6 good reasons why NOT to supercharge an L27 - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 05-08-2008, 01:21 PM   #11
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Scuffing isn't normal. I'd say that'* another nail in the twisting rods coffin.
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Old 05-08-2008, 04:07 PM   #12
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Rod bearings don't like KR and even if there is no KR present. Running on the leaner side ~12+ will decrease the life of the rod bearings substantially.
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Old 05-08-2008, 05:30 PM   #13
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So does running near 14 psi of boost on an L27 lower end. Very little KR was present...I had up to 3* of it after the PCM conversion, and most of that I think was due to unadjusted parameters. This was one of the reasons why I ran rich on purpose.

Got the entire assembly apart. Guess what? MAIN BEARINGS are toast too. But the cam bearings are fine. So I am uncertain what that knocking sound was, but regardless this engine was well on its way to being trashed.

Crank is turnable, cam can be saved, rods and pistons can be reused, and I can break the glaze on the cylinder walls. Due to some recent changes in budget, I'll rebuild this as an L27 and either shelve it or store it for another time. I think the SSE finally found a new home
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Old 05-08-2008, 09:26 PM   #14
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Looking forward to the piston pics.

The side of the pistons as you describe them would be the normal side for wear (the thrust side of the front bank is the side closest to the intake manifold, exhaust side for the rear bank.) When you say "scuffed"..is it just the original machined marks worn off the skirts? Or vertical lines cut into the pistons?

The rod bearings took a beating.
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Old 05-08-2008, 09:45 PM   #15
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Pics may have to wait for a few....my dog ate the freakin' memory card reader.

Stupid dog.

Curt...yes, there are vertical lines on the skirts that parallel the rods. I noticed that there is lots of side-to-side play with the rods...I am guessing that is supposed to be there and would probably be just fine under NA applications.
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Old 05-08-2008, 10:02 PM   #16
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Quote:
Originally Posted by sandrock
I noticed that there is lots of side-to-side play with the rods...I am guessing that is supposed to be there and would probably be just fine under NA applications.
Not really..the normal spec side clearance on the connecting rods is 0.003" min to 0.015" max..that'* barely "wiggle" room...just enough that you can feel it, but not much at all.

Since all the bearings are wiped out at this point, the rods need extra carefull attention before reusing them. They need to be measured for runout and twist at this point, they probably got pretty hot running with that much clearance.
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Old 05-09-2008, 11:17 AM   #17
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And to show you guys just how much movement there are in these rods...

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