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| Valve clearances and Camshafts | Rating: 
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| Posted: 03-22-2007 04:37 pm |
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41st Post |
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Jensen Healey Super Moderator 
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Dan, if you remove the cam tower, rotate the shims and re-install it you will find the measurements may change. Adjusting valve clearances on the 907 is a black art. You will not want to do this again soon, so order the shims and shoot for the high side. Throw away any shims that have obvious indentations from wear. They may not seat correctly and clearances could change within a few miles of driving. When you get them all within range, goop the towers with Loctite 515 and watch all your measurements change again. I made 6 or 7 attempts before settling on "good enough". May the Lords Of Lucas be with you, Kurt
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| Posted: 03-23-2007 05:02 am |
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42nd Post |
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Dan Eiland Member
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Kurt, I placed a thin layer of Loctite 515 on the towers and then torqued them down and measured all my clearances. I then removed the towers and cleaned all the loctite from the parts and then re-installed the towers, torqued them down and measured all my clearances again. For what it is worth, there was no measureable difference. I admit I used my finger to spread the 515 and I admit I spread a very thin layer. I did not measure the thickness of the 515 that I removed but my guess----less than or equal to 0.0005". With this issue aside I made a list of all my clearances and all my shim sizes and then found all the sizes I would need to bring all the clearances into spec on the high end. I called Jim at DMS and placed my order this morning. In the mean time I went by our local speed shop and purchased a Ford style remote oil filter kit. Installed the engine part of the kit as soon as I got home from work. My parts from Dave Bean also arrived today ( just some special washers and gaskets for my Turbo Esprit cam housings). They also got installed when I got home from work. My engine is getting closer to being finished everyday. Of course every day I feel further and further from finished.
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| Posted: 03-23-2007 02:40 pm |
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43rd Post |
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DeDub Member 
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OK, being my first time at the "black art" of Lotus cam shims, it's obvious to me there's a fair amount I don't understand: I'm shimming an unknown, used, new-to-me motor I'm thrown in my fresh body. I've started it, it ran fine and didn't smoke, but because it may be in there for a year or two I thought I'd better check valve adjustment. It needed it; most exhausts were in the single high digit range. And there were gaskets under the towers. So I made some guesses, ordered up a bunch of shims in the 60s range and started the tedious process of learning how fast I can install and remove the exhaust tower. I'm not known for my small, delicate hands. All was going OK except for the last valve on the back of #4 which continued to have zero clearance no matter how small a shim I had in there. Finally I put in the tower with NO shim there and tried to measure that way but couldn't get 50 thou of stacked feeler gauges to bend enough to get a satisfactory measurement but it seemed to be in the high 40 range with no shim at all. I'm kinda stuck. The part that's got me in a mental whirlwind is that I remember, and my notes show, that I got a 9 thou feeler gauge in there the first time I checked them, before I ever took the tower off the first time, and when there was still a gasket under there. How could this be? I can't imagine anything I could have done that would have *raised* the valve stem and shrunk the clearance at least 20 thou. Visually, the stem does look higher than the adjacent and with the tower in, the bucked looks to be about 20 thou or so higher than the adjacent. FYI, none of the valve stem heights are very similar; obviously the PO didn't have a quality valve job done at some point. I don't want to pull the head for one lousy high valve on an engine I don't plan to have in there forever but even a 60 shim doesn't seem to have any clearance. Any ideas?
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| Posted: 03-23-2007 05:33 pm |
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44th Post |
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Jim Sohl Member
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David, Well... some warning signs seem to be present. If, as you say, the stem is visually higher than the others, then something has allowed that valve to recede into the seat. You state that the engine 'ran fine'. A compression check might suggest otherwise, or better still, a leak-down test. It will be very important to follow up on your wayward valve for several reasons: 1) valve trouble is always important; 2) 907's are difficult to work on (you know that first-hand) and owners (of course I mean po's) often neglect proper valve care; 3) 907's have a history of 'burning' exhaust valves; and 4) numbers one, two, and three sound like your engine. 'Sounds like off-with-the-head to me. Conceivably, some weird coincidence of warped castings could produce your symptoms, but I doubt it given that receding exhaust valves are relatively common in 907's and most 9xx Lotus engines for that matter. My advice then is double check and triple check the symptoms to try and find a cause that may suggest that a burned valve is not the problem. If you do have to remove the head, check the stem to guide clearance on all valves. If the valves wiggle around more than a few thousandths (with the springs off), it is highly indicative that a general overhaul is in your future. Also, assuming you do have a burned valve, the seat may be too far gone to rehabilitate. This will require close examination for the reason that 907 seats don't grow on trees. Try the usual suspects, DMS, Dave Bean, etc. Hopefully, you will be able to get things right without removing the head, but obviously, don't trust to luck with an engine that is expensive/difficult to repair even when the 'normal' repairs are indicated. It is my belief that a 907 properly used means high output at high RPM, things that stress valves and pretty much everything else more than your average street engine. Good luck! Jim. p.s. I have '73, '74' & '79 907's and an '84 910. All are high mileage and all have valve issues of one sort or another.
