oem to Cobra long block lost PSI

[Bradley G]

So what do I need to do to make up for the lost compression going from stock 10:1 to 8.5:1 Cobra long block.
I don't have the car back yet, so I'm way ahead of myself here.
I don't have the budget for cams and such so this is more for discussion than for stuff I can actually afford to do.
I am using a 2.8" upper , stock Trilogy lower and the upgraded tensioner.

[Zack]

You don't need anything.
A Cobra Long block works much better with the eaton in so many ways.

You will not notice any difference, because what you 'may' lose with compression you will gain right back with increased timing.

[JohnE]

You will need a re-tune for the lower static compression. The engine is going to need and be able to take more timing everywhere. You may actually see more peak power on hot days. A little tip-in response will be less, but not dramatic with the right tune.

[Bradley G]

I thought the same thing but my tuner Lonnie Doll told me it was optional to re-tune.
He also said no problem driving it to his shop in Indy.

You will need a re-tune for the lower static compression. The engine is going to need and be able to take more timing everywhere. You may actually see more peak power on hot days. A little tip-in response will be less, but not dramatic with the right tune.

[JohnE]

First off, Lonnie is correct in that you don't need a tune change for a lower compression ratio engine. It will be perfectly safe. However, power will be slightly down though. If you want some of that power back, a tuning change has to be made to slightly increase certain areas of the commanded timing in the programming.



If the knock sensor is used and its programmed to advance timing, then the computer will automatically adjust. However the factory programming only removes timing for knock in the Marauder. And most tuners do not use the knock sensors with blowers. I doubt yours will automatically compensate.

[Bradley G]

Thanks John, I'm pretty sure you are correct about the knock sensors were not utilized in the Tune Lonnie did on my car.

First off, Lonnie is correct in that you don't need a tune change for a lower compression ratio engine. It will be perfectly safe. However, power will be slightly down though. If you want some of that power back, a tuning change has to be made to slightly increase certain areas of the commanded timing in the programming.



If the knock sensor is used and its programmed to advance timing, then the computer will automatically adjust. However the factory programming only removes timing for knock in the Marauder. And most tuners do not use the knock sensors with blowers. I doubt yours will automatically compensate.