Most Power from Stock 400-509 casting?

[GARY C]

FWIW GM decided to save a few bucks and retain the open head bolt holes in the 400 blocks. They also sculpted cylinder wall material at each of those head bolt holes, so the wall thickness in those 5 areas is pretty damn thin, under 1/8”. The Dart block does not suffer from this design flaw.

Design flaw???? Heck if you were to design a 265hp 400 cubic inch engine.. mind you only 265hp and has to be mass produced. would it be beneficial to your company to have .300" cylinder walls, blind bolt holes.. essentially retool everything? No.

The LS engines have some Racing related design problems. But both engines do exactly what they were designed to do.

IM SURE THE OP IS WELL AWARE A DART BLOCK WILL HANDLE MORE POWER. HE ASKED IF 600 HP WILL LAST IN A BRACKET DEAL. THE ANSWER IS YES

Why would they have to "Retool" everything if they if they had just designed the block correctly before tooling?

It really makes one question the level of their design engineers at that time especially considering that they never saw the advantage of the 400 block and it's potential diversity while spending massive amouts of money to cast different blocks for different cubic inch engines that all became useless scrap.

[steve cowan]

FWIW GM decided to save a few bucks and retain the open head bolt holes in the 400 blocks. They also sculpted cylinder wall material at each of those head bolt holes, so the wall thickness in those 5 areas is pretty damn thin, under 1/8”. The Dart block does not suffer from this design flaw.

Design flaw???? Heck if you were to design a 265hp 400 cubic inch engine.. mind you only 265hp and has to be mass produced. would it be beneficial to your company to have .300" cylinder walls, blind bolt holes.. essentially retool everything? No.

The LS engines have some Racing related design problems. But both engines do exactly what they were designed to do.

IM SURE THE OP IS WELL AWARE A DART BLOCK WILL HANDLE MORE POWER. HE ASKED IF 600 HP WILL LAST IN A BRACKET DEAL. THE ANSWER IS YES

Why would they have to "Retool" everything if they if they had just designed the block correctly before tooling?

It really makes one question the level of their design engineers at that time especially considering that they never saw the advantage of the 400 block and it's potential diversity while spending massive amouts of money to cast different blocks for different cubic inch engines that all became useless scrap.

I think you are being a little harsh on GM,
In 1970 I doubt they were even worried about the performance side in mass production of the 400ci block.

[PackardV8]

In 1970 I doubt they were even worried about the performance side in mass production of the 400ci block.

For true. In 1970, if you wanted performance, GM would sell you a big block. The vast majority of the 400" SBCs were two-bolt main, 2-bbl carburetor, single exhaust; just people movers, never planned or sold as a performance engine. That we're having problems when we choose to take it to 2X - 3X the designed power level is all on us.

[rustbucket79]

In 1970 I doubt they were even worried about the performance side in mass production of the 400ci block.

For true. In 1970, if you wanted performance, GM would sell you a big block. The vast majority of the 400" SBCs were two-bolt main, 2-bbl carburetor, single exhaust; just people movers, never planned or sold as a performance engine. That we're having problems when we choose to take it to 2X - 3X the designed power level is all on us.

My point exactly. Wasting time building a performance engine for today’s cost and people insist on messing with 50 year old castings. SMH

[econo racer]

Where I come from we call them good seasoned blocks I have a standard bore 400-509 block. That makes it thicker than most.

[rustbucket79]

Where I come from we call them good seasoned blocks I have a standard bore 400-509 block. That makes it thicker than most.

I wish you luck.

[econo racer]

Rust bucket I know what your saying. A lot of times what breaks a stock 400 block is a bad tune. Been there done that. Was all my fault.