you would get it down to that with a little more organizing. The longest time is involved in CAREFULLY getting the old #504 or 518 off the cylinder head(the cam housing is not nearly as time consuming)
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| Posted: 02-23-2020 11:04 am |
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14th Post |
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mtechwim Member
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Thats Nice, do you have some pic’s of it?
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| Posted: 02-27-2020 05:00 pm |
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15th Post |
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redracer Member
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Please use my regular email so I can take photos and email them that way--light years easier than going through this site. bruce: RedRacerbm@gmail.com 404-261-2552 (if you want info faster)
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| Posted: 02-27-2020 07:46 pm |
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16th Post |
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mtechwim Member
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Hi Bruce mail is on the way, manny thanks
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