Pauerman

I did a main journal flow test with my garden hose and a bare block. I installed the bearing halves and plugged all associated oil passages to get an idea and look at the flow differences once I applied water pressure.

For my tests, I put a restrictor in the forward most main bearing passage and applied water pressure. I didn't notice much difference in flow in all of the main bearing passages. I did the same test without the restrictor and the water flow appeared relatively even all along the block. Given that the oil galley runs the length of the block and it's a straight oil passage, I figured that if there was to be a shortage of flow it would occur at the rear of the block. Visually, the #2 and #3 bearing passages flowed slightly more than the #4, but not my much. For me, this test confirmed that water flow is pretty even at all main bearing passages. The straight, unobstructed oil galley that runs the length of the block has 5 equally length passages that tee off the main galley. It doesn't make much sence as to why the #2 or #3 rod bearing is any more susceptible to failure than the #4.

I've got short videos of these tests, but don't know how to upload them.

StoogeMoe

Pauerman, you're on the right path, but not quite. The problem isn't a static flow problem. The theory is it is a dynamic one. The problem is when the crank is spinning above 6k rpm. The rod journals do not spin on the same center line as the crank journals. Therefore the oiling holes are subject to centrifugal forces that prevent the oil from leaving the holes at high rpms. This is why some believe that cross drilling alleviates the problem. If the oil is prevented from coming out the original hole, then it will be forced out the cross drilled hole. The perp drilling attempts to solve the same problem but also provide oil on the thrust face of the rod bearing where it is needed most.

The other theories are that the oiling problems are pickup related.

Let the controversy continue.

Mongo

I cross-drilled the entire crank. You might as well do 1-4. It's great insurance!

M758

Again,
The reson you drill just #2 and#3 is to balance the flow. It is not to save money. Greg Forhdal did some flow testing on cranks and saw weak flow in #2 & #3 rods in a stock configuration. He then flow tested again with all 4 drilled. Result was more flow in all 4 rods, but #2 & #3 were still less than the others. When he drilled JUST #2 & #3 het got the best flow from #2 & #3 rods and a balanced flow.

If you don't know who greg is here is something posted on our 944 spec forums.

hacker-pschorr

Are there any recommended vendors for crank drilling? My 944S is finally going back together, this is on my to-do list.

For the 928 we have some nifty diagrams like these:
https://rennlist.com/forums/928-foru...ike-chevy.html

Has anyone done something similar with the 944 crank?

joonas

I went with perp drilling #2 and #3 (944S). Still have not got to track though.
I did not build the engine myself so I am getting paranoid about everything (it is my second rebuild in short time).

I installed crank scraper/windage tray and want to add external oil cooler and accusump.
Oversize bearings cost alot so engine rebuild seems pointless if spin few rod bearingas in the year.

This link has some information that I have gathered. Skip the things in estonian language.
http://www.porsche-foorum.ee/viewtop...st=0&sk=t&sd=a

RolexNJ

The only company I have dealt with is Lindsey Racing. They did a great job with the crank in my old 3.0L 8V turbo. As I recall, they outsource it but to a very reputable-local guy. I was very pleased with it too. You may want to reach out to them, they are a Rennlist sponsor too, and ask for Mike.



http://www.lindseyracing.com/LR/Parts/944MACHINE.html

hacker-pschorr

I read a lot around here that if your 944 is not a "hard core" track car, stock is just fine. I autocrossed my 944S twice and it threw a rod bearing....

This rebuild I'm going with an accusump, external Motul oil cooler and probably a drilled crank. I'm not 100% sold on the crank scraper for reasons not worth going into here.
I'm also going to talk to my engine builder about opening up the side clearance on the connecting rods. I'm not sure what the clearance is on the 944, need to find out that info.

I also need to look into that little oil flap in the oil pan. I remember when a friend of mine added that to his race car.

Cool - thanks Rolex

My engine builder has a jig setup for drilling the 928 crank. I have to weigh the difference between having him tool up for mine, or simply out source it.

I'll drop Lindsey an e-mail.