blown 87

How about the block repair kit that Greg and Steve made?
It damn sure saved my motor.

While I am sure that Greg will never get a lifetime membership, he is deserving of one as much or more than many that have gotten the award.

BC

Joe - thats exactly my thought. We are a community here - with all the normal sorts that come with a brick and mortar community. Some funny guys, some party people, some loaners and lurkers, and some sellers and some takers. We also have some very solid community contributors - people that work hard for the mere sake of working HARD and producing something for this little society.

Greg is one. Louie, Z, Simard, etc are others. If someone wants to be on this list, then contribute what you can. BE part of the community in a productive manner. But never think so much of yourself so as to misunderstand what we are here for.

rbrtmchl

To expand on 90 S-4's post (and if this has already been covered in this great thread I apologize in advance), do other engines suffer from this oil-buildup-in-the-heads problem? It's hard for me to believe that only the 928 engine has this problem. Greg, will you be patenting your solution? I highly recommend it.

atb

So Greg, is this most recent fix another arrow in the quiver along with chevy-drilled cranks and accusumps, or is it a one shot cure all for the oiling issue?

GregBBRD

Adam:

Another great question!

I've always maintained that the 928 design had several issues that caused the bearings to fail. I still think this is the case.

You've got to keep in mind, that every with dry sumped engines that never ran low on oil, we still had to change the Porsche rod bearings frequently (about once a year, in Anderson's race car, when it had Porsche rod bearings.) The 928 factory rod bearings are very, very soft and tend to loose their "crush" in the rods fairly easily. Once they loose their crush, they spin in the rod and things go downhill very rapidly. I've had the opportunity to be very involved (in the past) with 911 race cars and they had the same problems. I believe that this pounding of the rod bearings was caused by very mild detonation...not enough to completely ruin the pistons, but enough to pound the "soft" bearings. Once Porsche provided us with the ability to record "knocks", the problem became pretty obvious, very quickly. A 911 race engine that recorded over 75 knocks in the 10,000 knock count would invariably loose the rod bearings somewhere between 6-8 hours of running. Keep the knocks under 75 and the bearings would last virtually forever.

There were also very subtle clues of mild detonation, in these engines. The piston pins, on these engines, would "batter" on the circlips and raise a significant "edge" inside the pistons. This made pin removal difficult...as the pin would need to be pounded out over this pounded ridge.

The 928 engines suffer the exact same problems. Pounded bearings will always also have piston pins that won't slide out of the pistons, but will need to be pounded on to remove.

For the Porsche Cup Cars, Porsche started out with the stock, soft rod bearings and had the same issues, as the power output went up. They quickly changed to a much harder rod bearing and virtually cured the problem.

In the engines where we use cranks that have Chevy rod bearings, we can also use a much harder rod bearing, and virtually eliminate the pounding problem. Stock 928 cranks with stock rods and bearings are not so lucky. I try and keep the timing very mild and always make sure that the engine has plenty of "octane". I also monitor the metal in the oil filter and change the rod bearings the instant I see signs of increased bearing material in the oil filter.

I've also found that the 928 engine seems to like rod bearing clearances on the slightly "higher" side. Porsche has the bearing maker measure the bearings very carefully and they then "subdivide" the bearings into three different sizes. These are marked with blue, yellow, and red paint markings, blue being the "tightest" and red having the most clearance. At one point in time, it was possible to order the bearings in these specific "subdivisions", but this is long gone. There was an "001, an 002, or an 003" following the main part number. Now the bearings are sold under the same part number and getting a proper size is somewhat random...although they will always mix a "red" bearing with a "blue" bearing, in the same package. Interestingly enough, depending on where they are "on the shelf" of bearings, sometimes you will get yellow bearings. Yellow bearings always come as a pair...never mixed with a red or a blue. I guess they think that the "yellow" clearance will be proper for most engines. They apparently logic that one red bearing with one blue bearing averages out to two yellows...

When I'm building a high output 928 engine with stock rod bearings, I will always "sift" through many boxes of bearings to get the sizes I want. It's a pain in the butt and very expensive to buy multiples of bearings to get the ones you want, but a rod thrown through the side of the block is even more expensive.

This brings us to the "aftermarket" Glyco rod bearings. I used to think that these bearings were different that the Porsche bearings....and I'm still not absolutely sure they are the exact same bearing. The main problem has been that these bearings seem to always be very "tight" and provide minimal bearing clearance. I believe that Glyco makes the assumption that "used" engines will always have some wear on the crankshaft and they furnish "tight" bearings to "counter" the crank wear. The bitch of the thing is that the 928 cranks are very high quality metal and they don't ever seem to wear (unless they fail.) There have been many engines that fail immediately after a "rebuild" when using these "tighter" bearings.

