Now we lay the crank in position with used bearings for a rotation check. Look carefully at all crankshaft areas for interference. We weren't able to rotate our Eagle 3.750 throw crankshaft a full revolution in the new four-bolt main GM Block (PN 10105123). Out comes the crank and the grinding begins.
This is one area of clearance concern: the block has some relief in this area already but not enough for the long rods and crank throw. We use our high-speed grinder, carefully removing just enough material in this area to allow 0.050 clearance between any rotating pieces as a rule of thumb.
Once everything rotates, we can check the deck clearance. Our block had 0.031 piston-to-deck clearance on the odd bank and 0.029 on the even bank. We need to measure at the front and back of the block, then average the results to achieve 0.001-0.003 piston-to-deck clearance. Some blocks are quite different front to back, so it depends on how the crankshaft is lying in the main bearing saddles. (the piston shown is not a Wiseco piston.)
Now that the crank rotates, and we know piston-to-deck clearance, another trip to the machine shop to drop off the block is necessary. Joe at Gerald and Charlie's operates the surface grinder, and he's setting up the block for surfacing. The engine block is set in place, then it's checked for level on the machine. We found that one side of our new block was not flat and the surfacing was a good thing even if we weren't concerned with the zero deck clearance.
During each pass, Joe feels the block for any strange vibrations. Vibration means chattering, and the block surface can be in bad shape if the cutters started dancing around. Joe explained that he removed 0.004 of material each pass to prevent the chattering and leave a finely finished surface. Decking the block will ensure even compression between the cylinders banks.
While at the machine shop, the engine block was chemically washed to remove minute particles from the decking process. The blue shop towel has brake cleaner on it, and one wipe shows just how dirty the cylinders are even though the block was cleaned. Shame on you if the engine fails from metallic particles and debris; don't expect any machine shop to supply a ready-to-assemble engine block.