400 Head Steam Hole Questions

[69-er]

I've never messed with 400 SBC's. My question is two part.

Can any SBC head be drilled for 400 block use?

And, can a head that has steam holes be used on a non-siamesed block?

My guess is yes on both.

I just thought of another. What is the max bore that is generally acceptable on a 400? Some say .030", others say .060" if the block is sonic checked. Is that still the norm?

Thanks!

Larry

[dynoman14]

99% of all overheating problems and cracking of 400 blocks and heads come from folks not understanding how much cooling siamesed cylinders need. My 400 SBC copper head gaskets have 16 new water holes in them with another 12 original holes blocked off.

You can drill the heads if you know what to do with different head castings to hit water. You will learn by trial and error on finding the water jackets or have it done by a knowledgeable head machinist.

Sonic testing a block will let you know what you can do, I have gotten some old 2 bolt blocks as much as 4.200" while maintaining about .100 wall thickness. You will need to re-center the bore off of the sonic check and not the center of the original bore if you want to go over .030".

I have used 20-30 stock 400 blocks in ARCA engines up to 750HP in an effort to save weight. With proper preparation of the mains, oiling system and cooling system they will run fine. I am currently converting 10-15 of those engines to Drag applications because of the lighter duty cycling.

The big bore engine really love alky if you clearance the bores for additional air and fuel flow and use small combustion chambers in the head and the right dish piston for the head to make power.

Got some old 18* Cup Heads down about 35 cc's 430" and making 16:1 and loving VP Meth, making an easy 800hp with an 850 carb. They also love a 250shot which we will dyno pretty soon to see what numbers it really makes. Quarter Master results actually come up with more HP than the shot on the big ALKY engine.

[Egoracing]

750hp on a stock block! HA!!!!

[joeltjen]

heres what i run.... 817 block- plug the steam holes -3/4 pipe plugs in the big deck holes and drill to hole size in gasket. splayed caps and strap the back and front caps. world products sportsman II heads, 64cc, and we cant touch 'em. 1004 felpro blue head gasket. j and e high domes resulting in about 15 to 1 comp. gives about 590 horse on alky and 75 shows between rebuilds. .040 is as far as we go, you could go .060 if it was a 9 to 1

[hpontap]

If you are making 800hp with 16:1 comp. and the block is not a Bowtie, I would love to watch it lift the heads when it gets hit with a 250 shot even a progressive.
Too much cylinder pressure for a production block.

[parrot69777]

One of the biggest issues a 400 block has is flex. That is why so many of them never last. Everyone I have ever built...block off the steam holes and install deck plugs. Head/main studs are always used. Depending on the application...billet splayed main caps. Up until this past year....never had a block failure with .030-.040-.060 bores. The one block that failed cracked number 2 and the rear main cap (cast gm caps). Found out the crank had cracked on number 8 rod. Crank was a scat 9000 with 3 season on it in an IMCA stock car. Had we used a forged crank....would still be running fine.