Just curious Formula31... how did the thrust bearing look? Did you check crank endplay?

BT

I have a set of forged 7/16 rods, out of my mag you can have them for $200. includes shipping. J [email protected]

Detonation maybe???

The stock cast pistons looked just fine. I would think they would show some damage before the rods cracked. Unless, it was leftover damage from a previous blow up that I dont know about. Now, I better have the crank magnafluxed too.

Endplay.
Side clearance.
Size of crank fillet.

Something has been pushing on the rod in a sideways manner - hard.

The rods are junk. BUT check and recheck EVERYTHING before you put it back together.

Will do, the crank is still in place. I only pulled #1 main to check if standard before I ordered bearings. Ill check end play now. Wouldnt the bearings show something? The look perfect. So far. havent check the rear main yet.

F-31, check them with dye penetrant, magnafluxing or Zy-Glo. Don't just assume they're bad, know for sure. I've never seen rods crack here before (doesn't mean they can't just that I've never seen it). Also, if you do replace the rods, you'll want to install ones with the same rod bolt diameter. If you have 3/8th bolts now and you switch to 7/16th bolt-equipped rods you'll need to rebalance the rotating assembly.

OK, crank end play .009 good. all mains looked good. thrust surfaces on #5 barely touched. Crank filets look right.

Dave, I can stick my fingernail in the crack. Since I am boring .030 over and going from cast pistons to forged pistons, dont I need to rebalance anyway??

I'm with Crazyhorse. If those were cracked as bad as they look, one of the four would have failed. Make sure you get to problem definition!

BT

I'm supprised you don"t have one through the side of of the block. Never seen that many cracked in one engine.