924Board.org

[Carnut 280]

Alright. yesterday, went to second creek. had a blast tryin to keep up with a Mini Cooper S, (which killed me btw) and an 87 carrera, which I could out-corner, but he killed me on the straights.

ANYWAY, here is the real point. I've heard rumors that spun bearings happen from hard turns (I cant remember left or right) and that's cuz the oil is pulled away from the pickup, and it runs the number 2 bearing dry, which we all know is a bad thing. so to keep this from happening i've heard of a number of ways to stop it...such as cross drilling the crank, adding a dry-sump system, baffeling the oil pan, and just adding more oil.

Well, I'm too poor/cheap to do any of the above except adding more oil. so I did. I added about 1/4 quart above full before I took it on the track to avoid this evil problem. I took it on the track, all is well. I packed up, and went home. This mornin, I went out. and when I got back to the car, I rolled down the window, gave it a rev before lettin out the clutch for reverse, and I hear a clicking...so I start thinking to myself, "oh SH*T!" as it sounds EXACTLY like it did when I went on that road trip. I was about 15 miles from home this time (instead of 500). so I drove it home as carefully as possible, watching the oil pressure gauge like a hawk. luckily, oil pressure remained strong. so I got home, opened the hood, and it's loud. it's gotten much much louder than it was when I was out.

So...think I spun a bearing AGAIN calling for another rebuild? or is it just some other sound? And, if I did spin it again, should I fork out another grand or two, or should I just part it out, and ditch it in a junkyard? Thanks again everyone...gimme your best wishes...I could use em.
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Porschephile at home=Carnut 280

[78porsche924]

Damn that sux. Hope u didn't spin the bearing. Good luck whatever it is.
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90 944 S2
78 924 NA <---now sold and killed by new owner
snailshell trans
Bae turbo kit
to check out my 944 S2 http://www.cardomain.com/member_pages/view_page.pl?page_id=388139

[Paul]

I hope its just a valve lifter, but drain your oil and check for metal. If you have spun a bearing you will find metal in the oil.

[Carnut 280]

Yeah...Paul, I remember from last time it happened in OCTOBER! I'm soooo not happy right now....evil evil
(btw, i"m not bein an ass to anyone on purpose, sorry if it sounds ass-ish)
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Porschephile at home=Carnut 280

[Carnut 280]

so I'm sooo pissed off and angry at this thing, we've put about 7 grand into it, we got it for 3 grand. I"m thinking that i"m no longer gonna keep dumping money into it.

But, I love the way this car drives. It's a great car. the way people look at it, the neutral handeling, the ease of working on it, it's all great. I just don't know if it's worth it to put another $2,000.00 into a rebuild (it's an 'S' for all of you who did not know). what do you guys think? should I keep it? should I upgrade to a 951? I am soo pissed I dunno what to do.
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Porschephile at home=Carnut 280

[Lizard]

[-nick]

Huntley seems to have figured out the mystery. they posted this on a race list some time ago:

Huntley Racing had done a lot of research over the years into EXACTLY why 944 cars spin rod bearings. What we found out over several years of searching was that there is much more miss-information that actual facts. First we found that whether in a track car, streetcar or even a weekend show car all 944 based cars including the 968 can spin a rod bearing. Second this has nothing to do with HP or TQ. Third it has nothing to do with uncovering the oil pick-up (This is a common miss-conception promoted by many many shops). Forth is that extra oil, like a half quart over the dipstick, does nothing. Fifth the Accusump and other systems don't fix this issue (other possible problems yes, but not the common rod bearing failures). Sixth no matter how many baffles you have put in your pan they will not help. I can go on and on but to get to the 'meat' of the matter....

What causes rod-bearing failures is 99% of the time centrifugal force. We found the solution to the mystery in an uncommon place, the Chevy world. It turns out a Chevy motor has the same problem, the 454 big block. Chevy 454 big blocks, which were designed for lower RPM operation, later became popular for drag racers. The drag racers started to turn more and more rpm's in search of more HP, which resulted in a 'new' problem developing, spun rod bearings. It took years to figure out why. The reason turned out to be so basic that the likes of Chevy and Porsche simply 'missed' it.

As a crankshaft rotates it has many forces acting upon it. It is obvious that the pistons push on the rods, which push on the crank and so forth and so on. What was missed was centrifugal force acting on the oil within the crank. High-pressure oil is fed thru the center of the crank to the main and rod bearings. Oil passing thru each journal is forced out of the crank onto the surface of the bearing thru the oil feed, which is nothing more than a hole in the surface of the journal. Where the 'mistake' was made was in the placement of the hole. The single oil feed hole can be drilled at any point 360 deg around on the journal, this is a decision dictated during the production of the crank. When the 944 crank design was made there was no attention given to the placement of this hole and the effect centrifugal force might have on the oil within it. Where the feed was placed just so happens to be one nearly opposite the direction centrifugal force pulls the oil when the crank is in motion. As the RPMs increase the centrifugal force goes up, eventually to the point where the oil pumps pressure simply can't overcome it. When this happens the rod bearings are starved of oil. The reason more track cars have this failure is because they are at high RPMs more often and for longer periods of time. Also track cars tend to have relatively high oil temperatures which thins the oil and causes the oil pressure to drop which lowers the RPM point where oil starvation at the rod bearings occurs. Further the high RPMs and often overfilled oil pans (to supposedly save the rod bearings) cause high windage that aerates the oil, further reducing its lubricating potential. Older motors spin rod bearings more often than newer motors since they have had more high RPM time than new motors and they usually have less oil pressure. Baffles, Accusumps, overfilling etc... do nothing to stop this failure mode.

