Trying to ascertain what carb I should be running on SBC

[tommott77]

The worn out 600 CFM Holley is just not cutting it and I am in need of a new carb and am trying to figure out; A) what size carb I need? What kind of max RPM I should be running (this is a factor in terms of how many cfms my carb should be pushing)? C) What kind of power/power curve do you think I would be getting out of this thing? I am a complete novice to small block chevys and have not owned an American V8 with a carb since I was 16 years old and had a Mustang.

 

Here are the specs taken from the receipts and notes that came with the car.

 

- LT1 4 bolt 350 block (3970010)

- Trickflow G2 Aluminum heads. Compression is either 10:1 or 12.5:1.

- 350/350hp cam, hydraulic lifter

- Keith Black Pistons (again either 10 or 12.5:1 compress)

- 6" H beam race rods

- Polished Steel crank

- Edelbrock intake

- Headers

- Flowmaster

- Stock ignition

- (And again) currently Holley 600cfm w/ KN air filter

 

Brought it by a shop that does some work on old Chevys and the owner recommended a 700-750 dual feed. That seems a bit large to me, but again I'm a novice when it comes American V8s and Holleys. My experience lies with Euro cars and Weber carbs. I would love to, and the ultimate goal is to, put 4 pairs of dual barrel Webers on there IF I can come across a kit for less than what I paid for the car, haha! The car itself weighs around 2200lbs, and I want to say has a 373 rear end, so perhaps us Z owners may be able to get away with something a little more aggressive than the graphs/formulas suggest. The car will see mixed driving on the street, auto-xing, and some track days.

 

So....? Any suggestions on carbs,.....ballpark what I should rev this thing to (5000,5500,6000,6500), nallpark ideas on how ponies this thing may be turning (250hp, 300,hp, 350hp, 400hp)?

[jt1]

Sounds like a 650 or 700 4150 Holley would work good for you. More important than the size is the tune on the carb. None of them are going to be just right out of the box. Spending some time with a wideband O2 meter is the best thing you can do while getting the tune right.

 

jt

[roro4g63]

I agree with jt. I am running a 350sbc zz4 with a 670 demon Carb. My last dyno run shows my setup hitting a wall at 5100 rpm. Close to what I expected for a Jane plain crate motor.

 

I had to run smaller jet sizes out the box cuz she was pig rich everywhere. But my Carb has been more than enough for my setup.

[tommott77]

I agree with jt. I am running a 350sbc zz4 with a 670 demon Carb. My last dyno run shows my setup hitting a wall at 5100 rpm. Close to what I expected for a Jane plain crate motor.

 

I had to run smaller jet sizes out the box cuz she was pig rich everywhere. But my Carb has been more than enough for my setup.

 

Appreciate the responses. Going to pick up a used 750 double pumper tomorrow to give a try. We'll see how it goes.

 

Also found out that a buddy of mine supposedly has 4 Weber DCOEs laying around. There is a pretty good deal on Ebay for a SBC crossflow manifold at the present time ($275). If he does have them, and cuts me a deal, I could be piecing together a quad Weber setup in the next couple weeks.

[Pyro]

Use a holley 3310 with a regular RPM intake (with square flange carb, not RPM air gap).

 

http://www.summitracing.com/parts/HLY-65-3310/

[nullbound]

Use a holley 3310 with a regular RPM intake (with square flange carb, not RPM air gap).

 

http://www.summitracing.com/parts/HLY-65-3310/

 

This is a great suggestion.