Hello forum,
A mechanic thought that my Edelbrock 750cfm 4 barrel carb is too big and unnecessary, and that I would actually get more power with a smaller carb. (The engine is a 68-74 4 bolt block, has Vortec heads, high rise Edelbrock manifold, and long tube headers.) He also thinks that I need an electric fuel pump, that my mechanical is not strong enough. I didn't expect that my carb might be too big...? He said I would save gas and having less fuel but a more appropriate fuel amount would actually add power...
Thanks!!

 

Depends on the displacement and how the engine is built. In a mild 350 for street use the 750 may be a bit much; however, in a big inch engine or a small engine built for all out performance, the 750 may not flow enough. Simply put, you build an engine for a certain amount of HP, and then select a carb sized to feed it. Too much carb will cause bogging problems and poor low RPM performance. Too small a carb will starve the engine for air and cause a loss of power. Whatever size carb is used, the air/fuel mix must be correct and fuel delivery must be adequate for the expected power if you expect good performance.

 

As far as the fuel pump, I have a Holley mechanical feeding my dual quads, and it keeps up just fine.
An electric pump doubles your chances of something going wrong.

 

I have pretty much the same set up you have and I'm running a 600cfm with no problems. When I rebuild the mothr with a mild cam I will stay with the same carb. Your manual fuel pump should be fine. I have an electric pump and I want to put a regulator on it.

 

OK thanks everyone. Good information, very helpful.

 

I disagree with your mechanic. You need the 750 carb to take advantage of the high rise intake, vortec heads and long tube headers. If I was going to change anything, I would change to a dual plane intake. You would get better low speed torque and acceleration. You would also get better mileage. A Rochester quadrajet would also give you better mileage and similar top end fuel supply. A typical Rochester is 870 cfm. You definitely do not need an electric fuel pump with your set up. Waste of money.

 

I ran into the same discussion when I had my 355 in my 68 Camaro and I used a 750 cfm. People told me it was too big and it would kill my gas mileage. No it didn't, it worked great but then again, it was built for some slight performance.

Now I did have a 350 in a 72 Chevelle and that was basically a stock rebuild and the 600 cfm carb I had on that worked great.

Then you have my 396, if you use a formula, it tells me to use a 780 cfm, but when I contacted Pro Systems, they ended up building me a 850 cfm.

So in the end, it's all in how you have your motor built.