3100 L82 Pistons

[ItsVince725]

Are there flat top pistons that will fit a L82 3100 for a boost in compression? The shop where I'm taking auto tech classes has a disassembled L82 and it has dished pistons, so I assume that they all have dished pistons.

I could also safely assume that a change in pistons would require computer re-tuning?

[ericjon262]

Are there flat top pistons that will fit a L82 3100 for a boost in compression? The shop where I'm taking auto tech classes has a disassembled L82 and it has dished pistons, so I assume that they all have dished pistons.

I could also safely assume that a change in pistons would require computer re-tuning?

Don't know on the pistons, but the change in compression will need a tune.

[robertisaar]

CR calc says 9.55:1 with stockers.

with a piston dome/dish volume of 0(completely flat-top) and stock pin location, compression is calculated to be 15.65:1.....

yeah, i'd say it would need a retune. with that kind of compression ratio, i'm not sure if you could actually avoid pre-ignition due to just that much compression heating up the air/fuel mixture as it squeezes it without running some incredibly high octane fuel. i'm not sure how to calculate that kind of temperature rise though.

EDIT: if you have the pistons made so that the pins are significantly relocated to where you end up with .06" of deck clearance, you move to a more reasonable 11.81:1, but the quench is crap at that point.

[trotterlg]

If you put iron head pistons in an aluminum head engine you will end up at about 12 to one CR depending on the head gasket you use. Both have dishes in them, but the iron head pistons have about half the dish as the aluminum head pistons do. Larry

[robertisaar]

using otherwise stock 3100 specs with the iron-head 3.1 piston dome volume and piston deck clearance, comes up to 10.79:1 with a quench of .077.

[ItsVince725]

using otherwise stock 3100 specs with the iron-head 3.1 piston dome volume and piston deck clearance, comes up to 10.79:1 with a quench of .077.

That sounds pretty good. I didn't know the stock compression was so high with such deeply dished pistons though.

[3400-95-Modified]

The cylinder head has a very small CC.

[trotterlg]

I think the iron head pistons are about .100 deep and the aluminum head pistons are about .200 deep. It makes an easy path to more compression if you want to run a bigger cam using aluminum heads.