sonic28

hey people i have twin 350 mags 1992 pushing out 245 hp at the motor not the drive. i would like to build it up to 300hp or better with out going to vortec i am running alphas which im up grading to bravo's can yo give me some good suggestions what i need i don't want to suck water back.im currently with gil exhaust 700cfm holly on the stock manifold.im running in salt water so ineed to stick with the stock maifold due to the bronze water jackets.the boat is 1992 sonic 28 my speed currently 60 mph on gps

BajaRunner

245hp 350 mags? are you sure there mags?

sonic28

yes prior to 1992 they called them 350 mags and when i purchased the boat i didn't even question? then spoke to mercury and 300hp started in 1993

traviss

i thought 350 mags back then were 270 hp.


You need to put those motors of yours in the corner and build yourself a set of strokers.. Plain and simple My 383 for this spring will be 570 + hp... Just takes good parts and 110 octane

220BR

Yeah, I think somethings screwy here. My '92 5.7L came with flat cam and lo-rise intake and Q-jet and supposedly generated 260 at engine, 230 at prop.

A '92 Mag used the exact same heads, but a hi-rise intake (cast iron z-28) and a roller cam and a rejetted Q-jet. It *supposedly* generated 300 at the engine and 270 at the prop.

Can you verify that you have a roller cam?

Agree with Traviss, I turned my 5.7L into a Scat 383, but kept the ponies down around 360 to pamper my Alpha.

traviss

i know My 270hp mag, didn't have a roller cam. it was flat tappet. but it was a 1989

Oh i have a alpha too.. Haven't broke it yet.. Ran one year with a 380 hp 383, this year it was about 510 hp and have never hurt my drive... For some reason it is staying together, this new setup will test it good

sonic28

i don,t have a roller cam

traviss

This is what i ran on my first 383 setup

-Vortec cast iron heads, machined for higher lift cam, screw in studs and guideplates

-Edelbrock air gap intake
-750 holley
-9.9:1
-222/230 .509/.528 roller cam
-EMI exhaust

I was between around 380 hp


If you look at the block it should be machined for roller cam.. All factory blocks from 1987 1/2 and up should be machined for it.. I have seen a few that have not been machined and I have a seen a few that have had only about 1/2 of the machining work done..

sonic28

did you ever have a problem with water being suvked back. or was your cam mild enough

traviss

Not yet.. even with my last 232/242 duration on a 112 lsa cam I haven't had a problem. A little help I have is my EMI risers don't dump water into the exhaust till about 18" down the pipe