Go for it, then just sell it for what you feel it is worth when you are done and flip the cash over into the holley. In the end as long as you are happy with it, that is all that matters.

Joe

 

this whole thread fails

 

Why?..... like wildcobrar, my experience with my junk over the years, and the '85 with a B-303 and 750 cfm Holley customer I had to work on last week..... 650 cfm carb is not too big for a 302.

 

I agree Joel5.0. Did Ford not put a 780CFM double pump carb on a 1970 302 Mustang that had 290/300 HP? I mean I have an 850 Double Pump Holley on my 351 inch pump gas street car. Car works ok, maybe it has too much carb????? Oh and the most recent build I did for a street/strip car for one of my clients was speced out by Patrick@Pro Systems. 393 Windsor on pump gas with a 950HP Pro Systems carb in a street Mustang. Given Patrick is a very big Player in the Horse Power Game I am not going to question or Doubt him!


Joe

 

First of all you are talking apple and oranges. The 290HP 302 in 1970 was the BOSS 302. The HP rating was a joke and if you removed the factory rev limiter that engine would spin up past 8000 rpm. The carb wasn't a Holley 780 Double Pumper. It was a Holley 780 Vac Secondary. The Boss 302 with the rev limiter in place would put out a minimum of 350 hp. Unleashed the Boss 302 would jump up well past 400 hp. The 290hp rating was just to get past high insurance cost. Back in the muscle car days HP ratings were just something to help the buyers. An Example was the Chevy L-88 427. It was rated at 430hp. Actual hp was over 550hp.

You CAN over carb an engine. While performance may be acceptable with a larger carb and it can leave you room to grow IF that is what your intentions are it's a fact that a properly sized carb for your application will perform better across the entire rpm range . A larger carb may make a few more peak hp but you have to ask yourself how often is your car at wide open throttle. There is a a certain point to where a carb becomes so large that peak power and overall torque will suffer. Most mildly built 302's will perform to their peak with a 600 cfm vac secondary carb and give you the best OVERALL performance.

 

The Holley 4180 (B5ZE-9510-GA), the emissions based Holley in stock '83-'85 Mustangs, is rated at ~580 cfm. Mr. Carrol Shelby used a Holley 715 cfm carburetor in the GT350 289 CID setup... and during my first days with the gang, we would look for 428 SCJ Holley's (735 cfm) for our street 289/302 setups. A carburetor is a tunable A/F providing device, and those 715 and 735 carburetors really worked.

A carburetor is an intake restriction by design, that's the way they work..... but you have to make sure the engine is able to breath when required, and the carburetor capable of supplying that A/F as needed. A 650 or 750 cfm Holley, is not too big of a carburetor for a 302.

 

i had a 780holley on a h/c/i exhaust and other stuff on a 289.

 

I had a 780 Nascar Holley off a 406 Ford Galaxie (406 was a runner) on my 65 289 2+2 Mustang back in the 60's. It ran great, no issues. It was quicker with an 600 cfm. A bigger carb will run OK but a properly sized carb runs better. Every engine is differant and some will respond to more carb than others.