Originally Posted by SPRAYED 01

Mls gm gaskets. Don't even think of anything else especially cometics. I would run either a t6 turbo or a very large ar housing with your cubes. I think you could run about 15 but it well choke up up top

Originally Posted by TGriz

Hey all,

currently Ive got a 383 (5.3 bored and stroked) thats sits at about 10.5:1 CR right now in its current N/A form.

5.3 block at .015 deck height
Mahle flat top pistons -4cc 3.905 bore
Eagle 4" stroke crank
Eagle rods with ARP bolts
243 heads (64cc combustion chamber)

I want to lower the compression of this motor by swapping heads to a 317 6.0L head in either CNC ported or stock form. At 72cc for the 317 heads that puts me at about a 9.65:1 CR depending on the head gasket. Do you have the turbo in hand? I'd liek to see some of the measurements if you have it.

Turbo is a Turbonetics 76mm .96AR

Question 1: What kind of PSI could I push through this set-up?

Question 2: What head gasket should I use? (LS9, 6.0 MLS, Cometic, etc?)

Thanks for any help guys!

Originally Posted by TGriz

Which MLS GM gasket should I use? (LS9, 6.0 MLS) Also doesn't it have to be a gasket for a 4" bore because of the 317 heads?

you really think my turbo is too small? The kit that I have now has a T4 flange on it.

thanks

Originally Posted by Phil99vette

To start, I would keep the compression where it is, make sure the deck and block are flat with a very good surface, make sure you run good fuel or alky injection when you intend on turning the wick up. Should run pretty good.

Originally Posted by Johnv

I have a 383 with a TC78, with the .96 hotside it would fall over by 5000rpm,
stepped up to a 1.32 ar hotside and makes power to the limiter now (6700)

Originally Posted by TGriz

Interesting... you are the first person to tell me that I don't need to change my CR. Whats the reasoning behind that?

I always run 92 octane in the truck. and what measurements did you want off the turbo? I have the turbo now, I'm just really new to turbos and I'm not sure what the important measurements are.



Will I be giving up any power down lower with a 1.32 AR? and would that require a downpipe modification?

Thanks guys!

Originally Posted by TGriz

Which MLS GM gasket should I use? (LS9, 6.0 MLS) Also doesn't it have to be a gasket for a 4" bore because of the 317 heads?