[Prowbar]

Spent the last weeks measuring, prepping and getting everything ready for re-assembly.

With the new NOS bearings, rod clearance is .003" and the mains are .003"-.004". Wish they were a little tighter but within spec. Where I got the weird rod bearing clearance readings from I could not tell you.



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Replaced the old cam bearings with the Durabond GM5 cam bearing set. Made my own installer tools on the lathe. All went in smoothly except for the no. 4 bearing. It's too tight, can't get the cam in. Ended up putting the old one in. It was still in good shape. Clearances are looser than spec, around .004" while max spec is .003".



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Ideally the block needs an overbore, it has about .004" taper where the top ring reverses linear motion. Since oversize pistons and rings are nowhere to be found sleeving would be an option but that would set me back financially... machine work is overpriced here unfortunately.

I did manage to score new piston rings! I contacted a company here in the Netherlands (THN) if they could help me out. I gave them the sizes I needed and they had them in stock! Unfortunately they didn't have new oil control rings. My old ones can be re-used I think. I got from them a new chrome top ring, 2 cast iron 2nd and 3rd rings. They are all square rings (no taper or bevels) The manual does call for a ring with a bevel, probably to help oil control. Hoping that these new rings do help with oil control, looking at the carbon buildup on the pistons I think some oil got past the old rings.

We'll see. With these engines your trying to do everything to get them as best as you can with what you have. You can get them perfect but it'll cost ya or will take years to find the right parts...

Spent a lot of time prepping and cleaning the rest of the parts. I bought an genuine GM bypass valve for the oil filter housing. I will run the break in without a bypass valve though. I made a bypass blocker, that should force all the oil through the filter. This will be changed out after break-in is completed.
There are 2 different bypass valve pressures:
11 PSI Bypass Valve: OEM Number, 25013759. This is the standard bypass pressure.
30 PSI Bypass Valve: OEM Number, 25161284. This mean for systems that use an additional oil cooler.
I bought the 11 psi version to use. With the right oil it shouldn't pose a problem. I plan on running either a 10W-30, 10W-40 and SAE 30 with ZDDP.



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I honed the block to prepare for the new rings.



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Block is pretty much ready for re-assembly, now the rest of the parts needed to be cleaned up, inspected and repaired where needed.



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Then onto re-assembly. That should be a lot more fun to do.