'83 valve shims

[lwasson]

Someone please explain this one. First, its been awhile since I've had time to work on the car or visit the forum but its good to get 20 years of lotus grime under my finger nails again. To refresh some of your memories. The car: 1983 Esprit Turbo and has been abused over her 20 years. So far a complete rebuild of suspension. The engine was taken out before work took me away for the summer. Just about all valve clearances were in spec but a few were out. Checked the shims and intakes were OK but the exhaust shims were way too thin. Range from 0.047 - 0.054inches. Shims in the parts manual only go down to 0.060". There is no evidence the shims have been ground or the valve stems. Discovered some more rigging someone had done but I fixed that and not part of my current problem. I have not taken the head off to check the valve seats and that will not explain the thin valve shims. I had not planned on a complete engine rebuild so I would like to leave the head on. This is not a fatal flaw so I can live with it and the valve clearances are within spec and the ones that are out are out but 0.001". Car has 43,000 miles.

My question: Why are the shims so thin? Where did these shims come from?

Thanks a bunch,
louis

[mikelr]

Are you measuring the shims in the center or towards the edges? Over time the centers can get pounded thinner by the valve stem.

Also, are your clearances that are out of spec to tight or to loose?

>> Edited by mikelr on Monday 20th October 06:26

[cnh1990]

In the USA you can get then from the usual sources. JAE if you live in the west RD if you live in east. We never really find the exact shim we need. Just about all of us get a glass plate, sand paper, and grind them down and check with a mic to get the exact thickness. When we redo engines we have a grinding party. A bunch of people with the same set up seated around in circle just shaving a tad off each shim for the required fit.
Calvin

[lwasson]

I contacted Don Tingle of Tingle's Lotus and Steve at SJ and they both said that something is very wrong to have shims that thin. Someone in the past has ground the valve stems, seats or both to get the correct valve clearance. What they should've done is replace the valves and seats. In its current state the geometry is off. The valve springs are not right allowing for possible 'slapping' of the valves, shortening the valve and seat life. All this to say the head has to come off and new valves and seats are to be ordered. Arrrrrgh!

[cnh1990]

Are the cams original?

[grk]

I wouldn't worry about the valve spring tension - I've found them to be well on top of the job - I've run these engines to over 8000rpm on standard springs so a 10-20 thou reduction in the seated pressure is unlikely to have you in any danger. The shims shouldn't be so thin because there is a danger they will split in two; however you can have 20 thou ground off the pad on the undersaide of the cam follower to get you back in the correct range - most machine shops should be able to do this.

It is a bit odd that the shims are in this range - the engine must have had a valve seat job, in which case it seems a shame to do it again.

GARRY

[lwasson]

Garry

The main problem is that there is no history on the car. There are numerous problems and rigging. Does it have different cams, a valve seat job....I can't tell you and neither can the previous owner.

I wanted a project car and boy did I get one!!

Thanks

[GRK]

It's pretty unlikely the cams have been changed - most people when changing cams fit a performance cam that is reprofiled - the process of reprofiling a cam involves the base circle of the lobe being reduced: this has the effect of increasing the size of the valve shims. If the valve shims are undersize it normally means the valve seats have been cut/ground; this sinks the valve in a little further and reduces the size of your shims.