mmadden55

Blew up my 355 and I am going with a Dart SHP 400 4.125 bore 3.75 stroke on 350 mains. I have several options on pistons. So the question is.. Is 11.4 to 1 too much compression for premium pump gas and or should I go down to 10.5 to 1 ? Anybody have any experience with this?

csmith3

Is this a daily driver, or a weekend warrior? Too bad you don't have Sunoco stations in TX. They carry Sunoco 94 and there is no methanol in it. Stuff's great man! You could always dump in a can of outlaw octane booster every tankful.

skinny z

The amount of static compression ratio you can run largely depends on the cam you select. Long duration cams require a higher SCR so as to maintain adequate cylinder pressure. Consider to the volume of the combustion chamber when selecting pistons. Conventional thinking says that a smaller chamber combined with a flat top piston will yield better results overall than a large chamber that requires a domed piston to achieve the desired compression ratio.
11.4:1 may be more than enough in some application or not enough in others.
Of course there are other factors as mentioned by the previous poster.

mmadden55

I'm running a TPI MAF Siamesed runners. Haven't picked a cam for this motor yet will be fairly long duration high lift cam, this is a weekend warrior street car. And yeah we got 10 % ethanol in the gas here too, smog city.

F-body-fan

I would agree with skinny Z. If you run a fairly agressive cam with a lot of overlap,
The dynamic compression starts to drop off & a higher static numnber is ok. If you are going to stay tame, you might need to stay closer to 9.5? Depends on how efficient the cylinder heads are too.

mmadden55

I have Trick Flow Twisted Flow aluminum heads.