Jr Stock piston rules
 

I was reading a 1968 NHRA rule book today.It said under the engine rules that you could use any replacement piston "as long as it doesn't increase the compression generally the same in appearance".So on the 1955 265 engine with the flat top piston could you use a piston that had valve reliefs like the 56 and 57 engines had?

Re: Jr Stock piston rules
 

Unfortunately you have to make the 55 style work ; I believe CP is the only option as they made the first set for Carl Libucha after he sent NHRA a stock one.

Re: Jr Stock piston rules
 

I would say yes. Probably wouldn't need them anyway, with the cams they had back then. Even if they did , they wouldn't work with the stock spring specs.

Re: Jr Stock piston rules
 

Lyn -
I saw the Weir Bros. '55 Chev station wagon go through a tear down in 1968 and those pistons did have valve reliefs. They passed.

Re: Jr Stock piston rules
 

According to some vintage GM Parts Books I have, the flat top replacement GM pistons were discontinued in mid 1957,and replaced by the 56 57 piston with the reliefs.