1931 Chrysler adjusting valves in 8cyl engine

[Gunsmoke]

I have head, pan and most attachments off my '31 Chrysler CD8 engine as I check it out. Everything generally looks good. I refaced the valves (some very minor grinding) and lapped them in their respective seats. Instructions for "checking valve timing" (page 53 in operators booklet) ask for valve tappets to be first set at .011 for intake valves and .012 for exhaust while engine is cold. It goes on to say "This clearance is necessary when checking the valve timing but should be changed to .007 (exhaust) and .005 (intake) when the engine is warm and as soon as the checking is completed because the latter is the proper setting for quiet valve operation. Since I have not done any work to cam or crank/pistons etc, timing of engine has not been altered, so valve timing should not change. So my question is what tappet clearances should I use cold before I reassemble head/pan/manifolds etc and not have to necessarily reset valves a second time? Starting and warming up these engines means replacing head, side-pans, manifolds, etc. Would setting at .009 and .007 be a cold target and depending on level of quiet, fine tune after engine has been started and warmed up? What has worked?

[vintchry]

Harold, Suggested clearances for an engine that has not been used of .010 and .009 would be my recommendation. This is not the last time you are going to be in there even if all is well the first time around. I take a length of masking tape and put it on the side of the head, then I mark I or E for each valve and the gap I am using on the first one of each. That way you are not guessing midway thru of which is which. In a previous email you mentioned using some old valves over, which is fine and lapped as you have. Did I read correctly you were going to use some Intake in Exhaust locations? I hope not as Exh valves have a different material construction than Intakes, and Intakes will burn quickly in an Exhaust position. Enough to run and check on this engine but not to leave in place. Good luck on this and i hope I have not confused you . Rob

[keithb7]

I read recently that these engines do not run with even temperatures across all the valves. This is why the final adjustment is best done when the engine is hot. I must admit that doing exactly that with my flat head has produced a wonderfully smooth, quiet running engine. 

[Gunsmoke]

Thanks Rob et al. The issue raised in regard to re-use of very good  intake valves in exhaust ports is new to me. Makes sense that exhaust valves would be more amenable to hot gasses. I have 16 used correct exhaust valves (most are thin on edges and not great candidates for re-facing)), and 16 used intake valves, 4 of which appear to be NORS and clean as a whistle, and 6 of which were very good for re-facing. Of course I have no way of knowing if the 4 NORS valves are of one type of material or another (I know they are NORS as they do not have a slot in top of valve). I also note the exhaust valves generally have a slight reduction in diameter in top inch of stem, while intake valves are uniform thru out length. Do the current manufacturers use different steel (or tempering method) for exhaust and intake valves of same size? I will plan to use the best of what I have to re-assemble the engine, gapping them at .010 and .009 for now. If engine runs fine, decent compression etc, I'll be pulling it out of the chassis for final restoration of chassis, engine etc, and will resolve exhaust valve issue later. May simply buy a set of new exhaust valves.