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| cam carriers SB 74-23 modification | Rate Topic |
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| Posted: 02-24-2020 03:21 am |
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1st Post |
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Pricelessjunk Member 
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I'm in the middle of my valve adjustment / re-shimming and I saw the note in a recent post about SB 74-23. I can't find the service bulletin right now but I remember it was to that the cam carrier oil passage hole needed a 31/64" counter-bore so an o-ring could be placed to provide sealing when going from a gasket to just using the anaerobic (518) between the cylinder head and the cam carrier. Well, when I removed my cam carriers, which had what looked like a factory paper gasket, one carrier looks like it has a counter bore and one doesn't. Question 1) Neither of them leaked at all so I'm wondering why or if I need to modify the carrier and use the o-ring or not. Question 2) See attached picture, Does the one look like its already been cut? Question 3) What it the process for cutting a 31/64" counter bore for the oil passage o-ring? thanks in advance. Attachment: Cam Carriers Oil Passage.jpg (Downloaded 140 times)
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| Posted: 02-24-2020 06:47 pm |
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2nd Post |
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redracer Member
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The paper gasket acted as the seal at that high pressure point, whereas Loctite #518 does not, so therefore you'll need both cam housings falt bored for the neoprene "O" ring. Dave Ban at one tim eused to sell something for this, but I had my own made( MSC and/or McMaster-Carr has correct sized bores with a pilot attached). At the moment, I do not have an easy way to post pix on this site, unlike personal emails. (i am not the prolific typist, info guru that Tim is, so maybe he has some "ready" photos) I will need to take many photos and download them onto my computer, but frankly, I am REALLY STRETCHED VERY THIN right now. People are welcome to call me or personally email me for faster info: bruce RedRacerbm@gmail.com (404)261-2552
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| Posted: 02-24-2020 11:06 pm |
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3rd Post |
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Esprit2 Member
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Pricelessjunk wrote:(Snip)... when I removed my cam carriers, which had what looked like a factory paper gasket, one carrier looks like it has a counter bore and one doesn't.I downloaded your photo and blew it up to full screen. As far as I can tell, neither of the cam carriers has the specified counterbore. One appears to have a slight countersink ('sink', not 'bore'), but that's not what is required. A countersink is a tapered recess around a hole. The tapered hole accepts the tapered bottom of a flathead screw. Or, it just serves as a 'funnel' to help parts slip into the hole. A counter bore is cylindrical. It has straight up & down side walls (a cylinder) with a 90 degree corner at the bottom, and a flat floor. It's a counter-square, not a counter-taper. When you see it on the bottom of a cam carrier, it's a real cut hole, not a bit of a taper leading into a hole. Am I making any sense? Cutting the counterbore isn't something you should try with a hand-held drill motor. Back in the day, a special service tool was issued that was essentially a 31/64" end mill cutter with a 11/32" pilot drill. Then a collar around the outside of the end mill was set to stop the cutter at a prescribed hole depth... hard to make a mistake. The drill bit fit into the existing oil hole, dress-cutting the bore slightly for the correct fit with the roll pin that would be fitted, then the end mill cut the counterbore. As the end-mill cut into the cam carrier, the collar would contact the carrier, stopping the cutter at the correct depth. The depth of the c-bore is important, so just winging it on a drill press is not a good idea. If it's too deep, the O-ring will not be compressed addequately to form a good seal. Too shallow, and the O-ring will interfere with the cam carrier fully seating on the head. It needs to be 'right'. I'd recommend that you take the cam carriers to a machine shop and have the work done properly in a vertical mill... unless you happen to have one in the corner. When properly cut, the counterbore will be: ......... SPEC METRIC.. / Calc'd Inch Decimal Dia .. 12.30 -12.44mm/ 0.48425" - 0.48976" (service tool was a 31/64" end mill cutter with a 11/32" pilot drill). Depth 1.20 - 1.30 mm / 0.04724" - 0.51181" The O-ring is Lotus part number: A907E6202Z. Two are required, one per cam carrier. Sorry, but I don't have the J-H part number at my finger tips. Sorry, but I don't have a spare cam carrier with the counter-bore laying about (mine are all in engines), so I can't send a photo at this time. However, tomorrow evening I 'may' be going to a friend's shop to help with a Lotus Esprit project, and I'm quite certain he has a few stray cam carriers. I'll take a few photos. BTW... one of the driving reasons for going gasketless was that the original gaskets would soak up oil, saturate, and essentially become a wick... ie, it promoted the oil leak. Regards, Tim Engel Last edited on 02-25-2020 12:26 am by Esprit2 |
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| Posted: 02-24-2020 11:22 pm |
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4th Post |
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redracer Member
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Tim: Good timing! I just sent the 3 photos from Bulletion 74-23, so he hopefully will have all the info he needs. thanks for posting, bruce
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| Posted: 02-25-2020 01:40 am |
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5th Post |
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Pricelessjunk Member
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Perfect! Bruce and Tim, Thank you both so much. Now I know the next steps - find a competent machine shop, have the counterbores cut to the specs and get the O-rings. I couldn't do it without the help of the incredible knowledge base on this forum. Thanks again. Tim Hendricks
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| Posted: 02-25-2020 01:58 am |
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6th Post |
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Esprit2 Member
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Just to be clear... On top of the cylinder head, where the cam carriers go, at the front, there are two roll pin/ dowels sticking up. One per cam carrier. They are both the oil transfer tubes, and dowel pins that locate the cam carriers. When the gaskets are eliminated, a rubber O-ring is installed over each of those roll pin/ dowels. But the top of the head is flat, so the O-ring just sits on top. It would get crushed if an 'old' flat-bottom cam carrier was bolted on. A 31/64" diameter counterbore needs to be cut 0.050" deep into the bottom of each cam carrier, concentric with the oil passage that mates with the head's roll pin/ dowels. That gives the O-rings someplace to go. But it's a snug 'squish' fit in order to form a good seal with the O-ring. O-rings should not be installed dry. In this case, instead of oil, I prefer to rub on a thin smear of Hylomar AF (Advanced Forumla). Plain old Hylomar Universal Blue will work. AF just has a longer working time, so it's easier to use. As I told Tim in a PM, when installing the cam carriers, do NOT use the torque spec given in the J-H Workshop Manual... it's too high, and you risk stripping the aluminum threads in the head (ie, pulling the studs out). Instead, use the Lotus torque spec: 14-16 Lbs-ft with clean dry threads. Regards, Tim Engel
