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Valve Adjustment SNAFU  Rating:  Rating
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 Posted: 02-05-2006 03:31 pm
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Mitch Ware
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So 8k miles after I got 19670 on the road, and this winter seemed like a good time to check/adjust the valves. Pretty straight forward job it seemed. However, 3 of the clearances were so small that I couldn't even get my smallest feeler gauge in between the cam and the bucket. But I wrote down a zero for those three and the other 13 measurements that I got and proceeded on. When I took the cam towers off, lo and behold, gaskets instead of permatex! Whoever rebuilt the engine decided not to follow the manual regarding that little item. A quick call to Jim at DMS and he said to clean the gaskets off, put everything back together and re-measure to figure out what shims I need. *sigh* So, I did. However, this time, I couldn't get the feeler gauge into 13 of 16 valves. And since some of the shims are already the thinnest, .060", that Jim said should be used, I have to go back to using the paper gasket to get the thickness that I need.

Anyone run into this? Possible causes? The PO gave me a receipt for the rebuild on the engine from a machine shop in NH, but I have no idea how reputable they are. I know that the engine was never run after the rebuild, and looking at the complete lack of ware on the parts it certainly looks like there really is only 8k on the engine. All of the parts came from DMS, I have the receipts for them. Is it possible that the valve seats are sunk too far into the heads?

 

As an aside, when you take the cam towers off, plug all of the oil drain holes. It scared the crap outta me when I dropped the top front nut on the intake tower into the oil drain hole and it went down into the engine. I was able to retrieve it using a thin small magnet on a soft aluminum shaft. The darn thing must have been over 12" down in the engine.

Mitch Ware
1974 Jensen Healey JH5 #111119670
1971 Triumph TR6 #CC66950LO

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 Posted: 02-05-2006 06:17 pm
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Judson Manning
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Isn't this the most-fun JH subjet of them all????

First things first, if there is no valve clearance on 3 valves, chances are at least one of them is already burned and you'll never get compression back in that cylinder w/o at least a valve job. 

Just because you have receipts doesn't mean the installer knew what to do with them.  See what I found when a supposed 'reputable' shop did work on a 907:

http://jhppg.com/gallery/album08/no4main

The problem with the <.060" shims is due to the previous machinist not grinding the valves during the last valve-job.  My machinist sets them all to the same deck-height which usually requires .010"-.020" to come off each vavle. 

One other thing to look-out for is that those damn shims move, especially when you're trying to install them on a head that's still mounted to the engine.  Some STP or Moly Assy lube does wonders for keeping them in place.

If you are unsure about the work done, and if you think any of the valves could be burned, pull the head off and see for yourself.  $100 to inspect & lap some valves is cheap insurance.

If you can't find a decent shop to work with, I can get it done for you here and ship it back to you with the valves shimed to match your cams and cam towers.

BTW:   I had to buy one of those magnetic 'snakes' myself to fish out a nut that I had dropped.

Last edited on 02-05-2006 06:19 pm by Judson Manning

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 Posted: 02-06-2006 03:26 am
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Esprit2
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Mitch,
When the valves are ground & lapped,  a small amount of material is removed from the mating face.   As a result,  they end up moving a little deeper into the valve seat.   The whole valve moves up in the head,  pushing the shim and tappet up with it and closing the clearance between the tappet and cam.

If the shop had done a thorough valve job,  it would have measured the height of the end of the valve stems after being ground,  then ground an appropriate amount off the ends of the stems to maintain the correct stem height.   From what you describe,  it doesn't sound like they did that step.

The cam carrier gasket is about .010" thick.   Removing it lowers the cam carrier relative to the valve stems and the clearances get tighter.   On a factory original engine,  the valve shims are usually fat enough that removing the gasket is no problem.   But for you,  it sounds like the easiest solution would be to continue using the gasket and then have a few shims custom ground a little thinner.   A few thousandths thinner is no big deal,  but don't make any really thin shims.   Like less than .050"

Any general machine shop with a surface grinder can custom grind the shims for you.   Just figure out what you need,  bracket the list at least one size either way (+/-),  then have the whole batch of shims done at once.   One set-up charge at the machine shop will cost less than going back repeatedly everytime you decide a different shim thickness is required.

