i have a holley 600CFM carb with edelbrock intake. i was goin to put it on my 79 460 bored .10 over. it has a edelbrock plus cam and headers. many ppl have told me 750-800CFM. i thought i heard stock 4350 motorcraft carb was 450cfm or sumpin. i know i many not hit peak power with a 600, but it still should be streetable?

 

It will be streetable but it will be starving over about 4500. If you are not planning on getting on it any you can drive it with the 600. I would seriously consider a 750 cfm or larger. You can go to Holley.com and they have a calculator that will give you the optimum carb for your set up. I started out with a 650 and mine wouldnt hardly turn over 4500. Changed to an 850 Doble Pumper it came alive in the upper RPM range.

 

Yep, and it hurt gas mileage and beat up the bottom end torque. Double pumpers are race carbs and do not belong on street machines Expesially big heavy trucks (compared to muscle cars they are big and heavy) because of the mechanical secondaries. Unless you are turning 6000 rpms the 850 is too big.

 

I agree with you. The 850 worked great with my set up it is built for drag racing. Thats why I advised to go to Holley.com and use there calculator. It does a good job of specing out the right size carb for your application. I dont have the double pumper on it anymore. I currently run a tunnel ram with 2 600 cfm vac. sec. carbs which is definetly not for every application.

 

I just ran the calculator on Holley.com and specs for a mildly modified (headers and mild cam) with a top RPM of 5500 and vac. secondarys. It came up with a 750-770 CFM Vac. Secondary carb. I also ran it as bone stock with a max of 5000 rpm and it was between 650 and 750 cfm.

 

My bone stock 1984 carbed 460 will never see 5000 again. Mainly because it just abuses the engine and gains nothing. 4500 to 4600 is the max I will take it and a 600CFM works fine. It's an older list 1850 600 cfm vacuum secondary with power valve protector installed and the vacuum spring stepped up one from stock and staggered jetting. Just the swapping in of this carb for the 4180 boost my gas mileage almost 2 mpg and improved bottom end preformance. Recurving the dist. gave another mpg and exhaust added another. So I'm just over 10 mpg and that's with a 4.10 rearend. This same basic carb set up on my 1968 F-250 with 390 and C-6 and 3.73 rearend got 13 mpg. I learned a lot at the couple of Holley tech clinics I attend eons ago.

 

thanks for the great info. ill run this 600 for now. im lookin for bottom end grunt. 4500-5000 is about all the rpm i want, im goin for a nice street / cruzer set up. i have a older holley 750 with vac secondarys. im not sure if its a double pumper. it was run on a 350 chevy. its been sittin for a few yrs now, that one could prob use a complete rebuild. does anyone support runnin a 1'' spacer or so between the carb n intake?

 

If it has vacuum secondaries it is NOT a double pumper. DP's have mechanical secondaries.

 

simple and general rule of thumb. smallblock 650cfm,bigblock 750cfm

 

Interesting, but car manufactues and Holley don't think that way. Over carbing and camming are the to most done changes and hurt performance the most.