harveyf

I have put up a new post on my website regarding how the 944 oiling system is configured, with some thoughts about #2 bearing failures. Enjoy.

http://newhillgarage.com/2013/06/25/...tem-explained/

car_slave

Thanks, that was cool!

16valver

Nice! Good read!

I too have always wondered about the effectiveness of cross-drilling. The only theory I have come up with, is that maybe with cross drilling you have a chance of letting the air out one of the holes and having oil come out the other hole. I don't know... Its a stretch but you've got to wonder...

Anyway, appreciated the article!

Dutch944

Nice write up, always nice to know more about my engine!

fred27

Very informative, thanks for sharing.

Taymar

Thanks for taking the time to put this together, very informative.

aj986s

xX! Very nice article!!!

SpeedyC2

Great stuff, Harvey - thank you for taking the time to put this together!

You explained this to me when I stopped by a few weeks ago, but since I'm not all that bright this article really helped my understanding!

Van

Great pictures! Good job. I think it's also important to note that the #2 journal, being furthest downstream, also suffers from pressure drop and flow drop as oil squishes out to lubricate other spots.

Also, for the mitigation strategies, racers have had good luck with a few different techniques on the crank. One is "cross-drilling" the journal, so the oil comes out in two places to lubricate the bearing, not just one. Second is "perp-drilling", or drilling a hole perpendicular to the existing oil hole in the rod journal, so it lines up with "thrust location" of the bearing - e.g. the part of the bearing that transmits the maximum load to the crankshaft on the power stroke of the piston. Third, another oil-feed passage can be drilled (then capped) diagonally through the crank so another main journal is also feeding the oil supply to the rod journals.

John_AZ

Thanks for the information.
The photos really helped understand the oil flow.

J_AZ

harveyf

Thanks for all the kind replies.

Van, you've probably forgotten more than I than I'll ever know but I just can't get behind the downstream theory. If that were the case, it looks like #3 and #4 are the most downstream. I will say that the large oil gallery or "header" probably maintains a constant pressure and flow capability all the way to its end, so I think each branch to the various crank and rod bearings (except #1) probably gets the same set of initial conditions. So I am really only left with the theory that #2 "selects" the highest percent of air entrainment and that is the root of the problem. We'll probably never know for sure.

BTW, my current N/A track engine has 90 hours of hard use. No cross drilled or perp drilled crank. Valvoline 20W-50 Racing Full Synthetic with Mann filters. Oil changed every other track weekend. S2 oil pan with OEM crank scrapers. Lindsey baffle installed in the sump. Rod bearings changed out last winter at around 70 hours. Knock on wood, rub the rabbit's foot, I probably just jinxed myself for the Chin event at Road Atlanta next weekend that I just signed up for

HICKS

Cool, thanks Harvey!

F40LM

Great write up. Only had time to breeze over it. Look forward to sitting down with it and my spare block and follow along.

9turbo51

Harveyf, thanks for the post, great info.
It seems that the 3.0 blocks (and maybe the 2.7) have at least reduced the #2 rod bearing problems.
I have seen this comparing the rod bearings in my 951 (track car) and my wife's S2 (track car).
We are both instructors and riding with her; she is not "taking it easy".

Tell Mark and Maria, Karl and Renee said Hi, and have fun at RA!

harveyf

Yes, I have first hand evidence that Porsche incorporated a crank scraper in the later oil pans (the one I purchased on Ebay and put on my car). I have heard, although I didn't make any measurements (I should have) that the later oil pans may be slightly deeper such that the oil is a little farther from the eggbeater, I mean crankshaft! We also know from the Lindseys (and others) that there are some minor differences in the later blocks at the base of the cylinder bores to improve the windage between the bores, which might also reduce foaming/air entrapment. But yes, agree the later cars seem to have done something good to help out the rod bearings.

I always get to say hi to Mark and Maria when I sign up. I'll have to figure out who Karl and Renee are and say hi to them too.

I'm thinking about getting one of those orange triangles like they put on the back of tractors for my car to alert all the GT3's as they blow by me on that long back straight