steveiguess

My buddy got a 400 small block for free, and im considering purchasing it. What all can you do to one of these bad boys? im running a zz4 350 now, but i was wondering what all of you have done with 400's. i have money, and im looking for some serious hp from this beast. i wana limit it to around 5k tho. tell me what you think, your results, and anything else you want to say.
thanks

RB83L69

HP = torque x RPM /5252

Torque at any given RPM is a function of CID, compression ratio, and cylinder fill. The more inches, the more compression, or the more full you can fill the cylinders, the more torque you can get. In a practical sense though, about all you can hope for out of a streetable 400, is around 550 ft-lbs of torque at its peak torque RPM; and probably 450-475 ft-lbs at the RPM where it makes peak HP.

You're not going to get "serious HP" if the RPMs are held to 5k. As you can see looking at the numbers above, you're going to be limited to around 425-450 HP if you design for a peak HP RPM of 5k.... which is not at all serious HP out of a 400. It's very wimpy in fact.

It's easy however to get 550 HP in a streetable configuration out of a 400. It will need to spin nearer to 6500 to do that though, as you can clearly see by the numbers.

The main thing to making a 400 work, is FLOW. Think BIG. Big heads, big cam, big carb, big exhaust. Especially heads and exhaust. Things in those areas that are "too big" for a 350, are barely enough or even too small for a 400. Go look at a big block sometime, look at flow numbers and such, and realize that a 400 is in that league.... not the same as some a little bitty motor like a 350.

What do you mean by "money"? How much are you willing to spend on this? And, what would you consider "serious HP"? i.e., let's balance goal vs budget. And also, what has been done to the car to hook up real power?

five7kid

iTrader: (14)

I think he meant limiting it to $5k.

Correct?

steveiguess

I have alot done to the car, built 700R4 tranny with a stall goin in soon, shift kit, fully adj. suspension, lca's, true duals, sfc's, full eaton rear end with 3.73's, etc. the car is built, but at the chance to do another motor swap ive gotta jump.

RB83L69

OK...

Look for some heads in the 200cc runner range at least, up to 215 (Dart Pro1 215s for example); and a solid roller cam in the neighborhood of 240-250° @ .050". With aluminum heads and a cam of that size, you'd want the compression in the high 10s, like 10.8-11:1. Zero-decked block, 72cc chambers, .039" head gasket, single-eyebrow (4cc) flat-top pistons, would be perfect. A Performer RPM intake would be about maxed out but would probably be OK; or you could step up to a single-plane. 800-850 CFM carb. 1¾" headers, minimum. 3600 stall 9" converter.

tommyt

How streetable would it need to be ?

Parrydise7

iTrader: (1)

You'd better take some of that $5,000 and have that block checked before you start throwing some serious money at it.