Cross-drilling came out several years ago as a remedy for this issue but not because the problem was understood but because the idea was that a second oil feed hole would add more oil. There was a positive benefit from crossdrilling. The new oil feed opposite the original oil feed was not either hurt or helped by centrifugal force due to its position. This meant
that the oil pump could generally keep up with the oiling needs of the rod bearings. Huntley Racing however took the cross-drilling to the next level and developed the Perp drilled crank. We perpendicularly bore a new feed into the rod journal, which is actually taking the nemesis, 'centrifugal force' and working with it to help to actually scavenge oil to the rod bearing as the RPMs go up!! Since we have machined cranks with this technique we have 'NEVER' had a rod bearing failure in any car, ever! We started offering these in 1998.

This subject and its relevance to the 944 world is obvious but it is only one of many possible failures, which can and do occur to these cars. Cars that suffer rod failure generally can trace this to the above mentioned rod bearing problem as the catalyst. Main bearings generally don’t have this problem simply because they are centrally located on the centerline of the crank and have a much smaller ‘arm’ to their outer diameter which makes them far less susceptible to oil starvation from centrifugal force.

So in summary if you have your crank out have the process done. If your motor is still together and you want to avoid spinning a bearing without the Perp drilled crank, keep your oil temps down, limit your RPMs a bit (look at your HP peak and avoid revving past it), run a higher viscosity oil, avoid over filling, and keep the oil fresh.

Derrek Huntley Khajavi
Huntley Racing

Copywrite (C) 01/27/2002

[Carnut 280]

good call, I've not yet determined completely the cause, but I'm 99% sure that it's a spun bearing.

The reason we didn't cross-drill the crank last time is because a respectable 944 racing team (and their shop) said that huntley racing is full of sh*t and that the company as a whole is crap. but, this is also the place we took the engine to for a timing belt tension, and they managed to put the idler pulley on backwards, thus if not caught, the timing belt would've been destroyed in 60 miles, and my valves woulda been bent. I think now, if we do decide to rebuild, I'll check out huntley.
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Porschephile at home=Carnut 280

[81turbo]

Cut your losses and get something else. Your frame is bent and you have 7K in the car. Rebuilding it again is not the smartest thing I have ever heard. Why not get a straight car and start there. Hell you could even get something fast.

[numbbers]

Carnut, first thing is to isolate which cylinder the click is coming from. That is done by pulling the plug wires one at a time. Yes, the noise from a spun bearing will go away when the cylinder is not firing. Valve noise will not go away. Even if it is a spun bearing, you do not need a full rebuild. Easiest way to fix it is to get a good used crank and rod from an engine that has crashed the valves. You can reuse your pistons and rings since you have so few miles on it. Also, you may consider just taking it back to the shop who did your rebuild. They may cover it.

Then, keep it off of the track!
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1980 924 Turbo

[78porsche924]

Or cross drill the crank and race that badboy.
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90 944 S2
78 924 NA <---now sold and killed by new owner
snailshell trans
Bae turbo kit
to check out my 944 S2 http://www.cardomain.com/member_pages/view_page.pl?page_id=388139

[924 turbo]

I'm not buying the oil starvation theory. There are plenty of people who have driven their 944s and 924S's considerably harder than your car is even capable of on racetracks, with slicks. If one of your rod bearings went, it's because of something else, like improper assembly or component failure. If I were you, I'd go after the assembler for a warranty repair.

If you can't get that, dump the car and start somewhere else. You've already put way too much money into a 924S, and more money isn't going to turn it into a 944 turbo. Start saving today.

And what the hell do you need two logins for? Your password works everywhere.
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Jon Furst

[jpab924]

Isolate the noise first before you condemn anything.

Numbbers has given you some good advice. Check this first. Jon is right, I don`t think you could have driven the car hard enough to spin a bearing. And if you did, you don`t have enough miles on it to have done it that quickly. I would say that is the rebuilders fault.

[Joes924Racer]

rebuild it bummer though.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[moone924]

Sucks man...

If it's true your frame is also bent, get a new car. Part it out, to regain some of the money.

There was a guy at my work with a '86 944 Turbo, that also had a spent rod bearing. High RPMs, drag racing and 44,000 miles added in it's death. The thing is, the car had lots of things added to it, racing clutch and flywheel, mass air, electronic boost control, chip, etc.
He sold it just a month ago for $2500, with two spare wheels with slicks. That's something you should spend your money on... there's deals to be had.
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Ryan Moone

Always shopping for a nice s2 931 to baby.
New philosophy : one car project at a time.