Pelican Parts Forums

static compression ratios mean very little, what matters is the dynamic compression ratio and this is considerably influenced by choice of cam.

What cam do you plan to run?

Dynamic compression MUST be in the range of 8.0:1 to 9.0:1 for that motor to generate any decent amount of torque. The single plug usually falls in 8.0:1 to 8.5:1 range while dual plugs are in the 8.5:1 to 9.0:1 range.

You can have a static compression of 12.0:1 and still only have 8.0:1 dynamic compression. You can not spec the static compression needs without concidering the cam at hand. Changing just the cams in these motors can easily move you from 7:0:1 to as high as 9.5:1 on dynamic compression!

Avoid the trap of assuming you can't run 12:0:1 static compression on 93 octane, or assuming that your 10.5:1 pistons are safe without knowing the cams, that's also a huge mistake!

Quote:

Originally Posted by panzerfaust (Post 9067016)

hi sal

stock usa or euros... hard to tell when the slugs are still in the car.

my first priority is reliable build spec not an all out track motor. prefer mahles, since they were a stock oem company but he shape isn’t correct for twin plug. JE is an option with nice flat tops but I hear folk are weary of the expansion capability of the alloy with the stock jugs that may cause piston slap or knock until warmed up. Any other alternatives for pistons?

Not looking for anything near 11:5CR since im being conservative with poor quality fuel in regions of the usa. No knock sensor, stock cams and stockish motronic (for now) I would like somewhere 10:1 or 10:3 CR. Down the road I may do cams and intake (MAF or ITB)

Ive been down the high CR roughly 10.5’s road before and had to reduce the advance and made the motor sluggish on the low end. the car did make A LOT more power up high though...

regards pf