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mb911 mb911 is offline
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Join Date: Jan 2003
Location: Burlington, Wisconsin
Posts: 9,289
Originally Posted by patkeefe View Post
Well, I believe this is a stock Mahle forged, as from what I know of them, the cast pistons were with the Alusil cylinders. BTW, I run a Tial wastegate set at 5.8 PSI, and monitor it with a boos gauge, so this engine has never seen excessive boost. The odd asymetrical dome on the CIS piston is note worthy: evidently, it was designed not so much for any swirl effect, but to smush the mixture into the center of the cylinder to optimize the plug firing/burn rate. The evidence of detonation I see in the pistons is on the "short" side of the dome.

GJF, as you suggest, I am guilty of an out-of-the-ordinary event. When I first put the engine together a few years ago, I was carelss on the oil rings. I checked the end gaps on all of the rings, and the side clearances on the compression rings. However, I idiotically never checked the side clearance on the oil rings. I took it to the track after a couple hundred miles on the street, ran it for abot 12 track miles, and it was smoking. I brought it home and disassembled the top end of the engine. Part of the smoking problem was due to the lack of reliable turbo drain. But, I found that I had put in the later SC rings, which are 0.5 mm less thick the old SC's. So, basically, I was a moron and put in the wrong rings, and ran it for 300 total miles. I installed the correct rings, and have lamented this ever since, and can't help but think this had something to do with my current problem.
Pat as a convert myself I can tell you with certaintee that mahles are not forged. the best solution is to send the rods out for offsetting(costs about 180 from supertec) and increase to 23mm then put some stock 930 used p&C's on there for about 400-600 bucks and be done with it. the recurve is not required at all as I ran an sc dizzy with great success for 5,000 miles till I went to twin plug.. My setup has been rock solid since going 8-1 JE's though but I would probably go less CR next time so I can have more boost

Current project 73 914-6 Gt project rusteration 2.4 ,heat exchangers, oil tanks, etc
Old 11-09-2008, 04:08 AM
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