my question is if im going from a dished piston from an lq4 to a flat top piston like on the ls2 or lq9... would it get me better mpg.. i figured the flat top would need less fuel to get just as much power as a dished piston??? the reason i ask is because im goin to flat tops to get a little more bottom end grunt so i could lock my converter up earlier so i would get a little better mileage around town.... in the end the main reason im doing the swap is for more power and to make my 230 cam not feel so sluggish on the bottom end....

OPINIONS APPRECIATED

o yea... how much hp do you think you would gain going to flat tops over i think it -2cc dished

 

The LQ9 is a flat top piston, no? So bump in CR will improve bottom end torque. Don't know if it will make much of a difference on milage though.

 

i currently have an lq4 so when i say swap i mean to the lq9 pistons...

and yes i kno the lq9 is a flat top

 

What are the specs on your heads?

 

stock l92s i think 70cc

 

I think you would be wasting your time to be tearing the whole motor down just to be putting factory slugs back in the hole. IMO.

 

the bump in compression is worth it for the bottom end grunt which will improve mileage. how much is questionable. but it is true to tear it down to put back stock pistons isnt worth the trouble. put forged pistons in while your there in case u wanna push it harder

 

x2 my thoughts exactly

 

2nd that. If the motor is worn out, go for it. Otherwise you could consider milling the L92's down but it would take a pretty drastic cut. Assuming the LQ94 has about -2cc pistons to hit 10.01, then the the LQ4 must have apr. -7cc pistons to reach 9.50:1 compression. You would have to mill the L92's down to 65cc to get the 10:1. That's probably an easy .040-.045" cut so you could run into problems with the intake manifold lining up correctly (and you might need shorter pushrods).

Are you running a stall with that cam? That may be your best best to help the soft bottom end.

If you really feel the bottom end is too soft with that cam, change the cam. Pull it, sell it and get a cam that meets your need. You can throw a lot of money at trying to correct a bad cam choice.

Rick

 

my whole block has arp bolts and my engine only has 10k on it so it wouldnt cost more than a weekend to do the swap