4.3 twin turbo 1975 Chevy Monza

[moronmechanic]

Hey group, I'm new and I figured this would be the best place to go for advice. After seing the time-slip page, I KNEW I was in the right place! Hah!

I have dealt with small blocks for a long time, blowers, turbos, etc. I have never built up a twin turbo 4.3 yet, but the time is here.

I have a 1975 Monza that came from the factory with a small block, 4.3 V8; yes, special displacement just for the Monza. I built up a 327 at 11:1 and it hauled ass, a real V8 rollerskate. The car handled like a lawn dart though. I figure that installing a 4.3 would help in that department by removing some of the weight from in front of the front wheels.

I have an OMC cobra roller cam and some 10240209 heads ( 92-95) and I have a complete low-mile 1996 4.3 from a blazer or something. Here's the plan:

*Make custom intake and use Ford 2 barrel throttlebody from truck, keeping each plenum almost separate. Unless I can get a good deal on a ty/sy intake.
*MegaSquirt fuel injection, crane cams ignition.
*Home-built water-to-air intercooler setup to flow water or C02.
*twin T3s with .63ar and .60 compressors.
My questions:
Should I use the even-fire crank or go with the older odd fire? Can the stock crank hold up to the beating I plan on dealing it?

Go with the 96 heads or should I buy some GM bowtie heads?
How about valve size?
Best springs to use?
1.5 or 1.6 rockers?
I have some forged 18cc dished pistons, will my CR be ok with stock high compression heads? I want to see at least 20psi of boost. That's what I run in my 1987 Subaru! I'll be using AVgas at the track and 92 on the street.

Damn, this newbie is curious! Any help would be greatly appriciated!
-Chuck- Portland Oregon

 

[Tydriver]

Re: 4.3 twin turbo 1975 Chevy Monza

Stick with a different Intake.. The SyTy intake leads to uneven fueling (witnessed by plug inpection). Also this will have benefits for hood clearance and intake tube routing.

96+ Vortec heads and stock crank have run into the low 10s with mega boost and tuning.

Dunno about bigger valves, some peeps say go for it, some leave it alone.. Forced induction changes everything.

Oddfire vs Even fire.. What are ET goals ? Stock Even fire cranks have run low 10s. Oddfire is cool if you have an assload of $$ to blow and want a tuning nitemare, but it can turn the R's.

Stock SyTy compression ratio is at an unbearable 8.35:1. I'd shoot for 9:1 if possible, with decent heads knock shouldnt be an issue.

It all boils down to what you want to spend and what your ET goals are. Phil Long has gone a 10.2x with a good build (nothing exotic) in a 3700# AWD truck, others are all over the mid 10s with a similar build (nothing over the top so to speak).. I would think that the Monza would be better in terms of weight so expect gains there as well due to being LIGHTER.