T&T Racing

I believe unless specified, all Porsche 944 torque specs are dry except nuts on cylinder head studs which is a thin coating of oil.

Tiger03447

Good morning, Guys..I took my cover and the bearing inserts , new and old, along with the shaft to my machinist. The shaft was true and we are going to polish the journals on the shaft, as the front one had some wear on it. The interesting thing was that where Porsche punched in the part numbers on the back of the bearing shell, it raised the metal on the rear of the shell. This was not cleaned off and the extra metal shoved the shell over enough that it pinched the shaft on the opposite side of the bearing, causing the tolerance to be lost and the shaft to bind. Stoning ( a machine shop process- not what you are thinking..LOL) ) the back of the bearing shell looks like it will alleviate the problem, because it's only 1-2 thousandths of an inch that it is displaced. Hopefully this will alleviate this binding problem..I guess I won't know until the shaft is re-installed. I'll keep you posted as things progress. The new bearings have arrived and they will be polished on the backside of the shell prior to the install. Thanks. responses are welcome.

jeyjey

Yikes. So genuine Porsche bearings? That's pretty poor quality control....

PetePorsche

I've seen oem Porsche rod bearings that I wouldn't install on a wrecked engine.

Tiger03447

Yep..Porsche bearings..right out of the box. Hope this cures this situation. Fingers crossed.

tempest411

Remember they're made for them by Glyco. I've read their bearings for these engines are kinda crude, and were when these cars were new, hence the 'Michael Mount Bearing Mod' for the con-rods.

Tiger03447

Good evening guys..after further consultation with my machinist buddy, he informs me that although the journal surfaces are great, and true, there is a bout a 12-13 thousandths bend in the middle of the shaft. He also tells me that the hydraulic press that he has is not up to the job of bending the shaft true again. There appears to be listings for the 84 shafts and the 85 shafts in the PET. Nothing for the '83 cars. One company says that Porsche wants about 835.00 USD each for a new shaft. so I think I'll go with the straightening route first..So, since the upper shaft has slight tight spots, when I rotate it, I presume that it may be bent as well. We'll have to see how all this shakes out ...after I remove the intake manifold, ignition stuff, fuel injectors and associated wiring etc. Not a happy camper about all this..Grrrr.

Tiger03447

Tempest...Glyco = lowest bidder??

tempest411

I sure would love to hear from others on this, but I believe the balance shafts are interchangeable. The main difference in the early ones is that they did not have the plastic pieces attached to the counterweights that act as baffles to prevent windage and aeration of the oil. I'm sure if you called a shop like Lindsey's they'd be able to prove or disprove this. Of course you can always have yours straightened. If the shop where they're at now can't do it, I'm sure there are those around that specialize in this kind of thing...

StoogeMoe

That sounds like a lot, but how do you know that is still within specs? I mean, how would they get bent that small amount? That's probably the way they were from the beginning. If it still bothers you, you should be able to find some on EBay for cheap. I think I even have 4 spare ones.

Tiger03447

Thanks guys for the input. Highly appreciated. I might be in the market for another one, or two.. I want to pull the upper one before going further. If it's bent too, that may just mean that it was OK by Porsche QC. Perhaps someone on here has a way to access Porsche drawings and specs? But it seems strange to me, that if the shaft is bent, then the bearing surfaces, although good within themselves, would not be parallel, as the shaft would be in somewhat of an arc. This, IMHO, would produce a lot of bearing wear on the bearing surfaces, and would make it more prone to binding and increasing internal friction within the engine itself.. If this were the norm, it baffles me as to how Porsche would let this get out onto the production line, but, if they were produced by an outside vendor, then they would probably be checked sporadically by the QC dept, say 1 or 2 shafts per hundred and the defect would go unnoticed. Also, maybe these aren't the original shafts, or were damaged by a PO? Anyway, it's good to know. I'll keep you posted as to how things progress. Thanks.

jeyjey

Your argument is predicated on a bent/not-bent state, when in engineering terms there's no such thing: there's only how-bent (or more generally how-straight).

So the question is really "how much wear/binding will a +/- 13 thou result in?" (I haven't a clue; I'm just saying that's the question that needs to be answered.)

jeyjey

While Porsche doesn't give a runout spec for the balance shafts, they do give 0.02mm for the camshaft. That's less than 1 thou, suggesting a 12 - 13 thou bend is pretty dang bent.

Tiger03447

I agree, Jeyjey. If I can get it straightened to about 1-2 thousandths that would probably be straight enough. I may have to send this out to a crankshaft shop to do this. They straighten some pretty bent cranks to more than acceptable limits. If I can just get the front and rear bearings to run parallel within that amount of tolerance, that would be good enough for me.

Gage

Tiger, you're over thinking this. The balance shafts are high tolerance parts with only two bearing points (very different from a cam or crankshaft). The machining (and straightness) of the central part of the shaft will have no appreciable consequence on the journal to bearing tolerance. In fact, an attempt to straighten the center may very well create an out of parallel condition within the journal surfaces.