390 questions

[71fordkid]

I have some questions about a 390 im putting in my truck. Heres some background on it. It was re built about 50k ago, has the factory cast iron 4bbl intake, unknown cam (P.O said it was an "RV" cam..?), headman headers, and stock everything else. The truck will be daily driven, and drag raced some weekends.

Here comes the questions.

I'm looking for a carb for it, and On a fairly un-educated guess, I've picked out a Holley 750 cfm with vacuum secondaries. The holley site gave me a formula of C.I.D times max rpm devided by 3456. so being generous with the RPM, 390x5000/3456=565 cfm. the factory autolite 4300 was a 600cfm carb. 750 cfm is a big jump from that. do you think thats too big of carb?

Also, according to your brain and butt dynos, how much power do you think that will put out? my book (George Reid's High performance Ford engine parts interchange) says factory HP/TQ numbers were, if i read it right, 315HP and 427 Ft-lbs.

Last one, how about milage? 3.23's in the rear end with a beefed up C6 behind the 390. I'm assuming that when your running 310-350 HP, milage will go down the pooper. It shouldnt be that bad as long as i stay out of the secondaries, right?

[FreakysFords]

The 750 is probably going to be something of a pig on your engine. I'm running larger displacement, GT/CJ cam with some port work and CJ sized valves. The engine is VERY happy with it's 600 cfm vacuum secondary Holley.

VERY hard to say without knowing more specifically what you have, but those numbers are certainly not outrageous.

Mileage is gonna stink. I'm getting fairly good mileage on mine for an FE, but it's manual trans. The Auto's gonna rob some of what little mileage the FE has to spare, but keeping out of the secondaries will indeed help. If this is a car engine, then you might end up like my setup. I don't really need much throttle to get the job done, and that helps.

Frank