Reconditioning s/b heads

[Jim Callan]

I have a '71 350/270hp all stock except for these heads that I installed about 25 years ago. The heads are the "camel hump" - 3782461/E275(date code ?) with GM7 in center and 3782461/F43 and GM10 in center. What heads are these? I suspect they are pre '70 heads. I have them removed to get a valve job and my question is - should I have hardened exhaust seats installed ?

THanks

[Brian Monticello]

Re: Reconditioning s/b heads

These are the standard chevy small block perforamnce head used in the early and mid 60's. They are generally 62cc and 1.94/1.5 config. The SHP versions were 2.02/1.6 and had a slightly larger combusion chamber volume - but are rare.

F43 - june 4, 1963
E275 - may 27, 1965

The question you ask usually sparks a debate here. The general consensus is that it is not needed unless you are going to run your for high RPM for extended periods (i.e. boat motor). That being said, I installed hardened exhaust seats because I run the motor hard and wanted some extra insurance.

Brian

[Mike McKown]

You've probably answered your own question

You've been running them for 25 years on unleaded fuel. If your driving habits don't change over the next 25 years, it may be time for another valve job.

There is a certain amount of risk of the seats coming loose and at the very least are expensive. I personally wouldn't do this until the seats got pounded out where you couldn't reface them and then do the seat thing. At the rate you're going, that will take 50-75 years.

[Jim Callan]

Maybe ........ but

I've driven the car, maybe, a 1000 miles in the last 10 years. It has set in the garage partially disassembled for the last 8 years. I now have time to 'play' with it. The last valve job was done when I put the heads on in '73. I wouldn't drive it more than 2k a year and with the available unleaded gas I thought new seats would be a good idea.

Is there a way to check the seats ? The heads are off, and they 'look' OK.

BTW - does anyone know a good machine shop in the Atlanta area ??

Thanks

[Duke W.]

Re: Maybe ........ but

Do the heads have the original integral cast iron guides or have they been rebuilt? What kind of seals?

Measure guides and stems to determine guide cleranace. Inspect the head valve seats and valve seating surface with a strong magnifying glasss. Look for upset metal, which is indicative of pounding. Older seats and valves, espcecially on the exhaust will have little gray or black specs, which is burning, but this is normal as mileage accumulates and is okay as long as a burn mark does not go entirely across the surface on the same line, which could be a leak point.

If the guides and seating surfaces are okay, you can just give them a good lapping and reassemble the heads with new valve seals. The lapping should remove most of the burn marks, and if the lapping shows a nice even concentric seat, the valves are seating and sealing well.

Duke

[Tom H.]

Re: Maybe ........ but

I pounded the exhaust valves on the 487x heads on my 72. Some of them were a quater inch up from original. I did this in one year, driving about 9000 miles, but to be truthful, some of them were hard miles. I had new hardened seats put in a month ago, and everything is back to normal. It is one less thing you have to worry about. Tom

[Jim T.]

Re: Maybe ........ but

My original owner 68 327/350 began its life using only Amoco Premium for about the first 5-6 years. It is still running strong after all these years and 95K miles. Car has never been on the strip and I try to keep the RPM's up and not lug the engine. Based on my 68's performance I would not have hardened seats installed.