Fixed my boost issue.....but spun a bearing this morning

[Checkered vr4]

Is that not caused from an oil hemorrhaging issue? Stock motors hemorrhage oil under 3000rpms at the mains and the oil films are uneven journal to journal. We clearance and balance tighter with aftermarket rotating assembly components to compensate for that very issue. If cut, bob weighted, clearanced, balanced, and assembled correctly I'm of the opinion you don't "pound the bearings out" because they to an extent "float" and remain protected by a uniform film. When bearings deform like that it's because there's a hot spot on the bearing from non uniform oil film thickness. Race engines shouldn't do that. Stock engines, I can see that happening because they hemorrhage oil at low rpms because their clearances can be a little loose and the galleys have casting imperfections.

Are you serious? Race engines shouldn't do that? I had a bearing squeeze so much out it looked like one from an engine that has the thrust and main bearing in one piece. And it didn't spin either. The bearing material smeared on the crank polished off and a new stock size bearing gave me .002" oil clearance and I finnished out the season racing in the low 11's. by the way, factory forged crank, Pauter rods, and Clevite bearings.

[J. Fast]

Are you serious? Race engines shouldn't do that? I had a bearing squeeze so much out it looked like one from an engine that has the thrust and main bearing in one piece. And it didn't spin either. The bearing material smeared on the crank polished off and a new stock size bearing gave me .002" oil clearance and I finnished out the season racing in the low 11's. by the way, factory forged crank, Pauter rods, and Clevite bearings.

and

Yeah, I'm serious. That's a bob weight and oil hemorraging condition. Jack Merkel did a huge performance engine assembly spread on V6 turbocharged builds and illustrated numerous failure conditions related to lack of lubrication He provided illustrations and descriptions on prevention. He modifys the oil passages and clearances at the mains to get more oil to the rod ends and thw bearings dont deform because they stay properly lubricated. When the stay lubed they dont get hot and deform. There's like 8 GM racing tech articles on his findings and modifications about it.

[J. Fast]

It's in one if these series right here with pictures and captions. Not sure which series though.

Buick Turbo V6 Engine Build -- GM High-Tech Performance Magazine

[Chris@Rvengeperformance]

Detonation can destroy any bearing, no matter how well setup your engine tolerances are. The crank flexes. Engine failure 101


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[Chris@Rvengeperformance]

Oh and detonation is an oversimplification. It can be any time you exceed mtbt


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[donniekak]

You can do all you want with a v6. In the end it only has 4 main bearings to support the crankshaft. In a 6g72 they are narrow, and the crank flexes. This wipes the center 2 mains. The center 2 mains are already overtaxed in an oiling system designed for a low rpm, sohc engine putting out around 150hp. Mains 1, and 4 only have to feed one rod, and a squirter that doesn't work(they bleed pressure at idle). Mains 2 and 3 have to feed 2 rods, 2 squirters, and a localized low pressure from the oil galley where it feeds the head. Mitsu tried to fix this with restrictors with really small passages to the heads.

The type of bearing also makes a huge difference in a performance engine. Using regular bearings in an engine making over 125hp per cylinder I've had pieces of the bearing face separate from the backing from overloading. Race bearings solved this issue.
http://www.studebaker-info.org/tech/...CL77-3-402.pdf


I've also read all about the issues overcome with the gm v6 turbo engines. For one thing their oiling system isn't overtaxed from the factory like the 6g72tt. Running the mains tighter on a high torque v6 is not a new secret. The money it takes to do all of the needed maching to do this is usually passed on by most in this community.

[J. Fast]

... The center 2 mains are already overtaxed in an oiling system designed for a low rpm, sohc engine putting out around 150hp. Mains 1, and 2 only have to feed one rod, and a squirter that doesn't work(they bleed pressure at idle). Mains 2 and 3 have to feed 2 rods, 2 squirters, and a localized low pressure from the oil galley where it feeds the head. Mitsu tried to fix this with restrictors with really small passages to the heads.

That is precisely where the 6g72 hemorrages oil off the mains and rods. Theres a couple variations of crankshaft crossdrills and I always wondered if that was another way mitsu intended to redirect oil pressure.

I've never seen a racing bearing elongate in person like the one depicted. I've never had one of my engines show that much localized heat and thrust.

[donniekak]

That is precisely where the 6g72 hemorrages oil off the mains and rods. Theres a couple variations of crankshaft crossdrills and I always wondered if that was another way mitsu intended to redirect oil pressure.

I've never seen a racing bearing elongate in person like the one depicted. I've never had one of my engines show that much localized heat and thrust.

There is also a 3rd revision of the crankshaft. The forged cranks made after 2000 are different. They are balanced better. By better I don't mean tighter tolerances, I mean the counterweight strategy is changed. I always use these new cranks in my builds now.
The revised version is on the right.

[TurboSinceBirth]

That's interesting.

[bboyalan]

Damn, that sucks Mike. Best of luck in diagnosing and deciding on what to do next.