Quote:
Originally posted by psfred
Duke:
The casting was a very poor design, so that piston clearance vanished on slight overheating (I think the problem was mainly no or too small a coolant passage between pairs of cylinders, but no longer remember). Get hot sitting in traffic, loose a bit of coolant, and the cylinder walls got eaten up. Certainly, the first two years or so of production all died by 30,000 miles or so. If you got a good one, they ran fine, but that was a crapshoot.
Rover bought the Buick V8 version and still make it.
Peter
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The problem with the early Vega blocks was the etching process. It was inconsistent. The process was supposed to be etch away about half of thou of aluminum, leaving a pure silicon wear surface, but it was inconsistent - some areas weren't etched and some were over etched. If there was surface aluminum the rings would tear it off and score the cylinders. Overheating exacerbated the problem. On my '72 Vega GT a piston/wall scored and broke a piston skirt on a cross country trip at about 40K miles when it was two years old. I was close enough to have a friend flat tow me home. I bought a new fitted block and rebuilt the engine. Two years later I got my parts expense refunded under GM's "secret warranty" that got them in trouble with the FTC.
The Buick 215 had iron sleeves, so was a totally different design.
Porsche was the first to pick up the GM/Reynolds 390 alloy block for the 928. They improved on the process that GM had mostly perfected, but the bad publicity from the early Vegas caused GM to abandon the technology. Mercedes picked up the technology in the early eithies and BMW followed not long after.
Interestingly, the current Mercedes V6 and V8 engines use cast in ALUMINUM liners in a cast aluminum block. All I can figure is that they decided the block would be better with a different alloy than what is best for the bore wear surface, and I assume it's still Reynolds 390 or something similar.
Duke