54 Corvette hardened valve seats

[Donald M.]

I mentioned on the Corvette Forum that I was sending my 235 cu in L6 to be rebuilt and have hardened valve seats installed. Almost immediately someone replied that I should NOT have this done; that I could destroy a rare set of cylinder heads; and, that hardened seats were not needed. Needless to say, that got my attention. While I would not act on the word of someone unknown to me without further investigation, this gives pause for concern.

Has anyone had experience with installing hardened seats on a 54 Corvette inline six?

1) Are hardened seats necessary?
2) Is there some inherent danger of damaging the heads while doing this work? I'm not talking about sloppy machine work. I'm asking about a built-in problem any machinist might encounter; even a Corvette expert.

I need the collective wisdom of NCRS wizards, please. (That's why I love this place. )

Don Moses
Bayview, TX

[Joe L.]

Re: 54 Corvette hardened valve seats

I mentioned on the Corvette Forum that I was sending my 235 cu in L6 to be rebuilt and have hardened valve seats installed. Almost immediately someone replied that I should NOT have this done; that I could destroy a rare set of cylinder heads; and, that hardened seats were not needed. Needless to say, that got my attention. While I would not act on the word of someone unknown to me without further investigation, this gives pause for concern.

Has anyone had experience with installing hardened seats on a 54 Corvette inline six?

1) Are hardened seats necessary?
2) Is there some inherent danger of damaging the heads while doing this work? I'm not talking about sloppy machine work. I'm asking about a built-in problem any machinist might encounter; even a Corvette expert.

I need the collective wisdom of NCRS wizards, please. (That's why I love this place. )

Don Moses
Bayview, TX

Don------


1) In my opinion, hardened valve seats are NOT necessary. Actually, when hardened seats are installed, it's usually limited to only the exhaust valve seats. However, even these are not necessary in most cases. About the only circumstance in which they would be advisable is if you were to operate the engine at high power levels for extended periods of time. I doubt that any 54 Corvette is EVER going to be used in any circumstance even approaching this. If you want some extra insurance to make you feel better, use a lead substitute in the gasoline. It's not really necessary but it can't hurt anything.

2) It is possible to cause a cylinder head to be rendered scrap in the process of installing hardened valve seats. I don't know how prevalent this is for 6 cylinder heads but it can happen for a variety of reasons not related to a "botched job".

The best plan is to install valve seat inserts when valve seat recession gets to the point that the head would be scrap without installing inserts. At that point, you've got nothing to lose. What are the chances you'll get to that point? In your application, probably zilch.

[Michael W.]

Re: 54 Corvette hardened valve seats

Hardened seats are required in engines that run at high RPM and heavy load for extended periods of time. No Corvette engine performs that kind of duty- one or more of the conditions is always missing.

[Donald M.]

Re: 54 Corvette hardened valve seats

Having read several threads on this subject the consensus is universal that unless the seats are shot there is no need to install hardened seats. I will instruct my builder to do a valve job and contact me if the seats need further work.

As always, thanks a bunch to all who helped including those who gave opinions in the other threads I read. What did we do before we could exchange ideas on the internet???

Don

[Joe L.]

Re: 54 Corvette hardened valve seats

Having read several threads on this subject the consensus is universal that unless the seats are shot there is no need to install hardened seats. I will instruct my builder to do a valve job and contact me if the seats need further work.

As always, thanks a bunch to all who helped including those who gave opinions in the other threads I read. What did we do before we could exchange ideas on the internet???

Don

Don------

He should assess the condition of the seats before he does a valve job. There's no point in doing a valve job if the seats are shot. In that case, you go straight to having hardened seats installed and a subsequent valve job. A good machinist should be able to tell by inspecting the seats as-is. By the way, many machinists that perform valve jobs will not guarantee that if hardened seats are ordered they can install them without ruining the head. Of course, as I mentioned, if the seats are shot as it is, there is no risk in having hardened seats installed except the risk that the machinist is going to change you for the work even if the head cannot be saved.

What did we do before we could exchange ideas on the internet? Simple. Made more mistakes.

[Eric E.]

Re: 54 Corvette hardened valve seats

Funny, I was having the vary same discussion with another NCRS member today. I was always under the assumption that hardened seats were a 100% accepted practice and within hours my point of view has completely changed. Thanks guys!

[Michael W.]

Re: 54 Corvette hardened valve seats

GM adopted the practice of hardening valve seats in 1970 or so across SBC and BBC engine lines to prepare for the introduction of unleaded fuel in coming years. It might have been presumed at the time that all engines would otherwise suffer valve seat recession, irrespective of installation or operation.

It has been found in intervening years that very few vehicles (trucks, tow vehicles, motorhomes, boats etc.) actually suffered problems. If GM did know this in advance, it was probably not cost effective to divide production into 'hardened' and 'not hardened' heads, so just did them all.

Like always, myths refuse to go away so there's still some that promote installing hardened seats.