dual quads on 390????

[gt5001967]

390 30 over 270h cam edelbrock heads, headers,now want 2x4 blue thunder intake, holley 1850 600cfm will be too larges? ,or 450s or maybe 390cfm,i'm really confused,please help me!!

[Barry_R]

You'll wrestle with the tuning a bit - - but the dual quads will work. I ran a set for a long time on a 390. The progressive linkage actually works nicely on the street. The 1850s can be problematic because they have a big PCV port in the base that sometimes wont seal well against some of the factory intakes - - not sure how they'll work on the B-T. Something to check.

[Carnut427]

Vacuum secondaries will only open as much as the engine will handle (when properly adjusted). Have a blast!

Dan

[Tony Aprile]

I have always liked multi carb setups, as I put dual quads with 600's on my 460. Vacuume secondaries are the way to go on the street, as Dan said they open only as much as the engine demands.

The 390 cfm will give the best throttle response but will suffer at high rpms, the 450's are mechanicals I believe ??? and if so I would use as my last choice. The 600's will not have the throttle respose of the 390's but will make up for it in the 3000+ rpms.

Tony

[Carnut427]

Holley made (makes?) a 450 vacuum secondary carb...original application was a '70s 390 if memory is correct.

Dan

[Tony Aprile]

Dan.... I stand corrected, I looked in the Holley catalog and see a 465 CFM universal vacuume FORD carb. I confused that carb with the 660 cfm mechanical 1:1.

Tony

[BOURRET]

Originally Posted by Carnut427

Holley made (makes?) a 450 vacuum secondary carb...original application was a '70s 390 if memory is correct.

Dan

I used those 450 with vacuum secondary and have been very happy with them on my previous 390. They are still in perfect condition and I even used them for 1 month on my new 482 engine before I got my two 600 cfm. I keep them as spare, they worked better (more reliable and better quality ) than the 600 cfm.
The price of the 450 was more than twice the price of the 600 cfm.