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| Posted: 02-25-2020 07:52 pm |
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7th Post |
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chuckcm14 Member
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Tim, It's me again. Question for JH 20152. I pulled the intake cam housing carrier from the engine. The oil feed hole has not been reamed out like the one on the removed exhaust carrier. The exhaust carrier hole is 31/64 x .0052 deep. All that was there was the oil soggy gasket as found on the exhaust carrier. No o-ring was found in the exhaust carrier or in the head. Will not use gaskets during installation.I assume I have to ream out the exhaust carrier oil feed hole to the correct size. Then install O-rings and 518 during installation of the carriers to the head. The intake carrier has only one area (sprocket end) routed out. I assume done for more oil drainage. The exhaust carrier has both ends of the carrier routed out. Q. Should I route out the intake carrier (thrust plate end) like the exhaust carrier (thrust plate end). Thanks Chuck.
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| Posted: 02-25-2020 10:07 pm |
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8th Post |
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Esprit2 Member
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Chuck, I'm not following your descriptions, so please post pictures so I can see what it is that you have. I'm not sure how to make it more clear. Each cam carrier has only one oil feed hole, it's at the front, and it slips over the roll pin at the front of the cylinder head. There should be a 31/64" diameter x 0.050" deep counterbore around that hole, on the bottom side of each cam carrier. In stock form, none of the other bolt holes or drain holes are to have any sort of counterbore or countersink around them. If holes at the back end of your exhaust cam carrier have been "routed out" (?), then someone has been screwing around with it. No, don't follow their example, don't "route out" any holes at the thrust plate end. The only holes that require any modifications are the oil transfer holes... one at the front-center of each cam carrier. Regards, Tim Engel Last edited on 02-25-2020 10:08 pm by Esprit2 |
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| Posted: 02-25-2020 10:12 pm |
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9th Post |
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redracer Member
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Chuck: Your INtake cam housing is a later(and much preferred--after engine #3846); your EXhaust cam housing is from an earlier engine(#3846 & earlier) and should be discarded for 2 reasons; the first is that the rear oil drain hole was "plugged" up so oil would sit in the housing for engine starting and not gall the aluminum housing due to no oil, and secondly, the 5 bearing surfaces for the later housings were 0.001" larger for the same reason. (advise you toss the EX and get a later one). Yes, you will need to do the "spot" facing for the 2 oil feed holes in the front.best, bruce
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| Posted: 02-28-2020 06:42 am |
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10th Post |
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Max_dvdt Member
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Looking for a suggestion on the o-ring. Is the McMaster carr https://www.mcmaster.com/9464k44 a good suggestion? Viton - oil compatible and good to 400F
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| Posted: 02-28-2020 06:43 am |
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11th Post |
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Max_dvdt Member
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Bruce- How can we tell which cam housings we have pre or post #3846? Thank you
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| Posted: 02-29-2020 02:43 pm |
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12th Post |
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redracer Member
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As I stated in the previous post, if there is a large oil drain hole(similar to the front drain hole) in your cam housing, that is from an earlier engine. Many owners needed to have their housings replace due to lack of oil in the cam housing(mainly leaking from the cam covers--get the good replacement ones) and the earlier engines were more available and used, even though each of the 5 bearing surfaces were 0.001" smaller in diameter. I don't know for sure, but the smaller may not have been a problem if better cam cover gaskets had been available, but the rear oil drain hole should be "plugged" if a newer style one is not available(don't ask me how to do it)
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| Posted: 02-29-2020 02:48 pm |
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13th Post |
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redracer Member
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The O.D of this is larger than the spotted hole(31/64") and will NOT work as it will get "pushed" onto the main surface of the interface. Basically, a smaller one that the ID(I don't have the exact size handy, but will look later) whose ID just fits over the pressure hole will get crushed and still be entirely within the spotted surface and NOT push out onto the main interface
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| Posted: 03-16-2020 02:40 am |
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14th Post |
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Pricelessjunk Member
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Just a follow up from my experience with the valve adjustment procedure. I don't think this was ever done to this engine prior and I want to give a a big THANK YOU for all the good advice from Tim Engle (Esprit2), Bruce (Redracer) and Greg Fletcher (JHPS). Once I knew what I had to do everything went well and it was actually an enjoyable process. I had the cam carrier oil passage port counter bored by a local machine shop ($40), calculated the size of the shims I needed, got the shims and oil passage o-rings from Delta and since I had to measure all the clearances anyway I got a set of 107 Cams (JHPS, thanks Greg) along with a set of 104 MOP (green dot) cam pulleys and put it all back together. Wow, I'm smiling now. Just as advised the 107 cams run smooth and pull nicely through the gears - I'd say they are a nice upgrade and worth it. Attached are some pictures of the cam carrier modification (oil passage counter bore and o-ring installation) that was required since it hadn't previously been done. I used the 518 Anaerobic sealer and there was no noticable clearance change after torquing the carriers down. Attachment: Counter bore cam carrier and shim adjustment.jpg (Downloaded 78 times)
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| Posted: 03-16-2020 03:03 am |
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15th Post |
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redracer Member
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Congratulations; happy you've got it back together in good order. Post some pix of your steed!
