[gman26]

I'm wondering if I should re-do the seats on my 69 350. The head shop recommends this because of the unleaded fuel. Are there additives I can use
instead?
Also, I noticed the Pontiac heads don't have valve stem seals like Fords. How does this work?
The valves and seats are in very good condition. So I'm just thinking about lapping the valves and
reassembling.

 

[Verdoro 68]

If you aren't planning on driving the car hard, you'll probably be fine without the hardened seats. I ran my '68 for years with the original heads on 93 unleaded and didn't have any problems with burned valves. If you are going install new valves I'd go ahead and have the hardened seats installed. There are additives out there (I used to use one called CD-2) but I don't really know how well they work. As a whole, I'm pretty skeptical of fuel additives.

I'm not sure what you mean by "Pontiac heads don't have valve stem seals like Fords." Do you mean they appear differently or are installed differently? Pontiacs definitely do have valve stem seals. I'm not familiar with Fords so I can't say how they compare functionally.

If you haven't already, I'd recommend buying a copy of Jim Hand's book "How to Build High Performance Pontiac V8s" while you are rebuilding your engine. Lots of good info in there, well worth the $20. There's also tons of good info and knowledgeable folks over on the performanceyears.com boards. The boards over there are geared towards older Pontiacs so you'll get answers to your questions a lot faster. I've learned a lot from those guys over the years.

 

[lars]

Testing done by GM and the SAE shows that there is no need to use the hardened valve seats unless you use the vehicle for extended periods at WOT (wide open throttle) such as when doing trailer pulling up the Rocky Mountains, etc. For normal driving and short WOT bursts, the exhaust gas temperature does not stay elevated long enough to cause any exhaust seat errosion. In fact, there are so many people doing poor seat installation, that the installed hardened seats tend to cause more problems than they solve (when they come loose and fall out...). So unless you're using your GTO to pull a horse trailer, skip the hardened seats.

Pontiac has valve stem seals on both intake and exhaust valves, just like all other GM products. That's why there are two grooves in the stems of all the valves.

 

[gman26]

Thanks for the info.
I thought the seals were the umbrella type.

 

[lars]

The umbrella seals are aftermarket and were not used by GM.