Machine shop advice - 71 LT-1 rebuilding heads

[Clem Z.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

In April, 1988 I bought two service heads PN 464045 for our '72 LT-1. The listed applcation was for 1971-1979 LT-1 and L-82 engines. I recall a label on the boxes that each head was packaged in, and my strong recollection was that the label stated that the heads were manufactured with hardened seats to operate safely on low/no-lead fuel.

Larry

the induction hardened seats have a bluish color in the seat area.

[Joe L.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

In April, 1988 I bought two service heads PN 464045 for our '72 LT-1. The listed applcation was for 1971-1979 LT-1 and L-82 engines. I recall a label on the boxes that each head was packaged in, and my strong recollection was that the label stated that the heads were manufactured with hardened seats to operate safely on low/no-lead fuel.

Larry

Larry------

The GM #464045 cylinder heads use casting GM #462624. These heads are SERVICE-only as far as 1971-77 Corvettes are concerned. They were originally used on 1978 Corvettes and they do have induction hardened seats, unlike the original 1971-72 heads.

[Joe L.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

unleaded gasoline was not mandated till 1975 when cat convertors came out. 70 big block heads had induction hardened valve seats.

clem-----


I was not aware that any 1970 big blocks originally had induction hardened exhaust seats. Heads using induction hardening for the valve seats have a different seat configuration with a slightly raised area. 1970 big block heads did not have this configuration. However, with the introduction of the 3993820 head for 1971 the seats did have this configuration. I don't know if they were actually hardened, though.

[George C.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

Dan,
I just went through pretty much the same thing you are going through. "Read the post titled My 365 that isn't", there is a lot of controversy over the hardened valve sets, and there is the risk of breaking into the water jacket, as your shop told you. The short version of what I did was all new valves, and valve springs, retainers, keepers etc. He did a multi angle valve job, Installed hardened exhaust seats, and no cutting of the heads. I should have it back together by next weekend, and I'll post some results.
There are several articles referenced in my thread which are all excellent reading and very educational.
Good luck with your decisions,
George

[Larry M.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

Joe,

Thanks for that info.

Larry

[Dan H.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

George,
Thanks for sharing, I read through the post and its very informative.

I have a third shop that my fathers friend is going to recommend. I know the way I' leaning towards, just very hesitant to cut original parts until I know more. IT's crazy, I'm fighting the urge to pull the motor/trans and have them refreshed as well. Scope creep is very tempting..........

[William C.]

Re: Machine shop advice - 71 LT-1 rebuilding heads

Dan, before you get into "Mission Creep" If the engine is still together, I'd have a "Leak Down" test performed. That will give you a good indication of the condition of the rings etc. Might ease your fears and the impact on the wallet.