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| Posted: 03-24-2007 05:34 am |
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45th Post |
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DeDub Member
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Thanks for the response, Jim. I have 3 heads and I think I'll pull my two spares and look them over carefully as replacements. It's obviously a lot easier to set the valves with the head on the bench anyway. I'm flummoxed by the last valve and much as I want to button this puppy up, I can't so I guess I'll be learning about Lotus heads sooner than I expected to. Those exhaust nuts looks so damn fiddly and the intake's not much better. Oh, well, eh? David
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| Posted: 03-29-2007 04:43 am |
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46th Post |
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Dan Eiland Member
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Here is my progress report on shimming the valves on my engine rebuild. I now have all the exhaust clearances set at 0.012 and they went fairly easily. The intake valves are a whole different story. I can take the cam carrier off and put it back on without changing a thing and I get totally different measurements on some of the valves. I received a second order of shims from Jim at DMS and they should have set the clearances dead on to the specs on the high end but that did not happen. I have played around with the shims until I finally got all the exhaust clearances at 0.012 and stopped there for the day. The next day I went back and started working on the intake valves to see if I could get them to come into spec. No such luck. At this time I had all set to either .007 or .006 with the exception of two. I figured I would need to order two more shims and that would work. Well, I went out to the garage to check the intake clearances again and now one valve that was at .007 is at 0. All I can think is something got in the last time I removed the cam carrier. I've stopped for the evening and will call Jim tomorrow to order a few more shims to play with (sizes I don't have or I need extras of). This has been challenging to say the least and frustrating to no end, but a good learning experience. I know I'm very close to getting these clearance set just right, but then how do you make sure they stay at the same clearance when you go to mount the cam carriers for the last time? Last edited on 03-29-2007 11:43 pm by Dan Eiland |
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| Posted: 03-29-2007 05:37 am |
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47th Post |
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Dan Eiland Member
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After writing my last reply it hit me that one of the shims probably slipped out of place causing the clearance on one of the valves to go to zero. I ran out to the garage and removed the cam carrier and I was right. I put it back in place and everything is either .006 or .007 with the exception of two valves. I'll order new shims for the two valves that are still out of spec and that should take care of setting the valve clearances.
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| Posted: 03-29-2007 07:03 am |
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48th Post |
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DeDub Member
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What a pain, eh, Dan. I'm in exactly the same place. Just finally, after the better part of a day today, got the exhaust to all within one thou of 12. Good enough for me, but I ran out of shims for the intakes so I'm waiting on shims, too. IYR, I was having trouble with a few of my exhausts needing shims less than 60, one quite a bit less. I was about to pull the head when on a whim I pulled the towers off another parts engine I had and voila! there were a pair of reground 107s. So now all the shims I need are around 100 instead of 60s. Much better, and hopefully the 107s will the torque a help a bit on this bone stock motor. But as so many JHers have undoubtedly found out before me, this is not a job I want to do very often, at least in the car. David
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| Posted: 03-29-2007 08:03 pm |
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49th Post |
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Jensen Healey Super Moderator
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Hi David, Precisely why my 107 cams are sitting on the bench. I hesitate to even remove the cam covers that don't leak. You are very lucky to find the performance cams. If they are regrinds of stock cams they should work well enough with the stock 110^ pulleys even though Lotus used 104^. The true Lotus 107 cams have the keyways offset so don't mix and match JH parts with them until you have done your research. Hope to see you on the road soon. http://www.nobbc.com Kurt San Anselmo
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| Posted: 03-29-2007 11:52 pm |
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50th Post |
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Dan Eiland Member
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Yes David, this is a pain. It can make a sane person go insane. I have one valve with a shim that is 0.152 and has a clearance of 0.008. I do not have a shim that is 0.153 to close the gap so I do have a shim that is 0.154. This should bring the clearance into spec at 0.006. I install the 0.154 shim and my clearance is now 0.004. You tell me how that happened? Yes I checked the thickness of the shim. It is correct with a few ten thousandths. More shims on there way. I'm determined to get this right. Last edited on 03-29-2007 11:53 pm by Dan Eiland |
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| Posted: 03-30-2007 03:49 am |
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51st Post |
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DeDub Member
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Kurt, Your mention of using 110 pulleys for my 107 cams made me realize I didn't understand the subtle dynamics of all the cam timing threads I read on the different forums here. 104^ was talked about for the 107 cams and even a 100^, which is a long way from 110^. But my question is: why can't I use my stock pulleys that are both marked at 110 and 115^, but just line them up where 104^ would be? Any one reading this thread who has an opinion on this? David, only needing a windshield, air cleaner, and paint to put his JH on the road.
