Filled block (torque capacity)

[myclone]

the 4 bolt main is your weak point. The 4 bolt removes too much material from the block and you will eventually drop the crank out the bottom. a 2 bolt main is a much better choice. I have some pics of a 4 bolt that a buddy built. the whole main came out like a slice of pizza!!! the good news is that the crank was not hurt!!

I agree with the above for factory non splayed type four bolt blocks but with a splayed four bolt coversion the meaty part of the main web isnt weakened nearly as much. The outter bolts on a splayed set up end up being mostly out next to the oil pan rail.


toddshotrods,

Just keep in mind that "safe to 1k ft/lbs" is a pretty broad statement and requires EVERYTHING to be top notch from the machine work to assembly to having the block sonic checked to make sure there is enough meat in the casting to withstand some abuse.

Also, be aware that there is no guarentee that a production block wont scatter all over the dyno room at even 700ft/lbs. For piece of mind that the block will hold togeather you need a bowtie block or any number of aftermarket blocks that have beefier castings that the production piece. My point is that there are ppl out there making well in excess of 1kft/lbs with production blocks but they are well aware that at any minute the crank can fall out of the bottom but they are willing to take the risk either for bragging rights or to save a few $$$ (saving a few bucks on a block only for it to go off like a bomb ruining all those high dollar internals still puzzles me but whadda I know ).

Lastly, if we can get a production thin walled 4.3 V6 block with program engineering splayed mains to hold togeather at the 1200+ft/lb level for multiple dyno flogs then a SBC should approach the 1k ft/lb level with less stress.



My .02 FWIW.