i'm looking at getting a federal mogul rebuild kit from summit and they come with either 9.72 or i think 9.34 pistons. with iron heads will 9.72 be too high for premium pump gas?

i will be rebuilding my vette L98 and heard that they came with X rods, if these check out ok will they be able to hold up to 400-450hp? or am i better off to just get some forged ones while i have everything apart?

 

you already have forged rods if you want to step up o nthe rods consider the PM gm rods, you shound be ok on pump gas ,but you never know for sure till you try it.

 

I'm at 9.75:1 and havent had any problems even with 89 octane.....

 

Im running around 9.75 on 87 octane without a problem. Im at 3000 feet elevation so I think that helps.

 

A lot will depend on your cam, tuning, coolant temperature, RPM, valve size, and, elevation!

Less dense air allows you to get a little hugher static ratio without detonation. Hotter chambers will contribute to knock, lean mixture will cause knock as well, and the profile of the cam has a lot to do with actual compression and how much static compression ratio you can build. Even the piston and chamber design will allow more compression if done correctly to make a tight quench area.