olds 307 build

[rocketracer380]

307 .040 offset ground crank 3.500 sj scat 6" rods 330 heads 54cc 1.875 intake 1.562 ex cam is solid 523" 530" 239 242 @50 106 lsa a holley street dominator and 650 carb ign is hei its goin in an 87 cutlass with a th 350 and 3500 10" appr 3400# 4.56 gears hopin for 12 sec et's i know just build 350 i'd like to make 375/400 hp

[F-BIRD'88]

I think you'll find that the "3500 stall" converter will stall about 500 rpm LESS (3000 rpm) when its behind your 307 cid v8 VS if behind a 350 cid V8.. LESS engine torque = less max converter stall speed on launch.
You want to launch the car at or very near peak max torque output rpm. On a 307 cid hot rodded engine with single plane it is going to be 4000+++ rpm. (5000 rpm +/-)

4.56 gears good choice

[F-BIRD'88]

Are the cylinder heads ported?

[gmrocket]

307 .040 offset ground crank 3.500 sj scat 6" rods 330 heads 54cc 1.875 intake 1.562 ex cam is solid 523" 530" 239 242 @50 106 lsa a holley street dominator and 650 carb ign is hei its goin in an 87 cutlass with a th 350 and 3500 10" appr 3400# 4.56 gears hopin for 12 sec et's i know just build 350 i'd like to make 375/400 hp

You’ll need a true min 10:75 or better to get there.

What crank are you using?

You might be better off with the perf rpm,, the Holley SD has very short runners which will hurt TQ on it...and the runners are a bit to big for 324”

[mag2555]

Those heads stock peak in Intake flow at .500" lift with about 180 cfm@28".
This could produce 370 hp but you would need far more valve lift and like a 12 to 1 compression to get to 370 hp!

Your going to need more then 4.56 rear gears also, you need to looking into the 5 something gear area.

Your going to need good valve springs also as the motor will need to buzz clean to a good above 7000 at which time a stock HEI module is well on the down hill side of what it can for firing rate wise.

[Walter R. Malik]

I think you'll find that the "3500 stall" converter will stall about 500 rpm LESS (3000 rpm) when its behind your 307 cid v8 VS if behind a 350 cid V8.. LESS engine torque = less max converter stall speed on launch.

4.56 gears good choice

When buying a "Custom" torque converter the stall speed has usually been designed to be correct for whatever engine / power level is being used

[F-BIRD'88]

I think you'll find that the "3500 stall" converter will stall about 500 rpm LESS (3000 rpm) when its behind your 307 cid v8 VS if behind a 350 cid V8.. LESS engine torque = less max converter stall speed on launch.

4.56 gears good choice

When buying a "Custom" torque converter the stall speed has usually been designed to be correct for whatever engine / power level is being used

True true if you can tell the converter builder how much torque @what rpm.. A engine dyno test is best. Otherwise they have to estimate the engines torque curve to get the converter build dialed in to get the desired max stall speed on launch.. A off the shelf "10" 3500 stall converter" will stall about 400 to 500 rpm LESS IF when behind a 307-324 cid engine.. If this lil olds v8 is using a single plane intake getting the real stall speed right is critical on this.

[F-BIRD'88]

If you can port the heads and get the flow up to the 225 to 230 cfm (in) and 150cfm ++ ex even with the stock valve size you'll do pretty good. The stock zs cast flow is pretty modest.. you can fix that. Get the real compression ratio up to 10-10.50:1 for 92 octane gas .
The Performer RPM manifold is probabily a better choice.


Its a lot like hotrodding a 305 or 307 chevy.

[rocketracer380]

comp is 11:1

[F-BIRD'88]

comp is 11:1

Too high for pump gas.. If you plan on driving on pump gas bring cab fare.

[My427stang]

I agree with the above posts

1 - You are going to have to get it breathing deep. Port the intake and the heads, you may lose torque with the single plane, but can drive around it on the drag strip. Get the heads working well, and the intake slightly better. I think you will find that the early intakes also have a low carb pad that hurts the direction you are trying to make it traveel

2 - Not knowing the rest of the cam specs, I also think you are deep into race gas territory with that cam assuming a 106 ICL. If that's the plan, good to go, but if it's a street car, you'll have to make some adjustments

If I were attacking this one, I would get the heads flowing as good as I can (or go aftermarket if available) prep the intake to match the heads. Then cam for the RPM range you intend to run, and pick pistons to support the compression I needed. I'd also do my best to go a light piston and modern rings to sneak every bit of power out of it

[F-BIRD'88]

If the measurements and cr calc is accurate its not that hard to tame the cr a bit so it can run on pump gas .

The chamber rework will likely also aid breathing.

[rocketracer380]

not concerned with running pump gas

[gmrocket]

The chamber isn’t prone to detonation...your good with that comp and premium pump

I’ve made 440hp&tq at 10.5 comp with the 307 and over 500hp 450 TQ at 11.4 with better fuel.. all under 6500

Heads only needed to flow 220 and 230 with a 2” intake 1.5” ex

Don’t over size the primary pipes..1 1/2 to 1 5/8” is fine

[rocketracer380]

gm rocket anymore info on those 307 builds