Roqetman

Where would I find build specs to upgrade my 350 Cutlass to near W-31 power, to get around 310 to 350 hp? Not concerned about all original parts. I'm thinking I would need, 9.5-10.5:1 pistons, 308 cam, larger valves - 2.0"I & 1.6"E, Performer intake. What brand/size CFM carb would be recommended? I want to stay with stock heads and exhaust manifolds. This is doable or is it cheaper/better to drop in refreshed early 455? This would be for street performance, cruising and cruising nights. Thanks for sharing your expertise! Roqetman

70sgeek

there won't really be any 1 specific recipe to achieve your goal - many combinations of cam, pistons, carb and ignition will get you there, all mostly dependent upon your tolerance for tuning and idle quality.


I researched many different components for my 350 build and ultimately went with cam and piston choices that almost nobody subscribing to my thread agreed with - in the end though I was happily rewarded with a pump-friendly performer easily hitting the 300+ hp mark, with smooth idle quality and a strong street performance power band from off-idle acceleration forward.


'72 350 basic mods - bored 030, SpeedPro L2320F flat-top pistons, Howards CL510011-12 cam kit, E-brock 2711 intake with a rebuilt '76 Olds Qjet 750cfm. Ignition is Pertronix Flame Thrower II. Stock 7a heads were fully rebuilt, slightly surfaced but not ported. Crank was cut .010 and polished. My compression is roughly 9.5


It does like a lot of initial timing (18 degrees) but no detonation or stumble anywhere in the motor.

olds 307 and 403

That cam is small for 9.5 to 1, very similar to the Performer cam. Don't run the W31 cam unless you want a rough idle and low vacuum. The Performer is a low profile manifold, the Performer RPM manifold is much taller. I added a 1" open spacer to add plenum volume on my Performer intake. I am putting in a 214/214 cam on a 110 lsa with 9 to 1. I had the 204/214 can with 9.5 to 1, not a good match.

Fun71

I agree that a 308 cam, Performer intake, and factory exhaust manifolds are the wrong combination.

Roqetman

Thanks for the info! I have Pertronics ignition installed, currently running Edelbrock carb but like the 750 Q-Jet idea. One Olds expert said a roller cam was the best way to get more power, any experience or recommendations on these? I'd like a lowpy idle but I still need enough vacuum for PB's. I'd like to be a good street performer with more punch! The stock 350/4bbl/dual exhaust is only rated at 180 hp, that's at least 120 hp below my target.

Fun71

The 350-4bbl dual exhaust version is actually rated 200 HP @ 4400 RPM and 300 Ft-Lbs @ 3200 RPM (SAE NET ratings). The same engine in 1971 was rated 260 HP (SAE GROSS rating). I know, still a lot less than you want. Basically you will need more compression and a more aggressive camshaft.

coppercutlass

This what my combo sounds like. Its not the 308 cam its a lunati voodoo cam. 10 to 1 compression I can share more details if you want.

Its fully streetable runs power brakes has 3.90 gears and a 2800 stall. really needs a 3400 stall. runs 12.40's with the car weighing in at 3450 with me in it.

ROCKETMAN269V

Hey, are those some "new" Centerlines I see on there?

coppercutlass

In the video I shared it had the weld wheels but the centerlines are on now and they look great with my old tire combo .

Roqetman

What carb are you running?

Roqetman

That's what I was thinking. More compression, mid range cam, bigger valves. '72's are low compression, 8.0:1. What was compression on '70 350?

Roqetman

Sounds Wicked!

coppercutlass

I'm running a 750 double pumper box stock. With just a flipped pink pump cam.

Fun71

The 1970 350-4bbl was rated as 10.25:1 compression but in reality was likely just under 10:1 due to manufacturing tolerances. Also, it was rated at 310 HP but that was not based in reality. The 1971 350-4bbl was rated at 260 HP using the same SAE GROSS system but how do you lose 50 HP with a drop of just under 2 points of compression? The two engines were essentially identical other than the sizes of the piston dishes.

I learned back in high school that my 1970 Cutlass 350-4bbl, dual exhaust, 2.56:1 rear car ran dead even with a friend's 1971 Cutlass 350-4bbl, dual exhaust, 2.56:1 rear car until the top end of first gear, where I started pulling ahead. No way there was a 50 HP difference between those two cars.

olds 307 and 403

The only thing the 10 compression 70 350 has over the 71-up is the ability to run a bigger cam if the motor is in good shape internally. But it would still need more stall and gear to be anything. The manual trans cars probably put out that 310 HP having a cam similar to the 307 Vin 9, just like the W31 didn't produce only 15 more HP, the actual rating was 360 HP.

Roqetman

Would like to know more about details. I'm more into cruising than racing but I do like a wicked idle and strong acceleration. It's got PB, ps, At, and AC.

coppercutlass

Its a 10 to 1 compression 350 .030 over with speed pro flat top pistons.
#6 heads with ferrea big valves. 2.07 in. 1.63 ex.
edelbrock rpm intake
Pro gear timing chain
PRW ford 1.6 full roller rocker arms
Lunati voodoo cam 522/539 lift 233/241 duration came @ .050 lift.

Its a pretty basic engine nothing fancy although i dont have PS. A/C , or water pump driven off the belt. Just the alt.

I dont know how big of a cam you can run with a/c but i have power brakes and it has not been an issue.

ROCKETMAN269V

[QUOTE=Fun71;1012708].....how do you lose 50 HP with a drop of just under 2 points of compression? The two engines were essentially identical other than the sizes of the piston dishes. QUOTE]

The '71 Q-jet was jetted much leaner for emissions; ran a higher thermostat (195 vs 180); had TCS, which didn't allow full advance unless you were in high gear.