I tend to run #2 and #6 rods slightly "looser" than the other rods, when I build an engine. There are multiple issues with these two cylinders...they are the last to get oil and the first to loose oil, if the pick-up sucks air. They seem to run the cylinders that run the hottest and they are therefore prone to having more "knocks" (as discussed above.) Increased rod bearing clearance seems to help this issue.

There is no doubt that oils which "foam" less and flow well at higher temperatures, while still maintaining relatively high thickness seem to help with the bearing issue. There are several brands of oils that meet these criteria...this has been discussed at nauseating length, in this Forum. I'm going to completely avoid starting another discussion about oils...I'm not sure I can take it again.

Oil temperature is a huge issue. The cars that have the oil cooler removed from the radiator and placed under the radiator will have very high oil temperatures when operated in high heat or in traffic. These cars need high ariflow over the cooler to keep the oil temperatures down. These same cars also will manifest increased camshaft wear, which I believe is the result of these higher temperatures. I think these cars benefit significantly from "restoring" the oil cooler in the radiator. Using the oil coller in the radiator and the oil cooler under the radiator, in tandem is the very best of both worlds. We have done this to several vehicles, with great results. We have made up hose kits to accomplish this, also.

Windage is a problem in these engines. Lately, we have been using the "early" oil pick-up and screen in our engines. We combine this with a pan spacer and our windage trays. This seems to help keep the crankshaft from picking up oil from the oil sump and whipping it into suspension.

Stock crank drilling has been an issue and this has been addressed and discussed at length. This seems to only be an issue in very high rpm use (above 6,500 rpms.)

Needless to say, the "oil problem" is complex and requires more than one "fix" to completely cure. The solutions are variable, according to the intended use and how the vehicle is driven. There are people that have been successful by using a high quality oil and then driving very conservatively, in terms of rpms and loading. There are others that could blow up an engine, every weekend, without major changes being done. These people could break a crow-bar in a sand box.

I'm trying to help them all.

Tony

Driving like a pu$$y....

Tony

Fixed it for ya...

worf928

I'm aware of the programmable variety ...
... used by Porsche etc. I wasn't suggesting that we need an engine dyno that can simulate the Nordschleife or Laguna Seca.

The ability to rotate the motor by hand 20 to 40 degrees about the roll axis would go a long way towards being able to see what happens to the motor under G. If you skip the programmable part the rest is all mechanical. Perhaps, still, to difficult though.

worf928

To give folks a better context on what you're doing/developing - a 928 motor that can be raced weekend after weekend for many, many weeks - what is the typical operating lifetime of a Porsche Motorsports race motor?

Say, if someone bought a new Cup car, how many hours of track use would they get out of it before it needed a tear down? And how many zeros are on the right side of the number on the bill?

MattCarp

I suppose the design was limited by the technology of the 928 era. Makes me wonder how the thing worked at all. then again, I know the answer - I don't drive hard enough!

Maybe the Panameras have it all worked out...

James Bailey

The reason why Porsche used a V-8 was that it need not spin high RPM to make the power that they wanted, remember at that time the 911 was a 2.7 liter and torque was very limited. And that damn cooling fan made so much noise

jcorenman

Greg, Great post!! Thank you

soontobered84

Greg,
I have both the cam covers and the intake off my '94 GTS for mechanical as well as aesthetic issues. I would prefer to not have remove either one any time soon, but is there anything I should do prior to reassembly that would head me in a direction toward solving the oiling issue before the full blown "fix" is revealed, if, in fact, it ever is revealed? In effect, I guess I'm asking should I add the other vent to the cam cover in lieu of the plug, or should I remove one of the vents and replace with a plug?
Thanks for all your help,

IcemanG17

EXCELLENT answer....this single post provides the best info on the 928's oiling issues all in one page.....time to put this in the archives.....

While there IS quite a variance it how 928 racers manage to blow their engines...some can run stock systems forever (MK), others blow stock and modified systems (everyone else), granted some faster than others.... The one thing I am 100% sure of is the 10 hour rule.....if the engine lasts longer than 10 hours on track...chances are it will go for a long time....you don't find many that last say 20 hours.....its 10ish or a long time......

Jadz928

I feel like a just finished stuffing my face at Thanksgiving dinner! ...I can't believe I read the whole thing!!
Well, 99% of it... skimming thru some Kibort anecdotal diatribes, and passing some Rennlist style negative "poundcake" served up way too close to the pumpkin pie (600hp, holy moly!), with real whipped cream. Yum Yum, Andy... you are gonna have some fun with this one!
Greg, what can I say? Amazed. Still processing.
Skipped wrenching on my own car today to enjoy this knowledge feast. Thanks!