65-85 under.

[442OLDS]

Originally Posted by Billy Nees

Ya can put any of the B-O-P Racers on that list.
When is the last time a B-O-P Racer got a bigger cam or a change in the weight of the rotating assy.?

Unless it's a misprint,the B of the B-O-P racers have 10.5 compression pistons in 1971,1972,1973 on the engine blueprint specs.

I always thought the 1971 engines started the era of low compression pistons and unleaded fuel.But I might be wrong,as I was only 5 or 6 years old at the time.I know the O got low compression pistons.