FormulaZR

iTrader: (7)

After some discussion in another thread, it looks like the cause of my lost horsepower is partially due to my intake manifold (Fast 90). So, I'm looking for a new manifold.

Here's the application. It's a 383 LS1 in a jet boat. Power below 4500 rpm doesn't matter. When the boat launches, the jet acts kind of like a torque converter in that it flashes up to 5500 or so rpm and stays there. Cruising is the only time rpm falls, and I do not cruise below 3k rpm (boat comes off plane).

Engine specs:
383 LS1
11:1 compression
MTI Heads - 310 cfm intake/225 cfm exhaust @ .600 w/ 2.055/1.6 valves
Bullet Cam - 238/244 @ .050, .603/.610 lift, 112 LSA Hyd Roller
Yella Terra Ultralight non-adj rockers
Long tube headers 1-7/8"

Power *should* be about 550 hp at 5800-6000 rpm (that's where I was with a Super Vic and 850 Demon before the EFI conv); with the Fast 90/90 combo it's about 500 hp at 5500 rpm.


The options right now are:
1) Edelbrock Super Vic for EFI
2) Holley Hi-Ram
3) Fast 102 LSXRT


There is also a centrifugal supercharger in the future for this boat...it's not certain, but a definite possibility.

Zmg00camaross

iTrader: (11)

My buddy's jet boat we have a Vic jr on his with a elbow and 102 mm throttle body and does fine with it. Reacts just like yours really, just can't rev past 4500. This is on a 5.3. I vote single plane

RezinTexas

I only have experience with the lsxrt, however it really woke up my 383 above 4k rmps. the heavy truck pulls really hard up to 6k shifting.