I am assisting a friend in building some big Torque and decent HP on his TBI motor.

A new well built 383 is going in... my questions, what do you all recommend for aftermarket top end parts... money is truly not an object, whatever it costs... it costs.

Would really like to get a solid 450 ftlbs of torque and even 500 if possible down in the 3000-4000 rpm area.

Which Throttle body ?
Which Manifold ?
Who's heads ?
Which cam profile, including specs ?

Headers will be going on too.

btw, in short, how difficult is it to convert TBI to TPI ? a 383 Superram motor is a possibility as well.

thanks for all your help, TBI is not my strength.

Todd

 

My dad just did a 383 TBI in a friend's 87 El Camino. It used a ZZ4 cam, ported Sportsman II heads, 1 3/4" headers, a stock ported TBI intake, and a 454 throttle body (intake bored 2"). He's spent several weeks making a custom chip for it, but its dialed in now. Even with a 700R4, a 2000 stall converter, and a 3.08 rear end, it hauls pretty well! Lots of tire frying torque. No dyno numbers or track time yet, but he wants to take it to the track soon.

To convert to TPI, you need the computer and prom, fuel pump, wire harness, and the TPI hardware, plenum/runners/base/tb/injectors. My dad can convert the wire harness, since you're local.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

As for the throttle body, your options are a little limited. You have three main choices. There is the holley 2BBL 670. Second, there is the big-block throttle body, made by Rochester, and is said to flow 650 cfm stock. Thirdly, there are a few 4BBL units available, one made by Holley, and another made by Affordable Fuel Injection. At least, I think that's the name of the company.
Each one has it's pro's and con's, but I'd look into getting a 4BBL as long as whatever product you are going with is flexible enough to be useful.
As for a manifold, you are able to use any manifold that will fit your heads. There are a few carb to TBI adapters out there, and fabbing one isn't too hard, either. Pick one that's going to complement the rev range. TBI doesn't need any radical manifold oddities to work well.
The heads are the same story. Pick a pair that'll work with the rest of the combination.
The cam you pick is going to have sufficient vacuum for the computer to be happy. Usually you'll need a LSA of 109* or more. Otherwise, pick one that compliments the combo without going too nutz on the duration.

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No guts, no glory.

 

Thanks for the input guys

This is for a 93 Silverado truck that does a lot of towing... they want not only a ton of torque down low, he also wants some decent HP at 5000-5500 rpm, which is hard to do with a TPI, unless you move to the Superram.

thanks again.
Todd

 

no. holley is the only one making 4bbl throttle boddies like ours. affordable fuel injection setups are holleys. there are lots of people making throttle boddies, but not tbi, with the injectors over the blades.

 

Hey! you got a truck too ... talk to me. I'm trying to do something similar, only mine's a 350. I've been getting a lot of conflicting info on what will work and what won't.
I've been making a lot of calls and i can't give you much help in the way of firsthand info, but i could tell you what i've heard.

keeping the ECM and the C.A.R.B. happy, both at the same time, puts limitations on things.