Block girdles, yay or nay

gzig5 said

Hughes sells parts and machining services. Not surprising that they recommend them. I believe that the SBM uses 1/2" mains bolts and the competition are smaller? So maybe not as significant a need for reinforcement? I can see the potential for added stability but I have no idea at what HP level it would become needed. Is a 1/4" thick plate really strong enough? I bet you would be surprised how much deflection can be induced, even into the flat plane. I think if I went to the trouble, I'd be using thicker plate or something that had ribs for additional beam strength.

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Exactly. Look how thick the block and main webs are. 1/4" plate is about like reinforcing a Kevlar vest with a silk cover. Ain't gonna do a thing. At worst it's going to make things worse by interfering with the main bolts mating, and any load it tries to absorb will just be twisting on other caps, not the block.

Now, replace the main caps with one huge cast structure and it might do something. But it would also need a couple dozen fasteners to truly take up any load. I'd add dowel pins between every oil pan bolt and effectively make a "split block" with a 125lbs structural oil pan if I was trying to reduce flex. But then the oil pan bolts are pretty shallow, and not a lot of other places thick enough to take more bolts.

Plus, at that point, might as well fix the oil feed to the crank and rods too by feeding mains oil through that bottom structure.

Seems cheaper to just go with a big block swap, or an aftermarket block at that point though. The deep skirt on a BB does the same thing, even if it kills a bit of power due to oil control.