need advice on a sbc 400

[seasquirrel72]

Hi,

I have a 18' 72 sidewinder with a berkely 12jc (?) pump and A cut impellar. It had a 455 in it but I blew it up last summer. I'm putting in a Chevy 400 as a replacement because I can't afford a 454 right now. I will be using the boat mainly for cruising around, nothing hardcore. What kind of power loss/gain can I expect from a small block vs. big block? Would this impellar work with my motor, turning around 4,500 rpms and 320hp (rough estimate)? For people running small blocks in their boats, is there anything important I should pay attention to?

I plan on smoothing the bottom of my boat and painting it also. Is there any way to do this without flipping the boat over?

[455maveric]

400 SBC can make big power it's a great engine with the right parts how much power do you want in fact thats what i should be doing is ditching my 455 olds for the 400SBC due to so many go fast parts fo cheap.

[concord 1]

400 SBC can make big power it's a great engine with the right parts how much power do you want in fact thats what i should be doing is ditching my 455 olds for the 400SBC due to so many go fast parts fo cheap.

i agree!!! sbc 400 can be one hell of a engine!!! cam carburation and intake and head work,maybe even a 434in
stroker kit!!!!!

[Darkside's Calling]

I was thinking of building a 433 (400 .030 over with the 4" stroker crank. They have rods out now that clear, or almost clear without grinding. I ran som tests on Desk TOp Dyno, and was looking at 625-650 HP NA, and around 850 with 7-9 lbs boost... the problem is the 2 bolt block....

[boatermike]

seasquirrel, how fast was you with the 455 and what rpm?

[seasquirrel72]

I believe i had it around 5k at 65mph max and cruised around 45mph. This is just going to be a stock rebuild, nothing fancy. It is a 4 bolt main, .030 over, running stock heads so there's plenty of room for improvement once i save up some more money.

[boatermike]

well my experience with cars tells me the 400 sbc has more juice than a 455 olds but thats just redneck seat of the pants dyno

[RLP]

I would 4 sure go with the 350 rod 5.7 in the sb 400.
The 400 rods is the weak link in that engine.
So you will have to get the right pistons for this and the comp can end up to high for pump gas so dont use small chamber heads.
This will make it a 406 and a power house with right heads and cam.

[boatermike]

ive actually experienced a 406 and it was good mojo in a 63 chevy truck

[boatermike]

i thought a 406 was a 400 .060 over

[1BadAction]

406 is a 400 .020 over... which is pretty standard overbore.

Maybe I read the post wrong? anyhow, I fixed it. :D

[RLP]

Whats a 400 with 350 (5.7) rod ?
Thats a 3.75 stroke crank,5.7 rod and 400 bore= 406 right ?
Built alot of these engines and the 5.7 rod is the only way to go,but we do get 600 hp out of them.
Some guys use to go cheap and run 350 pistons with the 400 rods and they never lasted.
My tip was use the 5.7 rod its a little longer and will not put as much psi on the side of the cylinder wall and will not chunk the rod
like they are known to do with the short 400 rod.

[1BadAction]

Whats a 400 with 350 (5.7) rod ?
Thats a 3.75 stroke crank,5.7 rod and 400 bore= 406 right ?
Built alot of these engines and the 5.7 rod is the only way to go,but we do get 600 hp out of them.
Some guys use to go cheap and run 350 pistons with the 400 rods and they never lasted.
My tip was use the 5.7 rod its a little longer and will not put as much psi on the side of the cylinder wall and will not chunk the rod
like they are known to do with the short 400 rod.different rod lengths don't change the displacement, never have never will.

The longer rod is the way to go, but the CID is still 400.

[boatermike]

400 with a 350 crank and rods? its all so confusing with one million possible combinations

[1BadAction]

400 with a 350 crank and rods? its all so confusing with one million possible combinations
That's 372 ci, 377 if you go .030 over when you rebuild it.

[Riverman]

To use the longer rod on the 400 a different piston is needed with a higher wrist pin height. These are aftermarket pistons if I remember correctly. The purpose of the longer rod is that it changes the angle that the rod acts against the crank - in other words the rod has a straighter "push" on the crank during the power stroke. This results in greater torque.

The engine on my cruiser is set up this way and it launches the old pig real nice!

[RLP]

different rod lengths don't change the displacement, never have never will.

The longer rod is the way to go, but the CID is still 400.

If ya look he said his block is .030 over 4 bolt block.
Just trying to say best to go with the 5.7 rod they hold up way better than the crapy short 400 rod.

[RLP]

400 with a 350 crank and rods? its all so confusing with one million possible combinations

This combo is what we call a 377,its a good runner also with a little less torque.
I feel like the 383 is a better combo than the 377,it has the 400 crank with smaller piston and to me the 350 block is alot better block
than the 400 block.

[boatermike]

yes the siamese bore 400 is not the greatest for head gaskets and bore stability but isnt it steel crank 4 bolt mains?

[455maveric]

Well i dont think you can go wrong with the 400 but if you are gona go for longer rods go all the way to 6 inch you can get them for $200 new with bushed ends for floating pins not only will the longer rods help it live it will make it preform alot better . I ran a 400 in a race car and used copper head gaskets this seam to take care of the heating problems due to the seamed cylinders I also ran the 377 combo in a daytona 19 jet boat it had a B&M Mega blower on it with 11 pounds of boost the boat ran 85 with out a blueprinted pump