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Discussion Starter · #1 ·
Hello folks, I'm new to the forums, but I've gotten a ton of great info from this site. I've got a '72 Barth motor home with a 402 big block. I've rebuilt the original Quadrajet and it runs great. I'm concerned about the valve seats, because this was built in the old leaded fuel days. So I'm thinking of replacing the cylinder heads. I just picked up a set of cylinder heads from an '86-'90 pickup truck.

They were in good running condition when removed, and I need some advice as to what I should do to get them ready to go. I'm thinking clean them up, install some viton valve seals, and run them with some fel-pro head gaskets.

What would you guys do?
 

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Have shop install hardened seats and good to go
 

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I am not an expert on what heads came on motor homes in the early 70's or what heads came on truck engines in the 1990's. That said, I recommend that you check the casting numbers on both the heads that are on your motor home's 402 and the heads you are replacing them with. The numbers would be found under the valve cover, cast into the surface of the head. They would usually be 7 digits, and larger than date codes.

The reason you would do this is to compare combustion chamber size, intake port size and other features that could drastically change the performance of your engine if you replaced say "oval port" heads with "peanut port" heads.

Is your engine running good now...good compression, no oil in the water or water in the oil...no missing or excessive valve clatter? If the engine is running well, my recommendation is to leave it alone. If it has some of these symptoms, pull the heads and rebuild them, rather than replace them.

Good luck.
 

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I have never had a valve recess on old leaded heads. NEVER!
Do not let the engine run under preignition.. in other words do not let it ping keep enough octane in it or enough advance out of it to not let that happen.

I built a 1969 396 for my friends truck. Running 11+ compression and 215 psi cranking pressure.. It was originally in his 3/4 ton and used it to pull his tractor or haul stuff on his trailer.

many years later it still runs perfect.
My old double humps never had a seat go bad.. and this was 70,000 miles a year I drove them pulling boats and trailers using unleaded fuel.

Keep it tuned and you will not have any issues.

You let it rattle on low octane fuel or too much timing it will beat the seats out of the head.

I have seen more newer heads like 1980 and up with sunken seats than the old 1969 and older stuff.
probably the 210 f operating temps and low octane un-tuned deals beating them to death.

That is my experience. I used to drive 70,000 miles a year as did the wife.. and many old school deals with heads from 1960's.
We are down to 35,000 miles a year each now.
That is a lot of miles to do a lot of testing.
 

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Discussion Starter · #5 ·
Thanks Jeff Swisher. Maybe what I'll do is keep the newer heads as spares and just run what I've got. I do worry about the soft valve seats in there, but your post makes me feel better about running the old heads. I'll keep an eye on detonation.

What symptoms will I see if the valve seats start to go?
 

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Best advice I can give is to find someone else to remove the old heads and install whatever you chose.
I still have screaming nightmares from the only motor home I messed with a big block in. I finally decided that the factory suspended the 454 on a chain hoist and built the rest of the motor home around it.
 
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