What size of carb does a 400 take?

[88 Fox GT]

I know this isn't really Mustang related, but I feel the classic forum is probably the best place to ask. A guy came up to me today and wants me to put a new carb on his truck with a 400 in it. I'm guessing it's a 400M, but he didn't say. He needs to know what size of carb to buy. He will probably get a Holley or Edelbrock. Thanks.

 

[jerry S]

I know this isn't really Mustang related, but I feel the classic forum is probably the best place to ask. A guy came up to me today and wants me to put a new carb on his truck with a 400 in it. I'm guessing it's a 400M, but he didn't say. He needs to know what size of carb to buy. He will probably get a Holley or Edelbrock. Thanks.

stick or auto? If an auto, what kind of stall? work horse or street perfomer?

 

[hotrodnut]

A good formula to use for carb size is: cu. in. times max RPM divided by 3456, example: 400cu. in. X 5000 max RPMs = 2000000 divided by 3456 = 578.7. So around a 600 cfm carb at max volumetric efficiency would be good if that is tha case with the max PRMs.

 

[bnickel]

i would say that you first need to find out if it still has the factory 2v intake or if he's already swapped it for an aftermarket piece. also find out if has done any other mods to the engine, IE cam, headers, etc. i think that about the only decent 400m intake would be the performer or a stealth if weiand makes one for the 400m. but if it's all basically stock and already has a 4v intake i'd go with a 600 e'brock or carter carb. if it still has the 2v intake and he doesn't want to buy a new intake and convert to a 4v unit then i'd go with a 390cfm holley 2v carb

 

[68 Coop]

I've heard tales of a 27hp increase with a Demon carb. If/when the Edel goes, that's the carb I'm trying next.

 

[88 Fox GT]

i would say that you first need to find out if it still has the factory 2v intake or if he's already swapped it for an aftermarket piece. also find out if has done any other mods to the engine, IE cam, headers, etc. i think that about the only decent 400m intake would be the performer or a stealth if weiand makes one for the 400m. but if it's all basically stock and already has a 4v intake i'd go with a 600 e'brock or carter carb. if it still has the 2v intake and he doesn't want to buy a new intake and convert to a 4v unit then i'd go with a 390cfm holley 2v carb

You're right, I need to find out if it's a 2v or 4v. The engine is stock and just basically needs a stock replacement because the stock carb took a crap.

 

[Edbert]

You should be able to buy a decent replacement 2V at the local parts house. Worst case is they'd have to order it, it should be cheap too.

We had a 400M in a 78 Bronco with a 2V on it. The engine seldom rev'ed above 3,250 but had enough torque to drive up some amazing hills. All I am saying is that for a truck or off-road application I'd leave the 2V on there, put the Demon on your Mustang.