Originally Posted by cris well
I'm thinking about buying an 84 C-10 SWB with a 383 and a turbo 350 trans and a 3.42 rear end.
He told me that he used flat tops and 64cc RHS Pro-Torker Vortec heads with 1.94's and 1.50's. He said the compression is 10.5 to 1 but that seems low to me with this combo.
I'm thinking it would be closer to 11 or 11.5 to 1 without knowing the deck height and overbore. It has an Isky flat hydraulic cam with 236 duration. I looked it up and it's an oval track cam with a range of about 3000-7000 rpms.
He said it runs on 92 octane pump gas.
My question is did he have to set the timing really low to avoid detonation therefore cutting the power way down?
those "magic dynamic compression calculators" aren't worth NEARLY as much as everyone gives them credit for. 11:1-ish in a heavy truck with a highway gear (assuming 28" or taller tires) is going to have problems running on pump gas. With some very good efi controls you can get away with it but I wouldn't want to risk it on a carbed engine with a mechanical dizzy. Knock it down to 10:1 and while you still need a good tune it is MUCH more doable.
And to think that extra point of compression and all of the headaches it brings is only worth about 12hp under perfect conditions...