rlm328

I couldn't remember if it was right or left. I stand corrected.

333pg333

Sounds like it's both but with the motor canted over like it is, makes more sense to me that it's LH corners.

V2Rocket

If you have an external (dry sump) pump...I wonder if you could drill into the block and make new oil passages, directly to each main bearing that then feeds its rod bearing. Make a common "manifold" with little oil tubes coming off of it at the pump outlet.

Forget the less than ideal oil gallery geometry, pickup failure, etc. Just run new pipes. Mechanically injected Diesel fuel hard-line should work.

Droops83

I agree. Maybe that is why I don't run the Roval at Auto Club/CA Speedway that much!

Now, I don't wheel-to-wheel race my '86 951, but I have driven LOTS of very hard time trial laps at Big Willow, where the RH Turn 2 is nearly 10 seconds long and at almost 90 MPH.

3-4 years ago, I pulled the original rod bearings with almost 150K total miles, and they looked almost brand new after thousands of track miles. At the time, I had no oil pan or pickup mods whatsoever, I just made sure to keep my oil level at the full mark, and I use quality oil that can withstand high temp racetrack conditions.

My car was meticulously maintained from day one by the original owner, a customer of mine from whom I bought the car almost a decade ago at 88K miles. I think this is a huge factor. I know that the 944/928 crank oiling scheme is not ideal, but the only time I have seen connecting rods coming through oil pans of 944s is at 24 Hours of Lemons, and we all know how well maintained those cars are!

Oh yeah, my engine is also 100% bone stock and I tend to shift at 6000 RPM except on certain straights where it is advantageous to hold the gear for longer to avoid a superfluous upshift then immediate downshift; these are NOT high-RPM engines and never will be!!! The stock 951 engine has good midrange torque, so long sweeping turns can be ran in a gear higher than would be normal with other platforms (I run Turn 2 at Willow in 4th, though I could be at the very top of 3rd).

My car punches well above its weight, but I have run mostly on street tires. I know a lot of you guys have wider, stickier tires and some run decent aero packages. Combine that with higher cylinder pressures and more RPM, and the #2 rod bearing lubrication deficiency probably becomes a lot more apparent . . . .

Just my $0.02 . . . .

Chris

Humboldtgrin

Michal Mounts has done the reserch. He has found a better quality rod bearing but the rods needs to be machined to accept the better quality bearings. I plan on using his service on my next build. And oil quality should be considered. Millers oil is a good quality oil to look into. i like Vans or Voith's (I forgot) idea of drilling a secondary feed to the rod bearings from the other main bearing in previous discussions. Baffles, oil pickup rings, crank scrapers, screens are helpful to lower the aeration affect in the oil. Dry sump would be the best system to keep the aeration to a minimal. The #1 cause of oil break down is aeration of the oil. I think that choosing the right oil is a good start.

Chipster

Mark,

I have been wheel-to-wheel racing my 86 turbo for 12 years with no bearing issues. The motor is stock except for a Lindsey Racing 3X oil cooler. No scraper, baffle or dry sump. I replaced the rod bearings in 2010 while fixing a leaky pan seal and they looked practically new. I run Valvoline 20-50 full synthetic racing oil exclusively and I'm OCD about making sure the oil level is at or slightly above the full mark before I go out on track.

I've raced at 10 different tracks (with both long LH and RH turns) over the years in various conditions and regularly push the tach past 6500 rpm.

Willard Bridgham 3

The most successful mod I have heard from my fellow track-rats is to replace the stock Porsche bearings with racing bearings.

hacker-pschorr

Your engine has more than just a drilled crank, I know you know this and yet you never go into details when starting threads like this.

Mark left out that his engine has:

• Moldex Crank - designed by the engine builder, only two others have been with these specifications and both are in Green Bay waiting to be built.
• Chevy small block rod bearings
• Connecting rod side clearance is larger than stock
• Oil passageways in the block have been modified
• Nikasil coated

It should be noted the person who designed and assembled this shortblock is a very well respected and known local engine builder locally to me. This engine was precisely balanced and care taken to "clean up" any areas he felt necessary to increase the longevity of this engine under racing conditions. Everything was polished, radiused, measured, re-measured and measured again after a full assembly, diassembly and re-check of the hardware.
Todd knew what this motor was going to be used for and built it accordingly.

This engine is the textbook definition of a balanced and blueprinted race engine. Not an off the shelf 928 motor with a drilled crank as Mark often presents it as.

It's about as stock as the "Chevy" engines running in the Corvette's at LeMans.

He's not looking to build anything. The topic of losing 928 engines due to bearing failure has been going on since before the internet.

Mark has the opinion that as long as you use proper oil and proper warm up techniques, a 928 engine can withstand any track with any level of driver behind the wheel. Most in the 928 world simply do not agree with this. Mark uses his success at the track as proof of this theory and threads on the topics get overheated on a regular basis.

In a few of these threads, it was suggested to Mark that he research the 944 world in his quest to find out why people are losing motors. That is where this thread comes in.