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| Posted: 03-30-2007 04:09 pm |
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52nd Post |
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Greg Fletcher Administrator 
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You can do that, but to get it spot on, you would need the later style adjustable pulleys- converting means changing all pulleys and using the uprated half-moon timing belt. It's all good, but expensive. The stock pulleys on the Jensen Healey are only keyed for one setting.
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| Posted: 03-30-2007 04:22 pm |
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53rd Post |
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Jensen Healey Super Moderator
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Hi David, You will find it difficult to adjust the pulleys except in whole tooth increments. The factory moved the keyway on the pulley to create the various degrees. Notice that the 110in and 115in are on opposite sides of the pulley. Each tooth of the 40 tooth pulley is 9^, but since the cams turn at half the speed of the crank, it represents 18^ of cam timing which is measured at the crank. The difference between 110 and 115 is less than 1/3 of a tooth. The simple answer is you have two options: use the 110 pulleys if you have reground early JH cams (A907E0351Y) or purchase adjustable pulleys and time them properly to 104^. For a full explanation of cam timing madness read this: http://www.jensenhealey.com/forums/view_topic.php?id=353&forum_id=2&highlight=turbo You didn't really want to know all of this stuff, did you? Kurt Last edited on 03-30-2007 06:58 pm by Jensen Healey |
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| Posted: 04-01-2007 12:18 am |
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54th Post |
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DeDub Member
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Yes, I do indeed have early regrinds: 907E0351Y, but ground till there's about .378 lift, which makes them appear to be Dave Bean regrinds. They're in fine shape; no visible wear. BUT reading that short PhD thesis (at least it looks like it with MY level of understanding) leaves me a bit concerned, as my cams are definitely JH, but the pulleys that were attached have a raised "LOTUS" in between two of the 6 holes in the web. But there's no sign of paint dots and yet there are 110 & 115 marked in the web with corresponding little slash marks on the rim. From my reading, the word 'lotus' on the web makes them sound like incorrect lotus pulleys but the other markings make them sound like JH pulleys. Yes, I'm confused. Another point is to use two solid web magnesium looking pulleys that were on one of my motors, which are also marked 110 & 115 but no other markings. Anyone willing to chime in with some advice before I button it up? I am deeply appreciative of the generosity this Club already. It's hard to imagine getting a dead JH running without this help. Thanks, David
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| Posted: 04-01-2007 12:44 am |
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55th Post |
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Jensen Healey Super Moderator
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You have the correct pulleys. The 110/ 115 pulleys were never used on Lotus cars.
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| Posted: 04-01-2007 03:44 am |
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56th Post |
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Greg Fletcher Administrator
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Jensen Healey wrote:The true Lotus 107 cams have the keyways offset so don't mix and match JH parts with them until you have done your research. I don't think that's correct. I have an original 107 cam and an original Federal C cam side by side and those are both keyed identically. You would need adjustable pulleys to make any difference on those.
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| Posted: 04-02-2007 03:40 pm |
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57th Post |
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Jensen Healey Super Moderator
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Hi Greg, I went to the garage to inspect several cams after your post. I was unable to see any offset when comparing the Lotus 107 to a JH regrind. The article in question states a 7 1/2^ offset which translates to 3 3/4^ on the cam pulley. This is about 100th of 360^ and I visualized an analog clock where this would be 36 seconds of movement on the minute hand. Not a easily detectable amount without accurate measuring tools. I may take the cams to the machine shop later this week to have these things measured and put this issue to bed. Kurt
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| Posted: 04-02-2007 04:02 pm |
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58th Post |
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Greg Fletcher Administrator
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I was eye balling it with a metal straight edge, not super accurate I know, but I was trying to see any minute difference. The tops of the lobes and the oil holes all seem to line up with the key ways. A large degree wheel would answer this question, I'll see if I can find one.
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| Posted: 04-03-2007 03:41 am |
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59th Post |
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Jensen Healey Super Moderator
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I tried the same thing and the straight edge seemed to line up off center on the keyway with both cams.
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| Posted: 04-14-2007 03:17 pm |
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60th Post |
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Jensen Healey Super Moderator
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After a clarification by a member of a Lotus forum, I do believe there must be a slight keyway shift from the old JH cam and the later JH and Lotus cams. How else could the later pulleys achieve a 10 degree change in timing when flipped over vs the 5 degree change of the older JH pulleys? I would still recommend avoiding mixing early and late cams and pulleys. Kurt
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