Ideally,  the valve stems should be shortened so shims mid-range in thickness can be used,  and the gasket removed.   Also counterbore the oil passages at the front of the cam carriers to take the small O-ring that you're supposed to use when the gasket is deleted.

Good luck,

Tim

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 Posted: 02-06-2006 03:59 am
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Jensen Healey
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Or just have your cams ground to the next "performance" grind! That will give you some extra room for the shims!

Kurt

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 Posted: 02-06-2006 10:49 am
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Esprit2
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Yeah,  or that too...   ;-)

Tim

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 Posted: 02-07-2006 12:42 am
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Judson Manning
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Yeah...let's not do it the 'right' way.

As Tim points out any machine shop CAN do it the 'right' way.  The problem is finding a machinist that WILL do it the 'right' way.   Here's a hint:  If your vavle shims vary >.005" from valve-to-valve, I can guarantee the machinist didn't put much thought into it.

At first I was a little angry when I had to order 6 of the exact thickness valve-shims.  However, once I watched my machinist do another head of mine, I really gained an appreciation for the art.  Problem is, I never told him what to do.

Let's not forget the lack of any clearance on 3 valves.....a lot of effort figuring out how to shim these valves is nothing compared to what a dropped valve will do.

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 Posted: 02-07-2006 02:15 am
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Mitch Ware
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IIRC, the 3 valves that I couldn't get a feeler gauge into had shims in the .071"-.077" range (I don't have my notes here in front of me atm). That should leave me enough room to play with thinner shims to try and get the correct gap.

Would a leak down test to see if the valves are sealing be in order for my next step? Or should I just go ahead and pull the head and visually inspect the valves?

I appreciate the input so far. I'm glad I started this in January so that hopefully I can be done with this before the warm weather gets here.

Mitch Ware
1974 Jensen Healey JH5 #111119670
1971 Triumph TR6 #CC66950LO

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 Posted: 02-07-2006 03:16 am
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Esprit2
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It wouldn't hurt if you have access to the equipment.   If the results indicate everything is tight,  the valves are probably okay.   However,  if the leak down results are not good,  then you can't automatically assume bad valves.

In order for compression and leak down tests to be valid,  the engine must be at full operating temperature  (normal running clearances).   If the engine isn't operational and you do the test cold,  then a good engine could show marginal results.

You didn't say how thin your thinnest feeler gauge is.   What are we obsessing over?

Tim

Last edited on 02-07-2006 03:41 am by Esprit2

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 Posted: 02-07-2006 05:53 am
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Jensen Healey
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Just to remind those who already know and inform the newer members, the shims from the 8 valve SAAB 900 up to 1987 IIRC are a perfect fit. They come in metric sizes and I have ordered them on the internet and purchased them from the local SAAB mechanic. They are a bit cheaper than the Lotus items.

 

Kurt

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 Posted: 02-07-2006 11:54 am
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Mitch Ware
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My thinnest feeler gauge is a go/nogo that is .004"-.006".

Mitch Ware
1974 JH-5 #111119670
1971 TR-6 #CC66950LO

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 Posted: 02-08-2006 01:16 am
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Esprit2
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Okay...  so we aren't necessarily talking about negative numbers.   With the cam lobe pointing straight up relative to the tappet,  is there clearance?   Is the tappet free to  move/ spin easily?   If so,  then things aren't so serious.   Not good,  but not dire either.

Tim

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 Posted: 02-08-2006 01:23 am
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Esprit2
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Lotus valve shims for Twin Cam and 9XX engines are the same.   And both are interchangeable with shims for the Triumph TR7 and older Jags (Moss, Victoria British, The Roadster Factory... etc),   Saab 99 (local Saab dealer),   Cosworth & Climax (vintage racing suppliers)  and the Hillman Imp (faux Climax FW_).

Lotus ............ .060"-.150"   in 0.001" steps... 0.061,  0.062,  0.063...
Saab 99 ........ .090"-.120"
Triumph TR-7   .070"-.120"  in 0.002" steps... 0.070,  0.072,  0.074...
also used on Cosworth,  Hilman Imp,  Jaguar vintage 6's (3.4,  3.8,  4.2)

Tim

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