judgement call on valves

[Chrisrich]

I'm within spec on all but the first cylinder:
intake: .004 (s/b .005 to .007)
exhaust: .003 (s/b .006 to .008) I have the earlier spec motor...

Should I take care of this, or is it close enough for rock & roll?

Chris

[john.p.clegg]

If I was you I'd whizz them out,get an angle grinder on the shims and take a few thou' off them.....(only joking about the angle grinder)...

John

[bill308]

Chris,

I'd get the clearances right before you rock-n-roll, especially the exhaust clearance. The exhaust valves need to be on the seat for a period of time to help dump heat and avoid burning the seat. I believe once the exhaust valve heats up there is a chance you will use up the 0.003 clearance and not have firm contact with the seat when this valve is not open.

A good machine shop should be able to grind a few 0.001's off the shim in a surface grinder or better yet replace this shim with a new one of the correct thickness.

Bill

[reb53]

Chris,

Not really close enough.
For such a small amount I wouldn't bother with sending them out.

Get a piece of glass and use some 600/1200 carborundum to take them down. Keep them turning so as not to get a taper and you'll be fine.
No doubt you'll now get plenty of advice not to do this but I guess "the proof of the pudding is in the eating" as I've been doing this for the last 30 years on the same motor without the slightest problem.

Don't take any notice of marked thicknesses on shims because they may well have been ground in the past. Also, take into account the indentation made by the valve stem in the shim. This can be a few thou deep.
It's all very well to replace heaps of shims if you have heaps on hand.
I never have had a big supply, and have never found it necessary.

If you note down all the clearances, measure all the actual shim thicknesses, (not the marked thicknesses), you'll rarely need to change more than a couple. 1 EX goes to 3 IN which in turn goes to 3 EX etc.
Don't think I've ever done more than three. Not always exact but within a thou or so.

Ralph.

[rgh0]

If you grind down a shim do it only on one side and put that side to the bucket. The shims have a thin hard outer layer and if you remove that by grinding down the valve stem rapidly punches an indentation in the shim leading to excessive valve clearances. The larger bucket bearing surface does not do this so keep the one side of the shim hard and the soft side to the bucket.

And yes you do need to get the clearances in the specification limit. I would use the later specifications in all motors these days as it is extremly unlikely you have the orginal valve material on which these early engine specs were based.

regards
Rohan

[Chrisrich]

Excellent point, Rohan.
Thanks for that tip.