01LS6SS

I just had an LS6 built, New LS6 block, rebuilt LS6 heads and a new LS6 cam. Everything is in the car and running but the car has slowed down from the previous LS1 with LS6 heads and cam. Went from 12.5s to about 13.0 which is basically stock LS1 speed. Everything else seems normal, runs fine. So confused.

subeone

iTrader: (5)

crank relearn has nothing to do with that.

Exidous

iTrader: (11)

You make no mention of a tune. The LS6 has more compression, better flowing heads, bigger cam and a better intake. Any one of those would necessitate a tune change.

01LS6SS

The car previously had STOCK tune on an LS1 with LS6 heads and cam and ran a best of 12.41

1FastBrick

iTrader: (16)

Any time you change the sensor or rebuild/ replace an engine you should preform a crank relearn.

That how ever is not causing the issue of running slower. Your old tune needs to be revised for your new combo.

What cam specs did you have before and what cam specs do you have now?

01LS6SS

1FastBrick, read the post again. The only thing different from the 1st motor and the new motor is the LS6 Block, everything else is Exactly the same. I did NOT do a crank relearn and its running about .5 and 3 mph slower in the 1/4 mile. I'm wondering if the computer is trying to adjust my timing based on the original crank and sensor tolerances. I've read that the relucter wheel can be off just a mm and can affect timing.
Thanks for any input.

subeone

iTrader: (5)

Get a retune. Idk what else to tell u

pdxmotorhead

Cam timing was degreed via lobe timing ?
Validated alignment of crank timing sprocket?
Main bearing clearance for cam and crank correct?
Head gasket thickness and bore clearance?
Intake gaskets?