I'm looking to purchase a 385 fastburner and was curious about putting a 142 or 144 supercharger, but how many lbs should i limit myself on a crate? I still want the engine to last, not be a one time pull.

 

I've never considered such a build, but it's not too far from what Edelbrock's doing with their supercharged crate 350. Those pistons are rated to 500 HP by GM, so that would be about 4 psi, in theory.
Tossing safe ratings aside, I'd have no fear to run 7 psi minimum. The crate cam is close enough to ideal, but I'd most definitely upgrade the springs, pushrods and rockers.
I'd definitely insist on 1.75" primaries, preferably long tube Hookers, fully ceramic coated, inside and out.
I'd start by trying about 6 degrees initial, with a lazy centrifugal curve up to about 33 degrees total, then a more aggressive vacuum advance curve off manifold vacuum, with a one-way check valve to protect the tiny can from boost.
If you need a diagram, I can do that.

 

I was just looking at toying around on the safe side... my buddy said 8lbs and i thought 5lbs were about the limit on a non-forged crate. But thanks for the heads up on the 7lbs. If you would inform me about the info your reporting to me, i'm still in the learning curve of everything and would like to know more. Also what are a good pair of headers to full exhaust for this engine w/ or w/o a supercharger. I'm very much fond of my flowmaster 80 series muffer currently. But for headers & y-pipe i'm lost...

 

If you need to keep the Cat(s), then SLP is the source for legal 1.75" shorty headers. If you're not concerned about that, then Hooker Super Competition headers are the best choice.
The Flowmaster 80 does sound good, I've used it myself under my own third gens. But it doesn't flow well enough to support 385 hp, let alone 550+
Depending on which mufflers you choose, a pair of 2.5" might support 550 HP.
Bassani makes a dual 2.5" kit for 4th gens, you could use those pipes. But the Bassani muffs won't flow enough. Dynomax Bullets are good, as are Hooker Maximum Flows and Borlas. If you like 'em loud, the Supertrapps will also work.
It'll be tomorrow evening before I can get to the diagram.
If this was my build, I'd also replace the timing set with a Cloyes Street Roller. Partly I'd use it to retard the cam 2 degrees. But partly because the stock set isn't trustworthy in a supercharged build. Edelbrock changes it when they use this exact same short block assembly under their supercharger kit. That's not why I'm suggesting it, I'm just using them to illustrate.

 

I was debating flowmaster or borla, but considering the flow rate as you say, i'd most likely go with borla. I'm not looking for a dual exhaust, i'm thinking either 2.5" or 3" collectors. I was told 2.5" should be enough.. is that true? Also yes i do need a cat. Where would be the best spot to put an electric cut-out as well?... Whats different about the rollers?

 

Hold up, is this for your '89 RS? If so, you can't go this route. You can use a supercharger under a TB, but there's no legal TB that'll support over 300 real HP in a draw-through situation like this. You'd need to go blow-through, like a ProCharger.
Now, for 500+ hp, a single 3" straight pipe alone won't flow enough, you have to go at least 2.5" dual. SLP offers their legal 1.75" shorties for the factory '89-'92 dual cat, and you need that.
If you want to Y it into a single, it'll have to be the Mufflex 3.5" system. But there are no 3.5" cats, so the Y will have to be after the dual 2.5" cats.

 

I'm going carb, the crate engine is emission friendly with my state as long as i have a cat. So adjusting the carb is fine. I'm going with a longblock crate and was thinking of a supercharger. Hmm i'm trying to still make clearance with the exhaust, why would 3" not be enough?

 

A single 3" will not flow enough to support 500 horses. It'll be acting poorly by 4500 rpm.

 

7-8 psi as it sets. but with arp head studs and mls head gaskets, a little head work it could take more boost.
500hp.. i took out my 10bolt with a 650hp sbc.. i am sure you could do it with 500hp. i would just get the motor and build the drivetrain. drive it and get use to it then go boost.

 

exactly what my plan was, it was a question in the air though i had. Are the only conversion best suited in our vehicles a t56 or are there 6 speeds we can swap? i'm currently running a 700r4

 

Why not have an engine shop assemble an engine built for boost? Costs should be close between the two, but the built engine would have lower compression, forged pistons, and a supercharger cam.

 

You don't need MLS or ARP or studs for just 8 psi. You're just adding another couple hundred dollars to the cost of your build, for no good reason.
No head work will increase the amount of boost it can take, because your limiting factor is the pistons. No need to even respond to these armchair heroes who think they know it all, but have never tried it.
The T56 is the easiest and cheapest 6-speed, but Richmond Gear does offer an alternative.

 

Caleb is on to something, why not go that route?

 

Well i was wanting to run the engine a while till i could have the tranny done, and then consider boosting it. If i got the engine done & built for a supercharger would there be the same exact warranty as for just the crate engine alone?

What would be the best factor for headers with maximizing my clearance for headers back? I'd like to keep the dual look from the flowmaster, even if i go borla. Also if i go 3.5" like you say, then if i did the 1 to 2 out, then i could go either 2.5" easily for duals [3.5" to 2.5"x2]

 

The shop built engine warranty might actually be better since they know you will be boosting it as opposed to a crate engine warranty that might not cover damage from supercharging. You'll have to look into both.

 

thanks for the heads up, i'll look into it. I just know i get 30% off from gm crate engine from the dealer, because of my father, so i thought of it as a better option.