Ok, people! I came to this site by referal of a friend of mine, he said this place is pretty knowlegable, and friendly!
Im a SBC beginner, So im wanting some tried and true combinations. I have two good motors, the first is a 4 bolt 350, the second is a non-siamese 4 bolt 400.
What im wanting is a short stroke long rod motor to turn a lot of RPM. Im not talking 10,000, but short runs to 7000 of 8000 might be common.

Im not afraid to throw some money at this motor, but im not wanting to spend 10,000 on it!

Im going with aftermarket aluminum heads,
Megasquirt EFI,
and a large single turbo.
This motor dyno'ed 750 hp on a 383 with a holley carb and 8lbs boost in a Chevette. The motor wouldnt die, and the car crumbled around it. The guy sold the 383 separate of the turbo kit, and now sold me the two motors, a TH400, and all the turbo 'stuff' So......
I want a quality bottom end that will take high cylinder pressures, and alot of rpm.
Thanks in advance!
SEAN!

 

Well, there are some mistaken assumptions in your post. First is the part about a non-siamese 400 - to the best of my knowledge, that isn't possible. Certainly the factory never made one.

Factory 4-bolts have an inherent weakness in the main bearing web because of the outer bolts reducing the load carrying material. A better bet is a 2-bolt main block that has splayed main caps installed.

Better yet is an aftermarket block like the Motown. You want the engine to live? Start with a superior block. There are too many potential problems with factory 400 blocks to even consider them for high horsepower applications.

Next misassumption is that short stroke = high RPMs. The primary RPM limiting factor is the valvetrain. Parts are available to make 4" stroke SBC's live at 8000 RPMs, so limiting yourself to short stroke based on that assumption is the wrong move.

What do you plan on doing with a 750 turbo'd monster? That is the most important question, the rest is details.

Finally, although this is a good Board for good tech information, this isn't an engine swap question. So, let's move it to Tech/General Engine.

 

The "non-siamese 4 bolt 400" has me wondering also. Unless it's an aftermarket block, there is no such thing. The 2 bolt 400 blocks are better to use. The web around the mains is small and weak. Having a 4 bolt means there's even less metal in the web. A 2 bolt 400 block with main studs is stronger than the 4 bolt block.

As for a short stroke, high reving engine, the most popular is a 377. That's a 400 block with a 350 crank in it. The block will need bearing spacers which will allow the smaller journal 350 crank to fit into the large journal 400 block.

Why do you need a short stroke high reving engine? I buzz my 540 BBC with a 4-1/2" stroke to 7500 with no problems. Of course my entire engine has no factory components.

For what you want to do, I'd also suggest buying an aftermarket block.

 

My friend that sold me the motor said that there were very few of the non-siamese 400's built. 2 bolt of 4 bolt, im not sure. I got to meet this guys ol man. they live just east of Ft. Collins and owned the Case dealership for many many years. Their shop is a full cement floor insulated heat/ac 150x180 shop, and the walls are lined with complete motors. All SBC. There are literally hundreds of motors.... He laughed and said when they (chevy) talked they were changing away from the 350, he bought every thing around that had a SBC in it. I mean their junk yard has hundreds and hundreds and hundreds of chevy pickups out there minus the engine/tranny and all of the driveline. His fleet of service pickups was about 20 or 30 trucks, and he had too much invested in them to just switch over to new trucks.

So we walked along the walls and read tags on the motors till he found one that was ''the good 400'' and then we found a 4 bolt 350 and loaded then with the forklift.

Maybe the 'good 400' isnt a 4 bolt, just not a siamese cylinder? Shoot, im going to have to go over to his place and talk to him about it now....




I want to get the piston speed down, short'er' stroke and a long rod. Ill get custom pistons, because i want to be able to get a lot of cylinder pressure in there without blowing something out. with a cooper head gasket, and the 72cc heads, i should be able to get a long rod 377 with 8.5ish compression, and a good quench/piston shape.
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oh, thanks for moving it, i didnt see this subforum

 

The only "good 400" block I can think of that's not a siamesed cylinder wall would be a BBC 402 engine. It was a factory 396 bored out .030". It was commonly badged as a 400 but caused a lot of confusion so it was rebadged as a 402 which was what it really was. All SBC 400 blocks, and there's only 2 castings, 817 and 509, have siamesed cylinders because the bore spacing is so close that the larger bore could only be obtained if adjacent cylinder walls shared the same piece of metal. The 509 casting can be 2 or 4 bolt.

People get too hung up on long/short rod and piston speed. Unless you're building an all out race car, you won't notice any difference. Every combination works equally well. Trying to do something exotic usually costs more.

My old 383 stroker was an old school stroker. 350 block bored out .030, cast 400 crank, cast 350 pistons, short 5.56" factory 400 rods and rod bolts. I spun the engine to 7000 rpm and ran mid to high 11's with it. It was a well used engine when I got it and I raced it for 2 years before finally throwing a rod.

To use a copper head gasket, you need to get the block and heads cut for o-rings. A receiver groove is cut around the cylinder for a metal wire to be inserted. It's easier and better to use a MLS head gasket. Either the Felpro MLS or the Cometic head gasket. Unless you damage it, it will be the last head gasket you buy because it's reusable.

 

SweeT! I didnt know that about the head gaskets!
you know, i dont know why i am getting hung up on the 400 stuff.... I guess with the smaller bore of the 350, the piston is smaller and lighter. Ill just build the 350 to take the turbo. Cheaper, and less confusing!