425 Engine Mileage - What is Normal Cylinder /Bearing Wear

[JZRIV]

This is a question to those with experience rebuilding engines.

I am starting a resto on a 66 Riviera GS and there is some uncertainty on the actual mileage. Seller stated and swore 27k but I naturally assumed 127k. Despite the cars neglected condition, I began to identify signs that it could be 27k but none of those signs were necessarily a smoking gun. Since I prefer to rely on facts VS emotion, I felt the real answer would ly in tearing the engine down and documenting wear which should define without any doubt a 100k mile swing in mileage.

What would you expect as far as cylinder wear on a 127k mile Buick 425 nailhead? Also what would you expect the rod bearing wear to be?

Cylinder factory spec is 4.3125. The ridge measures 4.313 so its factory bore. I checked 5 locations in each cylinder and the average is 4.3152 with the highest reading being 4.316 over all cylinders. The rod bearing journals are factory spec so crank has not been cut. Clearances checked in at .002 to .0025. 002 to .0023 is the factory clearance specification.

Thanks in advance for any thoughts on this.

[Guest 40series]

Those measurements are a little too far out for a 27K engine and tight for 127K but still possible. I would palce my bet on 127K. What does the carrier bearing in the driveline look like? Front brake drum dimensions. These are parts that show age and mileage very well.

[Reatta Man]

Several factors to keep in mind:

1. Older oils were light years behind modern oils when it comes to antiwear properties.

2. Some diehard owners believed in using non-detergent straight weight oil back in the old days, which is even worse on an engine.

3. Planned obsolesence was running at full speed back then, which may have translated into LOOOONG oil change intervals; "hey, I'm going to only have it a couple of years, right?"

4. Factory tolerances were much wider so you could easily have 10-15% variance from spec on even a brand new engine back in the 60's.

Based upon all of that, with the numbers you reported, it sounds very possible that you have a 27K engine. If so, you have a REAL treasure on your hands!

Good luck!

Joe

[Dandy Dave]

I agree with Reatta Man. The bearing tolerances are right where they should be. The cylinders are not that far off either. When an engine is run the cylinders will run in and "Glaze" or "Work harden". I would put it back together and run it. Dandy Dave!