So I ran the numbers on my carb for my 400 that has a edlebrock 4 barrel intake. It's a 390 cfm. Which could explain why I'm having trouble with truck feeling starved for power. What size should I replace it with.? Or do I need to replace it? It's a holly four barrel. 77f150 4x4 400

 

Other than the intake swap what other changes have been made .. Is the compression ratio stock? A 650 cfm carb should be plenty something like the edelbrock 1406 .. What holly do you have (mdl number)?

 

I have ran 600 cfm on 400s and I personally thought they were a little big for a stock format. If they have headers and good exhaust, that helps, a straight up timing should help, improved ignition helps too. I have had trouble tuning the edelbrock to run well on a stock 400, they always seem rich. Now I think if you go to a 500 edelbrock or a 525 carter that might be a really good combo, I always wanted to try it. A 390 is probably the threshhold for performance, but I think a 600-650 is almost too much. I have ran a lot of 460s with 600 4 barrels, and they run nicely.

Remember that a bigger carb will hurt the off idle performance and eat more gas, but might give more high end. A smaller carb will help low end but kill top end. A properly sized carb will have good low end, and rev plenty for a streetable truck.

 

It's a 8007. 0562. It's basically stock.

 

It does have headers

 

If you are planning on changes down the road different cam etc.you'll want a carb that will accommodate those changes but still the carb can be set up for current conditions .. I think edelbrock is the best choice for the weekend mechanic to be able to do that .. Keep in mind there is probably not going to be an out of the box solution for you

 

What rpm should the 400 max out at?

 

This article will pretty much tell all you need to know on the 400 motor 351M/400 Performance Build Up

 

You must have a light truck as the f350s came with a 500 cfm 2 bbl. You can use the 500 if you change headers but you need to really clean it good and give the venturis a good polish if you straighten the timing. Old wives tail, If you use tooth paste you can polish metal, it works, you need to be old country to know how to do it. A 600 will do you fine if your keeping your motor relatively tame.

 

We just installed a Holley 470 truck avenger on my brothers 400 in his 1977 F250. Just got it going today. Runs great so far. Will report back one we put some more miles on it. His has headers on it.

 

well guys, installed a holley 600cfm. adjusted the timing. and this thing will run like a banshee. i dont know what the previous owner did to the engine but itll chirp the tires in second gear.its like a whole different truck from when i had the other carb on. i mean i can punch it at 50 and itll get your attention. thoroughly impressed. now i need to change the fluids in everything and fix the wiring and itll be ready for me to drive all summer long.