Viking427

I've got a 400 block (circa 1970 me thinks) that has factory 4 bolt mains. I picked this up many years ago when 4-bolts were preferred over 2 bolts regardless of application, and long before knowledge of the main web cracking issue on factory 4 bolt 400's came to light. I'm now considering using the block as foundation for a mild 406 project (350-375 rwhp, alum. heads, street duty) but am unsure if the block is a wise choice. The block was essentially free so I'd like to use it as is if it'll meet my requirements. Should I be considering installing ARP main studs in order to gain the reliability of a 2 bolt (or splayed 4 bolt for that matter) block...or just look for a different block altogether...or am I twisting my panties in a knot over nuttin' :rolleyes:

CFI-EFI

Nothing will make this block as strong as a 2 bolt. The "meat" just isn't there in the main bearing webs (bulkheads of the block), itself. Studs wouldn't hurt, but concidering it is what they screw INTO, I think they would be of minimal benefit (weakest link rule) if not a waste of money. I DO think this would make a reasonable foundation for the mild street application you have in mind. Good luck and...

RACE ON!!!

Monty

:iagree: At that power level, it won't matter any main bolt/stud arrangment would be sufficient. 4-bolt and especially splayed 4 bolt would be way overkill - not that that's a bad thing though ;).

The issue with regards to factory 4-bolt 400 blocks being weak is overmphasized. Most people would never have problem either way.

No Go

By the way, the casting date should be on top of the bellhousing mounting flange-just behind the rear intake manifold mounting surface.

Month Day Year using letters and numbers.

I would use the block in a heartbeat :)

sinistervette

The factory quit making the 400 4 bolt blocks because of the main web crack issue. These were never offered in any form of a performance engine, period. If they were cracking as stock, they wiil crack even quicker with any form of performance mods. It is not a fact of weak bolts, so any bolt or stud you would use would make absolutely no difference, the block is the weak part. I've had 3 4bolt 400's in the past, and they all broke. These were 1 stock unit in a 79 3/4 ton 4X4 used to pull my race car to and from the track, the other 2 were engines in my race car. I had not learned/heared of the mains cracking before this time, and as soon as I started asking around found alot of info about them being weak. Since then I've run numerous 400 blocks in various cubisc inches and applications that were 2 bolts and/or converted to splayed 4bolts. They have all never broken in the main webs. I personally would sell it to someone that thinks they really need or trust the factory 4bolt block and replace it with a 2 bolt one. 2bolt will be far stronger and plenty for what you are looking to build. Good luck. :cheers:

Caboboy

I agree with sinister 100%. The block is probably just fine........ probably. Since you're at the bare block stage and going to invest a few grand, why take any kind of chance at all? It's a no brainer for me........ at this point there's virtually no cost difference whatsoever. Good luck to you no matter what your choice is! :cool:

The Money Pit

For what it's worth I run a 1970 400 4 bolt block pushing about 500hp. Used ARP bolts throughout,and so far so good.

71coupe

I thought they killed that motor because of smog issues. The 400's biggest (or most common) problem was the cyls would not stay round when the engine was up to temp. The "normal" oil consumption for a new 400 was around 800 miles per quart. (compared to a 350 at around 1100-1200 mi per qt)
The oil getting past the rings caused a host of other problems including detonation.
If i had a good 400 block I would go for de-stroking it & putting enough hard blok in it keep the cylinders more stable.

71coupe

I had to double check the info I gave on the last post. According to GM, the oil consumption issue was not related to the simeised bores (which was 700 miles per qt, not 800). The head bolts caused the deformity of the cylinders. They said that when they enlarged the bore the head bolts were very close the the cyl bores. On teardown, they would find shinny areas in the cyl between head bolts where the rings lost contact. They also mentioned something about bulkhead cracking issues.

black bart

People are quick to spend your money. The block will be fine for your stated power. The block don't break at the point where the bolts go in anyway they break up next to the cylinder wall and that will happen with two or four bolt.
If you use studs instead of head bolts and use torque plate to hone it and use studs in the mains and you will not have a problem.

The Money Pit

They killed the 400 smallblock because they already had the 396 and 454 bigblock.Kinda wish they kept it around.