carb cfm

[Grbmaverickmo]

What CFM carb would you guys recomend for my stock 69 390 Gt? I have a 600 Ebrock on it at the moment works OK but not wowin. Carbs I have to try a 650 Thunder Ebrock on the shelf also have a few holleys. I`m thinking the 780 vac I have or 650 double. As allways Thanks for the ideas

[bluef100fe]

Way back when the 650dp I had on my truck with the stockish 360 and a set of headers worked very well... I'd imagine it would work very well on a 390... Hard to go wrong with the 735/750/780 vacuum secondary carbs also... Try them all and let the engine/car decide what it wants....

[cjshaker]

My mildly built 390 in my F'250 Highboy (cam roughly the same as a GT 390) loved the Holley 750 VS that I put on it. It starts perfect, idles perfect and pulls to 5700 perfect. It was practically perfect straight out of the box. Perfect plug color in the nearly 20 years since.

[Lenz]

I intend to re-use my 750 VS 3310 Holley on my 445.  It worked perfectly on the "built" 390 It's replacing.  They're more or less self regulating, you can change springs to get the secondaries in sooner if you want.  Far as I can tell, mine's "right out of the box", never had to touch it.  I have a local place with a chassis dyno where I intend to take the '64 when done to sort it out.  It'll be interesting to see the numbers where the rubber hits the rollers.  We'll see if we need to fool with the Holley at the same time.

[mlcraven]

What do you mean exactly by "not wowin"? 

I have a 650 vaccuum sec Holley on the mildly built +.030 390 in the Cyclone and, while I've not put the car through its paces at a drag strip yet, up to 5K rpm on the street it seems to be all the carb the motor wants.

[bn69stang]

What altitude are you at , it makes a difference  I M O , im at 5500 ft and my 428 liked the edelbrock eps 800 more than the holly  750 vs , im changing cams , and heads and rear gears and going to a holly 850 dp . Like Barry says you can tune a big carb down to work , but its hard to tune a small carb big .. Bud

[Grbmaverickmo]

What I mean by not wowin is the car runs smooth and idles well just in the flat out pull its seems lacking above 3500. I put the 3.50s in the rear and recurved the dist its responsive enough. Maybe I`m expecting alot. Just seems there is somthing lacking I`ve never been a Edlbrock fan so I have to try my 650dbl or I have a 700dbl also. I have to keep in mind it is a stock rebuild. Thanks as allways Chris

[Ratbird]

Are you sure the secondaries are kicking in? My stock 390 with headers had the original Autolite 4100 (1.12 venturi's) did the same thing. I finally figured out that the secondaries weren't kicking in.
After a rebuild of the secondary diaphragm I could feel them and a fair improvement.

[cammerfe]

If it were me, I'd look for a 6708 Holley. It's a big 'n' little 650 DP. Very forgiving and easy on gas if you don't kick it all the time. It's my favorite Holley of all time for a mild street engine.

KS