VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 cylinder head 1931

The cylinder head of my 1930 Chevrolet has water leaks. I have a cylinder head from a 1931 engine that I would like to restore to replace the other. I'm interested in any advice you might have for doing this.
My first question is: if the valve guides are replaced, is it better to use bronze or cast iron ?

Thank you for your help.

Hello Edmond,
From what I've read, the bronze valve guides are used in performance applications (racing and such). They also have to be of the correct formula/type of bronze. The cast iron valve guides are what OEMs use for longevity in their stock engines.

Thank you Harrys

The valve stems are a little bit worn, what can I do ? Replace them ?

The best cure for worn valve stems is replacement valves. Even if you install undersized guides you will have problems getting a good fit over the full range of travel. The valve stems do not wear uniformly.

It does depend upon how much they are worn. You might be able to use them if you are not overly concerned with burning a little bit of oil and a slight drop in performance if the wear is very slight and there are no visible ridges or steps on the stem.

Thank you for your answer Rusty.
Do you think that it is possible to slightly reduce the diameter of the valve stems to make them perfectly cylindrical with a metal lathe and then install undersized guides ?

might be able to, not sure how much material you would need to remove, to get into the integrity and risk bending them. but it may be same cost to just replace the valves. when i had my head redone, they made 2 new valves and put in all new guides. machined it flat, and cleaned it up. in know on the 1929 exhaust and intake are all the same size :) 1930 on exhaust and intake are different diameters.
if you only need a few can check out The Filling Station and Gary Wallace, sometime they have individual or complete sets. do a cost comparison. ask local head shops.

Hello Edmond,
Doing an online look for discussion of valve stem and valve guide clearance, I read this article:
https://www.streetmusclemag.com/tec...-check-for-valve-guide-and-seat-quality/
This may help you in evaluating your valve situation before committing to buy anything. I do not know if there are factory specs listed for valve guide clearances ( intake and exhaust ) for the 1931 Chevy head. I have not searched for that. If there is no particular listing, I believe that there are 'rule of thumb' clearance specs for different diameter valve stems to be found online.

Exhaust valve stem to guide clearance 0.002 - 0.004". Intake clearance is 0.0005 - 0.0025". You need new guides and valves plus the two reamers to cut the guides once they are installed.

Hello Edmond,

I had thought about the possibility of turning the valve stem and using undersize guides. The key there is finding reamers to give you the correct final guide size. I expect that you should be able to find guides that have enough wall thickness so the bore is undersize.

Now it is my turn to ask a crazy question. Are the valves heat treated (maybe case hardened for surface wear) in these old engines?

Hello cabboy and Rusty 37 Master,
Cabboy is correct as this is the same information in the ( Chevrolet Repair Manual - Independence Model - Series AE-LT - March 1st, 1931. Page 13
I did a google search asking: How are engine valves made to withstand heat? The response was:
Valves are mostly made from hardened steel, or more exotic materials such as titanium in high performance engines. ... Heat also makes its way up the stem and through the valve guides into the head. Some performance valve stems are filled with sodium, which melts and sloshes around inside the stem to improve heat transfer. So Rusty, I'd guess hardened steel.

Hello all and thank you for yours comments,
I eventually found valves from a “New Old Stock GM part in near mint unused condition.” They should come in about one month. Next question will be if the valve guides have to be replaced.

I recommend replacing the valve guides. They will be worn and could affect your new valves.

As Cabboy suggested, replace the guides with the valves. The guides are about the cheapest item of a head job and a very important part. Just make sure whom ever reams them, does them large enough and not too tight. You don’t want a valve to stick once the exhaust valves heat up.

I agree that the valve guides should be replaced and properly sized.