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Discussion Starter #1
Hallo everybody,
I've read that the subject has been discussed a few times in the past, but now I'm looking for informations about where I can find a set of main bearings for my 2L, wich had the famous #2 and 4 bearings drlilled for direct oil feed. Main suppliers like IAP seems to have only plain shells.
Can anyone give me a suggestion?

Many thanks in advance

Alberto
 

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I don't think you want grooved bearing for #2 and #4 journals. All you need done is for the upper shells to be drilled so that the hole in them lines up with the hole that the machine shop created in block.

You need to be gentle with the bearing to not bend or crush it. Drill the hole a little larger than the new oil hole in the block. deburr the hole.

The only reason the other bearings are grooved is so that the oil supply to the rod and then the #2 & #4 mains is constant as the crank turns. Your block drilling eliminates the need for that.

Clevites website goes into how grooving bearing lowers the protection at engine bearings.

I have drilled 4 blocks so far and prepped the bearings, so far, so good.

Greg
 

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Discussion Starter #3
Thanks Greg,
your informations are precious for me.
The only residual doubt I have is that the oil film between journal and bearing have low and high pressure points, because of the journal self-positioning not concentrical in the bearing during rotation. The oil feeding hole is supposed to be placed in the low pressure zone: will it be in the right position?

Anyway, your experience seems to show that everything works fine, and that's a really good starting point.

Thanks again

Alberto
 

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I have had the same experience as GregSef. Just drill a hole in the stock bearing shells, and you're done (after drilling the block, of course).

the oil film between journal and bearing have low and high pressure points, because of the journal self-positioning not concentrical in the bearing during rotation. The oil feeding hole is supposed to be placed in the low pressure zone: will it be in the right position?
Keep in mind that the crankshaft will still supply oil to the #2 and 4 mains. Your new passages in the block and #2 and 4 upper shells just a) supply additional oil, and b) provide a back-up in case the crankshaft passages become obstructed.
 

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Discussion Starter #5
Yes, your considerations sound reasonable to me, one of the issues I was considering is that the two bands of the grooved bearing surface will support higher load peaks than a plain one.
Even if the engine will not be raced, it has a prepared 155 head, and over 7000 rpms are expected, so this point could be relevant.

Many thanks everybody, I will post some pictures of the work when it will be done.

Alberto
 

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Read this technical bulletin from Mahle Clevite. Their website has a wealth of technical information.

http://www.mahle-aftermarket.com/C125790900540AC0/vwContentByUNID/856F9F7662D109D8C12579BC005E5D93/$FILE/TB2051.pdf

Greg
 
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