martin D

The delivery point of the oil at the journal is important, see 3rd pic in link
https://rennlist.com/forums/showpost...5&postcount=15

Abby Normal

Thank you for the awesome pictures!

martin D

Marton you old cynic you !

Yes monkey see monkey do can be a waste of time , but if you copy the important parts ( you have to why & what the important parts are) it can be worth while

JEC_31

It is a pretty one.

martin D

This crank looks like it has the EXACT same oil ways as a Chevy.

Brendan
Can you photograph your crank to give the same pic. (with drill bits in oil ways)

martin D

I'm glad they have been of use

atb

I must be missing something.

Don't Martin's pics show the stock oiling pathways. Basically, a cross drilled number 1 main feeding a cross drilled 1/5 rod? If the drill bit entering the rod journal from the left is in a passageway that has been drilled all the way through to number 2 main, then THAT would be new. But the passageways indicated in red are basically the stock oil pathways are they not. If they aren't, how is stock different?

I don't see any pics showing the "drilled like a chevy at 60 degrees" like Martin refers to in his blue line diagram in the link.

marton

Martin posted
Yes, somehow I find it hard to believe that the Porsche engineers who have built successful race engines for generations actually drilled the crank wrong- AND - never changed it.

Marton
p.s. hope the new job is going well?

Mike Simard

Erkka's Moldex is probably the only one you're going to see until someone finds a shop that will do a bunch of plugging.

atb

The purple line is what I'm talking about. Is this what Taylor Machine is basically doing, just connecting each rod journal to the second bordering main journal that it doesn't come connected to from the factory?

123quattro

I can believe it. 924s, 944s, and 928s all exhibit this failure. I've seen the bearing carnage first hand.

marton

I believe the failure; I have seen it too.

I simply have my doubts about the (various) solutions.

Marton
Drilling like a Chevy just sounds like a too simple solution for me

Marton

123quattro

My personal theory is aeration of the oil. Complete speculation on my part. That, and a lot of these engines are now 20+ years old. Anything run hard with that kind of age if not properly maintained will fail eventually.

Vilhuer

Connecting all mains will help even out oil pressure. Question is will it deliver more pressurised oil to 2/6 rods or less to six other rods?

Drilled like Chevy is how many other manufacturers have done to solve similar problems. As this is only one of many oil related problems in 928 engines it can't be complete solution to all problems.

Drilled like Chevy with cross drilled mains takes care of from main to rod drilling without use of grooved lower main bearing half. If escaping from lower half is one more problem in this style crank it will not help much.

I think grooved lower mains are more cost effective solution than crank drilling. That is if they work equally well or better. So far no one who we have spoken about this hasn't said why it would make situation any worse than it already is. Some have said it would not make any difference though.

Mike Simard

IMO the cross drilling of the main, that hole going straight through with the passage to the rod intersecting at the center, is the big problem with a 928 crank. Even a bigger problem than the 2-6 rod journal issue.
Actually I should delete the IMO and put stuff in bold. I've heard enough stories of failures under certain conditions and have done the math of the centrifical force of the oil in that passage and it's potential to overcome the supply pressure at high rpms. The cross drilling IS A PROBLEM.

Here's something that mentions the subject: http://www.rehermorrison.com/techTalk/51.htm