Why does the block split at high hp?

GreenMustangGt said:

I was just reading an article in the new MM+ff and they said that the reason the 5.0 blocks have problems holding upped power levels is due to the crank. I guess to balance at 50oz, they must remove material from the front part of the crank, and this actually makes the crank weaker. They went on to say that the new 4.6's and 350 chevys, etc are all zero balanced on the crank, so there isnt much material lost and that is why they can take soo much hp before the block splits, like the 03 cobra for example. which is only a regular 2 bolt main block. is that the reason the blocks split? due to the crank snapping after #1+5 where our's are balanced, and then splitting the block? if so, possibly using a zero balanced assembly could buy some more hp? also is there a way to strengthen up the stock block?

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Modular blocks are 6bolt mains, 4 on top and 2 on the side.

LS1's are 8bolt mains if I am not mistaking(dont quote me, they might be 6 as well though).


ZERO balance and what not have nothing to do with the blocks performance.

The block ITSELF is the weak point regardless of what internals are implanted, as they usually crack from the 2+3 mains and proceed upwards to the most weak point, which is the lifter valley.

OLDER blocks(74's-lower) are myth'd to hold more power... not sure if this is factual information or not, or the person has held their rev limit to a minimum throughout its life.

Anyway I got a Stock Cobra crank in my 98 Cobra, Probe Pistons and H beam rods and am closing in to 700rwhp within the next week or so once I get a new blower in.

If you wanted to get a reliable block for 600-700hp(sometimes this number can exceed depending on prep work to the block), then you should look into a MEXICAN block. This will require the use of a small radius camshaft and some other modifications, such as hydraulic conversion.

Oh yea, a lifter valley girdle will do NOTHING because as I stated the crack begins at the mains and go UPWARD. A girdle cannot stop a hairline crack that has begun... nor can it prevent a crack as there is still a lot of force that can get to the valley because there is STILL AN OPEN SPACE UNDER IT!.