The Stovebolt Site Forums The Shop Area Engine Shop Burnt valves!!

hey fellers,

Some of you may remeber a topic I posted about 3 or 4 weeks ago concerning sputtering over 45 mph. Well we did some research and found out it was most likely a blown head gasket.So he were are today I got the new head gasket right here beside me. we got the head off to go get it checked for cracks and get it cleaned up and found out the head gasket wasnt blown(still not in good shape though) but instead three exhaust valves were cracked!!So my question is is it alright to use the "good" valves out of my spare engine? If so what kind of prep work would need to be done?

Thanks,Slade

For a couple hundred bucks, I would send it to a machine shop and have it gone through. Just my opinion,
Scott

machine shop fees will be well worth your money if you do no have a way to grind the seats and the valves.

While yer at it have the machine shop put in some hardened seats for the unleaded gas. I think I paid $300 total to have the head on my 261 gone through- valves, hardened seats, guides, seals, valve job, vat and flux.

Are there any issues with rebuilding only a top end and not a bottom end? I've heard this can cause problems.

tlorber: The instances where I've seen a top end rebuild (used to be called a "valve job") cause problems is when some sort of performance enhancements are used (heavier valve springs, longer ratio rockers, increasing compression ratio, etc.) without an accompanying refresh of a tired bottom end.

In general, it used to be pretty common to grind valves, knurl or replace valve guides and replace the head gasket without opening up the bottom of the motor. In my opinion, it's only when additional stress (higher compression, stiffer valve train components) is added to the motor that problems might occur.

hth,

I guess I'm a little different than the others. I don't see a problem with doing it yourself. Most parts stores have valve spring compressors you can borrow. Remove the old valves & springs (keep everything in order so you know how they go back), clean everything up good. I wire brushed all the carbon off as well as solvent cleaning. IF the "good" valves are the same as the damaged ones go ahead and use them. I bought a valve lapping set with two grades of compound (coarse & fine) & used my variable speed drill to power lap each valve to it's seat. Be careful there. Go a little at a time & don't burn anything up. Use a bore brush out of a gun cleaning kit to solvent clean the guides (I used Chemtool as the solvent). Put everything back together and you're good to go. I had NO problems doing the head on my 38 other than needing help to get that boat anchor off & back on. Good luck.

I am a do it your selfer as well, I wouldn't have a problem swapping valves from head to head. Do as Tiny suggested in the above post, its a easy fun job. Soak the head with some Castrol Super degreaser of something like that and head to the car wash. Clean as much as you can before tearing it apart. NAPA sells lapping compound for less than $5.00. By new seals if it has them and some .015" shims to tighten up the valve springs just a bit.

Someday down the road you can pull the whole engine for a rebuild, but for now, this will work just as well. Joe

If you are thinking about doing it yourself you might spend the 20 or $30 to have the head magnafluxed before you go to the trouble of doing the work on the valves, especially since you've got cracked valves.

If you hunt this site somewhere it'll say which valves are direct swap for the ones in your head, might be BBC or SBC.

Also, if you look on ebay for Chevy 235 you can get a set of NOS valves for fairly cheap.