No valve stem seals?

[SuperNovaSS]

I recently bought a set of big block rect. port heads. They were fresh and when looking them over I could not see valve stem seals through the valve springs. I pulled one spring and sure enough there was no seal. The contact the guy I bought the heads from and he said he would ask his engine builder about it. Today he wrote this back to me:


"Before you tear the heads down, check with an engine builder you trust. I am told it was not an oversight, but that on high horsepower engines, race cars, dirt track etc... they do not run the seals. This reportedly prevents the valve from burning at high rpm's."

Is there any truth to this? It does not sounds right to me. I could see running loose seals to prevent guide wear but that is about it.

Thanks,


Jason http://www.yenko.net/ubbthreads/images/graemlins/beers.gif

[VintageMusclecar]

Assuming these are a set of OE type heads destined for street use, leaving out the seals is a bad idea. Some shops will omit the seals just on the exhaust side since it doesn't see much vacuum, but given the proper clearances (dependent on valve and guide materials being used), there is absolutely no reason not to install them during a street rebuild. Leaving them out is all but guaranteeing excessive oil consumption, not to mention plenty of exhaust smoke.

As far as dedicated "racing" heads, while some may not see anything wrong with leaving the seals out, they aren't taking into account that excessive oil contamination in the chambers drastically increases the probability of detonation.

My $.02: have a set of seals installed.

[SuperNovaSS]

That is what I thought. I think it is a shop covering there butts for forgetting. The heads are a set of stock, unported 1970 291 heads. There is no reason not to run stem seals. I have a set of teflon seals on the way.


Jason

[sean70ss]

You always want to run the seals. You will end up having an engine that will smoke becuase of the oil bypass in the valve guide.

Sean

[Salvatore]

http://www.yenko.net/ubbthreads/images/graemlins/biggthumpup.gif Absolutely!