VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc 31 valve part identification

I’ve looked through the manual and parts guide and can’t find what the black plastic caps are that were on the valves. We are in the process of having our 31 head fixed and these came off when disassembling. They were between the retainer and guide. What’s the purpose?

On some engines, we call these plastic caps.....umbrellas. The umbrellas ride on the valve stem and they keep the oil from sliding down the valve stem, which reduces the amount of oil which might end up in the combustion chamber.

Awesome, thanks! What’s thought on putting them back in as I put it back together?

They were an after market add on, and if your valve to guide clearance is correct (as it should be after reconditioning the head) you shouldn't need them.

Personally, I'd leave them off.

Old is correct. Unless the valve guides are worn you do not need those umbrella seals.

That design seal was used primarily on Ford’s starting in the 60’s. In the 40’s (I think that was when) Chevy added their version of a valve stem seal. It was a square cross section o-ring that fit in an additional groove machined into the valve stem.

Some people are concerned that the umbrella seal is too good. The concern is that it prevents any oil from getting to the valve stem and does not let just a little bit lubricate the valve stem moving in the guide.

I did add them to my ‘37 because it was burned quite a bit of oil past the valve guides. It reduced that oil consumption quite a bit.

If you are going to use them get new ones. They do get hard with heat and age. I have pulled valve covers and seen bits of broken seals lying on the head. If the seal gets hard it will not move up and down with the valve. So the valve stem makes a big hole in the umbrella. That totally negates their function

Thanks for the fast replies.

They are very nearly 1 size fits all and most engine reconditioners have lots of them on the shelf if your local parts supplier hasnt.
Tony

Hi Tony,

When I was looking for the seals to put on my '37 i found that there were at least 3 sizes: 5/16", 11/32'", & 3/8".

The 11/32" size fit my 216.

Chevrolet first used a valve stem seal and on the intakes only in `i941. From1942-1947 non all valves. The were metal caps on top of he valve stem caps. Often rwmovd as they added to vave stem noise.
In rhe dealership WE REFERED TO THEM AS RATTLE CAPS.
In 1948 a rubber O ring waas inserted between the valve stem and retaainer capand that ontinued fo many years.
The keeping oil from running down the valve stem stopped the cloud of smoke on start up and when backing off at high speed. They no increase valve guide wear and i USED A VERSION ON MY 1934 AND 1939.T
t
THEY ALSO PREVENTED EXCESSIVE CARBON FORMARION ON THE VALVE STEMS.