The Stovebolt Site Forums The Shop Area Engine Shop 4 barrel offenhauser intake

I would like to know the pros and cons on using a holley 390 vs. an edelbrock 500. This is on a otherwise stock 1965 292 cu., stock cam. I am using an offenhauser intake and plan on using aftermarket cast iron headers.

i personally went with the edelbrock on my 292, because it was a little cheaper. i heard both will work well, but may be a little overcarbed for a stock engine. heard the edelbrock had somethin' below or above somthin' so less prone to somethin'. sorry, i can't remember the specifics. surly a carb guru will chime in. i am a little more familar with the stock carbs than these aftermarkets.

I used a 350 on my Offy along with Langdon's cast iron headers. I turned my carb with the float bowl toward the valve cover. Hooked up my linkage with a bell crank. Manual choke hooked up nicely to. Ran my fuel line around the back of the motor. I used a heat plate too from Langdon's.
The 2 barrel carbs are flow tested different than 4 barrels. General rule of thumb is 1 1/2 times 2 barrel cfm equals actual flow. So a 350 acts like a 500 cfm 4 barrel. Mine works awesomely on my 65 230. I could dig up some pics if you like.

Backwards.
A 350 2 bbl. flows less than 350 when rated at 1.5" Hg.
To correct, multiply by .7071 (1 ÷ (3.0/1.5)^.5), in this case 247 CFM.

I am assuming either the holley or edelbrock would work reasonably well. I am concerned if there might be a difference in gas mileage and if the power valves on the holley are a concern.

Power valves are always a concern unless the carb doesn't have them.
Metering rods and vacuum pistons are a concern on Edelbrock, Carter, Rochester, etc.
The gas mileage will probably be slightly better with the Holley because the primary is smaller - but this assumes both are adjusted equally well. Out of the box, who knows?
I'm slightly more comfortable with Holley, and that's what I would base a choice on - are you familiar with or have spares for either one?

I ran 1 Carter 9400s (400 CFM) on a slightly larger 6 in my shop van for more than 400,000 miles with no issues. Power was MUCH improved over the single barrel; and so was economy. Win, Win.

Jon.

Thanks for the comments. I'll try to purchase a holley 390. I had a holley on my other 65 chevy (small block). The secondaries hung up on the gasket that came with it and I had to turn the key off. Big back fire. I still have a "fine tuning holley" book.
I'd love to have a Carter 9400 like Carbking has but they are very hard to come by.
Thanks again.