Can a stock 400 SBC handle a 4.125" stroke or would I have to use an aftermarket block? c.i. comes out to 447 so I think it would be fun. also anybody know what compression height the pistons would have to be with either 6" or 6.2" rods? or if anyone knows to figure comp height required just post that. thanks in advance for any help.

 

Not easily.

Deck height = ½ the stroke + rod length + compression height + deck clearance

Stock SBC deck height is 9.025". Compression height is measured to the CENTER of the pin. Stock SBC pin dia is .927".

I think you'll find that it'll be REAL HARD to fit a pin bore into a piston with a stock block, 4.125" stroke, and even a 6" rod; let alone a 6.2". Not impossible, but also not a real high-reliability situation.

 

good luck finding a cylinder head that will flow that kinda cubic inch without robbing a bank.

 

most Id go on a STOCK 400 block would be a 4inch stroke and thats pushing it.

 

that is what I was thinking. I figured I would need a tall deck block so I guess 4" will have to work. heads are pretty easy choice. I am probably going to use SB2.2 heads.

 

Just curious here...

Are you using a 2 or a 4 bolt block? The 400 SBC is a cool motor, but they suffer from the siamesed bores, which doens't help cylinder distortion, ring seal, or cooling. Also, if you're going to push this motor hard (I'm thinking over 550hp) you're so much better off with an aftermarket block. The 2 bolt 400 block is probably good to nearly 600hp on its own, but the 4-bolt block may end up failing as it is in fact weaker than the 2 bolt block.

Either run a 2 bolt and put 4-bolt caps on it, or an aftermarket block. Have fun and be careful

Ty

 

There are a lot of misconceptions about the siamesed cylinder walls of the 400 block. It actually helps stabilize the cylinder walls. Think Hard Blok.

Cooling is a matter of controlling steam (hence, the steam holes), and having a cooling support system that's up to the task (pretty simple).

The 2-bolt vs. 4-bolt has to do with the straight-down outer bolt holes in the block web - they reduce the load carrying material in that area. A 2-bolt block with splayed outer bolt caps for the 4-bolt is much stronger, because the outer bolt holes go into more meat rather than reducing it.

As for other issues, I know two local racers that lost engines due to cylinder wall failure. One was stroked to 434 (if memory serves), the other was a 377 (350 crank). Both lost cylinders due to inadequate wall thickness of the stock factory casting. The first guy went with a Motown block, which turned out to only be a 412 because they didn't use the 4.00" stroke like he thought they were going to do - he's faster now than he was with the 434. The 377 wasn't built nearly as radically as the 434, but still busted through a cylinder wall going down the track.

I'd highly recommend going with an aftermarket block. If you go with factory block, have the walls sonic checked for thickness, and do a Hard Blok fill (to some level).

 

Just want to clear a couple things up.

Siamesed bores lead to inconsistent expansion of the cylinders as the block wams as a result of uneven cooling around the cylinder body. Since the siamesed side of the 2 bores sees no direct cooling, they remain hotter and expand more than the remaining arc of the cylinder. This leads to less than idea ring-seal unless the machinist accounts for this by heating the block while honing it or doing something similar. It does not make the block stronger like hard-blok - though the importance IS negated if you're running the motor only 1/4 mile at a time - like those who use hard-blok do.

Still - aftermarket block = way to go.

 

I am just getting rid of it it is an 817 block (I think) two bolt. and just going to a 184 bowtie block instead.

 

The 2 bolt is fine up to ~600hp. I'd feel bad if we scared u away from using what you've already got.

 

no big deal definitely not scared. just changed my mind and decided a I like the sb2.2 heads and they seem to be able to make great torque also and with a short stroke so they will rev way higher. I figured the 406was less than I wanted anyway. would have been kinda neat to do a big cube sb2 motor with it though but then I would need the offset lifters and alot more block work so I figured why not just use a bowtie block with 327 (3.250) stroke and some long rods 6.2 or 6.4. this sound like a good idea to you guys?

 

I had a buddy who built a 350 cid Chevy like this...

400 block
327 Crank
HUGE Rods (something like 6.5 inch...they were modified Ford tractor con. rods...)

Its a neat motor. Spins up fast, makes good torque.

Cool idea man.

Ty

 

hahah, i laffed.