Van

I took apart the head on the ChumpCar motor... and I was surprised to find little shim washers under the valve springs. Or, more specifically, I was surprised to find *inconsistencies* with those shims - 3 of the intake valves had two shims while the last valve had 1 shim... And 3 of the exhaust valves had 1 shim, except one, which had 2 shims.

I just looked in PET, and I see that the shims are #14 and come in 2 different sizes... When I found 2 of them, there is a fat and a thin one. Were these used to compensate for variations in spring force?

Van

Other fun things I discovered... (mostly corrosion):

team44

i have seen shims in 924 buckets befor to get the right amount lift when using a race cam, as for the corrosion its normal for a motor that is 20 years old, and depends on the coolant or water used in the engine, and you do get condensation from short hops and not geting the oil hot, ( probibly befor it was a race car)

badcoupe

The shims are used to get the correct installed height for the springs they make up for inconsistencies in the various machining processes.

Van

It has never been a race car (yet) - it's been a junk car for the last decade...


I have to disagree with you here. The shims are under the springs - but the spring height will be determined by length of the valve shaft and the location of the keeper grooves. Further evidenced by the fact that the engine has hydraulic lifters - to take up any space inconsistencies between camshaft and the tops of valves.

The only thing these shims would do is put more preload on the valve springs - and it seems to me that 0.5mm of extra pre-load isn't much at all...

Will Feather

I knew it was only a matter of time before you dug into the motor...

blown 944

The different shims are to take up variance of valve depth to retain the proper spring pressure.

It sounds excessive to have 3 shims.

I personally have added a .060 shim to bump spring pressure. However, I measured to make sure there was no coil bind.

badcoupe

sid is correct the valve springs have a installed height spec, all valvesprings do. you use a special micrometer to measure distance from spring pocket to the bottom of the retainer. you then add shims to get the correct distance.

Van

Ahh, gotcha. I understand now.

Here's another question: is the little tang of metal in the oil pump supposed to look like that? Or is this one broken? I've done a google image search, but I can't find that specific view.

blown 944

I'd be going off memory, but I think you're missing a piece. I think I remember seeing a small corner piece missing but not that much.

Will Feather

Van I got a spare oil pump at my shop I could take a look at tonight possibly, if no body clarifies before then.

jem60

Oil pump is correct. I've got three apart now and all are identicle to yours.