400wagon

Hey everyone, first post -- wondering if my combo will work fine with a stock throttle body with the ultimate tbi mods, or if I should upgrade to a 454tbi (which I have in the garage)

Here's the combo:
350 chevy (early 70's block)
305 tbi heads (garage ported and polished, new valve springs)
summit 1103 cam
holley street avenger single plane intake manifold
stock 454 tbi adapter topped with 350 throttle body, 80lb injectors, afpr
mid length headers, 2 1/2" duals with x-pipe
this is in an 89 s10 pickup, 700r4 tranny, 7747 computer swap

already started tuning for the combo, and part throttle and idle so far are great, but I need to upgrade the fuel pump and start over with the tune (pressure drops at anything over idle, goes lean @ anything over 3/4 throttle)

Can anybody guess if this combo makes enough power that I need the 454 throttle body?

RBob

iTrader: (1)

Once the fuel delivery is squared away check the pressure drop through the TBI. That will tell you how much of a restriction it is. Do a key-on, engine-off. Read the MAP sensor value and write it down.

Now go out and run the engine to the shift point. Get the the MAP reading. The difference in readings is the pressure drop through the induction system (TBI, air cleaner, filter, and ducting (if any).

If the drop is excessive then the BBC TBI will reduce it.

As for the fuel pump, unless you are going to run more then 24 psi along with an external FPR, do not put in a 255 lph pump. A 190 lph pump will be more then enough.

RBob.

400wagon

thanks for the reply. I'm just planning on upgrading to a gm tpi pump.