I recall Guido (maybe someone else) saying stock 400 blocks can take up to around 15psi before they crack. Is this correct and/or what is the "general" limit of these? TIA

 

Boost alone is very rarely the cause of a cylinder block failure with the proper preparation, typically head gaskets will fail before anything else. Generally, detonation and/or excessive rpm is more detrimental.

 

use splade caps

 

It is commonly accepted that the 400 block is not as strong as a 350 casting due to thinner cylinder walls. The machine shop I had my Dart block prepped at explained to me that the factory 400 blocks, even with splayed studded mains, can take up to around 650ft/lbs of torque and they start pulling the crank out the bottom.

Tory Hess of this board broke one in his Formula with a big Vortech on it. Split the cylinder wall open.

I didnt want to go through that, so I ditched it and bought a Dart block.

 

That's what i was looking for, thanks guys