Retoactive update.. last month when I got my block back and started plastigauging, everything I checked was within spec. Main bearings were all 0.0025" on the green, so I lubed up the main mearings and installed the crankshaft but noticed binding on cap #3. I followed the GM manual with exception of the outer studs, which I had inserted without nuts at the same time that I inserted the inner 12mm studs with nuts. When the #3 was in place and the 12mm studs torqued to 10 ft-lbs the crank would bind on the front upper / rear lower thrust bearings and I could not fit a 0.004 feeler gauge, even after tamping the crank to align the thrust bearing surfaces. I removed the 10mm studs and reseated the cap, then the crank was no longer binding but the 10mm studs would not thread in.

I pulled the cap and looked closely at the alignment of the new splayed main holes and discovered they were out of alignment, enough that the 10mm studs were pushing the cap alignment out of spec for thrust bearing clearances.

I took an airphoto of the webs, skeched up lines and approximate dimensions in CAD, and sent the above picture to the machinist who originally did the work. They indicated the drilling and tapping was outsourced to a subcontractor who were not engine specialists, and they must not have understood the importance of hole alignment forward/backward on an engine block. They took the block back with the main bearings, caps, and crankshaft, and returned them to me the same day with the issue fixed and the crank re-polished free of charge. They fixed the #3 alignment issue by offset reaming the outer holes on the #3 cap, similarly to the below sketch.

Once I got back home, I installed the crankshaft again and aligned the thrust bearing caps, the upper and lower thrust surfaces aligned perfectly. With the crank forced forward, the 0.004" feeler gauge would fit but the 0.010" would not, on both the upper and lower thrust surfaces. Same withe the rear upper and lower thrust bearing surfaces with the crank forced backward. I removed the caps, cleaned the 10 mm splayed holes with an ARP thread chaser, swabbed with q-tips, and applied Permatex Maximum Temperature Thread Sealant to the M10 studs and bolt holes (since they penetrate into thewater jacket) , then re-seated the caps again.

With the crankshaft caps and studs installed, I torqued the nuts in the following torque sequence for ARP studs on splayed mains:

I re-checked the crank for binding and the thrust clearances, was easily turnable with one hand on the nose.
I then went on to installing the pistons and connecting rods. The new pins and small ends of the rods were measured by the machinist to be within spec, same with the big ends - they measured and told me that my standard size upper and lower bearings would work just fine. I plastigauged the rod bearings and like the main bearings were all close to 0.0025" on the green. Side clearances checked out as well with the feeler gauge.

Piston rings were measured and gapped by a machinst, but I re-checked in the cylinder with a feeler gauge before installing on the pistons. I used mahle bearing guard on the bearings, lithium on the cam, pins, and gears, and 2-stroke oil on the pistons. I ensured the dot stamped on the top ring was facing up and the gapless #2 ring was on the bottom.
![IMG_0004[1].JPG IMG_0004[1].JPG](https://www.thetruckstop.us/forum/data/attachments/54/54113-c52a359a66a57c5b65d00fe103aa2f12.jpg?hash=xSo1mmalfF)
Timing gear installed (lubed with white lithium grease after photo).
![IMG_0048[1].JPG IMG_0048[1].JPG](https://www.thetruckstop.us/forum/data/attachments/54/54114-78e6cf2786f0c1c627b02b25ff84fa2a.jpg?hash=eObPJ4bwwc)
I picked up new old stock 5234530 valve lifters. Submurged in diesel overnight, primed in the morning, submurged in lucas, then installed. I coated the lifter guides and retainers in lithium grease and installed.
![IMG_E0079[1].JPG IMG_E0079[1].JPG](https://www.thetruckstop.us/forum/data/attachments/54/54115-cdb6243b907b7b6bf7abf8714a512909.jpg?hash=zbYkO5B7e2)
I also installed the timing cover, 251603 water pump, and DS4-5288 injection pump, using mahle gaskets and thinly brushed Parmatex Hi-Tack gasket sealant onto all contacting surfaces. Thankfully I marked my old IP and timing cover with a cold chisel prior to teardown, so I just re-aligned the marks. Time shet should go smoothly, but I have OTC-6087 wrenches, J-29872 and an Auto-Enginuity scanner just in case.
Tomorrow if I have time I will clean the mating surfaces and install the heads and studs. I already chased and swabbed the block threads and will use Permatex Maxumim Temperature thread sealant on the coarse stud threads.