Don Terrill’s Speed-Talk

Hey guys, got a 400 SBC thats a 4 bolt going to the machine shop to be checked out. Anyone think this is a bad idea for street engine? I plan on a 10 to 1 engine with a cam that makes power to 6000 and hoping for 475 to 500 horse. Again, its just a cruiser engine, no track time or anything like that. Car is a chevelle with a 4 speed. Any combos?

sounds good to me

Have them magaflux it to make sure it's not cracked at the steam holes. Very common on those engines. If you're using aftermarket heads, make sure to get a 400 head gasket and mark the heads where the steam hole locations are at and get them drilled. One is at an angle and the other is straight up and down. A 400 sb chevy block WILL overheat and crack if this is not done. Aftermarket blocks don't have that issue, but the production ones do. A regular set of small block head gaskets will not work, they must be specific to the 400.

Don't get overly hung up on compression, be more concerned about cam, heads, and intake as a combo. With today's heads, flat top pistons or slight dish pistons will work fine. Pay careful attention to prep and clearances. For street, carb is simple and proven, but fuel injection has pretty much caught up, and a lot of systems are self learning, taking a lot of the tuning out of the picture. High flow water pump and large radiator as well. Lots of choices for ignitions, but a quality aftermarket HEI setup will work perfectly and provide excellent performance. NOT PRO COMP JUNK........

If you haven't already, there are lots of build combos out there that are similar to what you're wanting to do, so do a little research to see what they used to get there. It's not hard to do these days, and can be done reliably....biggest thing is if a part is cheap, there's usually a reason for it. Quality parts will cost more but save you in the long run.

Cracking down the side of the main webs beside the outer main cap bolt holes is common, too.

The weird 400-only length rods are a pain in the butt to get good piston choices it seems.

i always suggest that 400 buildups start with a .020 overbore if you can instead of the more common .030. Everybody including me seems to have a story of a cracked cylinder wall on a 400. Mine was a 377 that lasted 3 or 4 years of a 19 year old kids torture before it cracked. It was at .030
Brian

prairiehotrodder wrote: ↑Fri Jun 12, 2020 10:50 ami always suggest that 400 buildups start with a .020 overbore if you can instead of the more common .030. Everybody including me seems to have a story of a cracked cylinder wall on a 400. Mine was a 377 that lasted 3 or 4 years of a 19 year old kids torture before it cracked. It was at .030. Brian

X2 - OP didn't mention the current bore diameter, but with a 400", less is more. It's also a must to hone with a torque plate. Order your pistons with thin rings. Don't cheap out with the old standard rings even if the pistons and rings are free.

If 500 hp is your goal with a10-5 comp while also having a street friendly idle from the Cam then your going to need heads that have a Intake cfm flow of 265@ .550" lift with a Intake runner of no more then 210 CCs.

No more then 210 CC means that a set of 195 CC heads may need to get ported!

I think your goal could be achieved pretty easily. Like previously mentioned, keep as much cylinder thickness as possible. The plan to keep things at 6000rpm or less will help keep the block alive longer also. Planning on Hyd flat, solid flat, Hyd roller?

This is all great information.

I just got back from the machine shop and block is already .040 over....so the machinist says its junk.

Back to square one.

Looks like if I want to do this, a 400 SBC build...going to have to get a new aftermarket block.

tcb3274 wrote: ↑Fri Jun 12, 2020 12:36 pmI just got back from the machine shop and block is already .040 over....so the machinist says its junk. Back to square one. Looks like if I want to do this, a 400 SBC build...going to have to get a new aftermarket block.

While rare, there are still a few 400"s on their first go-around. When looking for one, don't get hung up on the 4-bolt thing. For street use at your power level, the 2-bolt will be just fine.

At your intended hp level a 383 with a factory 350 block will get you there. No need to go searching for a 400 block.

DeezNutz wrote: ↑Fri Jun 12, 2020 3:08 pm At your intended hp level a 383 with a factory 350 block will get you there. No need to go searching for a 400 block.

Agree. And a later model block with roller cam provisions even better, cheap hydraulic roller candidate, better quality block, 1 piece rear main, no drips....I think more than makes up for the loss of the 20 cubic inches.

If it’s useful at 4.165” bore I wouldn’t hesitate to use it as a mild street engine like you are planning. But that’s just something i would do…

Are the + .040 bores usable with a rehone?