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Old 05-26-2004, 06:15 AM
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Tearing down a 74 L82

I tore down an L82 last nite to freshen up for my vette. It appears to have never been apart. I bought it 5 years ago from a guy that had it sitting for 5 previous years(in a garage). The interior looked extremely clean for a 30 yr old engine, no sludge etc. Cylinders appear to have slight crosshatch visible, no ridge. Timing chain loose. While the head gaskets appear to be factory(beaded steel) the pistons look different. They are flattop with a single long valve relief, marked trw(I know TRW supplied forged pistons to GM) but the odd thing is that while they are press fit, they also have groves for spirolocks!
I've never come across this and was wondering if these could be original? The L82 boasted a 9:1 cr ,would flattops(with valve reliefs) put it at that? The heads are 882's (202's).
Any info would be appreciated as I would like to keep the engine as original as possible.

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Old 05-26-2004, 06:53 AM
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According to the info I have it came with these original, but I could be wrong.
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Old 05-26-2004, 09:23 AM
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thats what was in my 77 L-82
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Old 05-26-2004, 12:17 PM
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thanks for the responses guys. One other questionable thing I found: The rod bearings that were in it are stamped with following:
A(in a circle) GM
A 200
.0005 O.S.
3 74

The mains:
1 74-
.0006 U.S
A(in a circle) GM-
Clevite 77

Anyone in the automotive machining business come across this before? I know oversize bearings for a ground crank would have a .010 or whatever the undersize is, but these #'s seem odd. I assume the 3 74 is a date, as the block was cast in 5/74. As I mentioned before, the engine did not look to have ever been apart, even the waterpump was dated correctly.
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Old 05-26-2004, 01:31 PM
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those are common sizes for GM factory bearings as you have, the .0005 is half of .001, example would be if the crank is turned .014, you would need bearings about .011 or .012 thicker than standard bearings, as anything under .001 is not enough, and anything over .003 is too much.
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