F-Body Demon

iTrader: (1)

Hey guys. I stumbled onto some good luck over the past few days! I got a FREE GM 350ci 260hp Chevy Crate engine, with 8,000 miles on it! Met a guy who had a "305" that he didnt want anymore and said I could have it. Pulled the pan to check the bearings and look for chunks of crap, measured the skirt of one of the pistons and found out it was 3.998...AKA not a 305. Looked up the casting numbers and found out it was a 350, he still gave it to me though, good guy.

But moral of the story is I am building this puppy up and need some input from yalls. I want to make 325 hp and 375 tq without a head swap or even taking the heads off and keeping the power below 4k and redlining at 5.5k. I figure its in good working order as is, why mess with any of the hard stuff. I had planned the following...

Speedway Roller Tipped 1.6 rockers.
Summit .420I/.442E Camshaft + matched springs
Edelbrock Performer EPS manifold
Holley Vacuum Secondary 670 carb
Long Tube headers, smaller primary tube size 1.5-1.625. More TQ
MSD Blueprinted HEI

I didnt want to use power adders due to cost. And I have half this stuff anyways. Just wanted a torquey carb car that didnt spin to the moon.

Anyone think of anything else I can do to add some TQ? Maybe a electric fan and electric water pump? I can do that for sure....brain fart man haha. Ideas?

sofakingdom

iTrader: (1)

They may call that motor "260 HP"; but, part number for part number, it's THE IDENTICAL SAME THING as the 180 HP 350s of the late 70s. 8¼:1 compression, 993 heads, 929 cam.

All you're proposing to do that will significantly affect the HP as compared to how the factory got that "rating", is put in the "RV cam", and run a smaller carb and intake, and smaller diameter headers. That said however, that cam is a decent choice (if not exceptional or even particularly competitive) for a low-compression smogger 350. That's pretty much the application it was designed for back in the 60s.

You might get it from 260 HP to 275 HP using the same "rating" method GM used to turn what was a 180 HP motor in a car, into a 260 HP motor in a crate; but it won't run like "300 HP" in a car.

Expect 210-220 HP or thereabouts, in terms of how it will run against real-world, comparable power. That is, you (or GM) could call it a "300 HP" motor all day long; but it will put about 160-175 to the wheels, and run about even with a car with a 220 HP stock motor.

Sonix

iTrader: (1)

Yea, I think if you want some power you'll need heads Geez, at 8000' everything is pretty lethargic eh? I'd go HIGH compression. I know i've said that to YOU on this board before, if you can get away with it, give'r!

Shred

i got a goodwrench 350, with mild mods on it but i think its got more than 220hp. ive heard the rating was around 265hp, so with an air gap, hei, edelbrock carb, and headers i figure around 280hp, not sure about torque though. the problem now is the rest of the drivetrain handling further improvements

sofakingdom

iTrader: (1)

Shred, sounds to me like you're at least 20 HP DOWN FROM the "rating", right there alone.... the "rating" was created with a 750 Holley. Careful with your "improvements".

Sonix

iTrader: (1)

I also think it was rated with headers... And HEI. HEI isn't really some kind of high end upgrade, that's the norm. Air gap manifold might counter act that horrible edelbrock carb, but I think you're right back where you started - at best.

92droptopws6

iTrader: (10)

mod list
change those heads,vortec's work well for the money
the cam has to go!comp 280 has a nice powerband
a good set of RR 1.6s
performer rpm 1" 4hole spacer
t-350 trans,shift kit etc.
2800 11" stall w/3.42 gears
holley 750 vac.sec. 3310-2
msd 6al
zz4 GM dist.
i had one of these motors and this set up woke it up big time 81 camaro went from 16.5 to 13.8 with these mods