Hi guys. I have a new (to me) 69 350 block with #8 heads. Before I noticed the #8s, I assumed that I should use high-test gas. But with the #8s, should I be using regular unleaded? Anything else I should be considering?
Thanks,

 

Regular gas should be fine. #8 heads have hardened valve seats.

 

How do you know it's a 69 block? The casting # on the timing case shelf is the same 68-76. Did it come with #8 heads? If so it's most likely a 73-76 block. 69 blocks sould have #5 heads.

 

Anything is possible with an engine you don't know its complete history.

If it runs fine on 87 with no detonation, no reason to run more expensive fuel. An Oldsmobile engine will let you know quickly if it doesn't like its diet.

If you get some pinging, take the plugs out, get a penlight and look down in the cylinders to get some idea what pistons are in this engine. Heads don't affect Olds CR as much as the piston dish.