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| Posted: 03-16-2020 07:20 am |
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16th Post |
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Esprit2 Member
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Good job. I'm glad you got it all back together. Now, looking back on it all from a different point of view, it's not really all that difficult, is it? Congratulations, Tim
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| Posted: 03-17-2020 04:35 pm |
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17th Post |
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noomg Member
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Priceless, You're probably right about this being the motor's first valve adjustment. The manual says check every 12K and I'm not sure how many miles you could go before a valve adjust is actually required. I'd guess by the time it needed an adjustment the car was well out of warranty and having it done was not cheap. I did mine at about 80K and I don't think it had been done before either. My clearances were out but not way out. Smog testing was what compelled me to do the adjustment, to stay as close to spec as possible. As Tim says, it's not a difficult job, however it is a big job and while I might say it was satisfying I'd be hard pressed to use the word "enjoyable".
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| Posted: 03-17-2020 09:18 pm |
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18th Post |
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Esprit2 Member
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The spec valve clearances are stated as a range, typcially two thousandths wide. Lotus specs the clearances as: 0.005"-0.007" Intake 0.010"-0.012" Exhaust The clearances always close-up (get smaller) with use/ wear, and the lower spec value is the 'Wear Limit', or 'Service Limit'. Shim to the top of the range in order to enjoy the most drive-time before having to re-shim the clearances. If you shim to the bottom of the range, you're technically within spec. The only value in that is being able to say "I did it correctly" in some pedantic, argumentative sense. The reality is that if you shim to the bottom of the range, then by the time you drive out of the shop, you're due for a re-shim. You could keep yourself really busy that way. I'm not certain of the J-H service interval without looking, but Lotus specified 'checking' the valve clearances every 6000 miles, and only adjusting as necessary (ie, at or below the lower limit). If you shim to the top of the range, you can probably expect to get 18,000 miles before needing to shim again. But don't lock-onto any mileage as the limit. Check the valve clearances, and re-shim when they reach the bottom of the spec range. Too-tight clearances put the valves at risk of being burned, negativelly affect how well the engine runs, and causes elevated exhaust emissions. If the car must pass an annual emissions inspection where you are, and it has started failing lately, one of the items to check is the valve clearances. Regards, Tim Engel Last edited on 03-19-2020 12:13 am by Esprit2 |
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| Posted: 03-17-2020 10:50 pm |
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19th Post |
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Pricelessjunk Member
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I was afraid I would here valve train clatter if there was too much clearance but I adjusted to .007 on the intakes and .012 on the exhausts. I did this with a standard feeler gauge where the .007 slide in but the .008 was a no go. Same for the exhaust where the .012 slide in but the .013 was a no go. I figured with the gasket sealer it might lose a little clearance but once torqued down I got the same results. I have to say it sounds great! No tapping or clatter like I previously had and definitely runs better! While there are always small challenges, I take my time and actually enjoy the process. It's part of the fun of a classic British car. I rescued JH # 10626 (built 11/10/72) about 4 years ago. The original owner parked it in 1980 with just 22k miles. I brought her back to life (every nut and bolt) and enjoy driving and showing and there's always lots of interest. I have owned several Jensen Healeys over the years - worked at Manhattan Beach Imported Cars in the late 70's and it was love at first sight. So after many years of not having a JH I'm enjoying every minute and I think JH # 10626 is too! Attachment: 72 JH 10626.jpg (Downloaded 64 times)
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| Posted: 03-18-2020 01:19 am |
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20th Post |
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redracer Member
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Manhattan Beach! I still have about 2-3 T-shirts from there that I got in the late '70s!(red % yellow). Maybe I even talked to you on the phone then--small world!
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