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Walt Fricke's Avatar
 
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Well, I am confused here. For 911 applications, you install the head studs based on how far they protrude above the case. 135mm comes to mind. If you screw them in until they bottom, you don't have full thread engagement with the thick washer and nut assembly on the head. If you don't screw them in deep enough, the hex key gets pushed out of the end of the barrel nut (assuming you don't switch to reduced size regular nuts of some sort, which is a better mousetrap anyway). So head studs aren't going to bottom on our cars if properly installed, and this should be a non-issue.

With the mag cases, one way to avoid case savers (which may be the better mousetrap anyway, so why avoid them) is to drill and tap the head stud holes in the case deeper, and then use a longer head stud. Distortions caused by bottoming were never discussed by Bruce Anderson or other gurus back when this was a common issue, like in the 1980s.

Then there is the curious matter of ARP making the threaded part much longer on the flat end, and shorter on the domed end. That seems backward. On the other hand, I suspect their design engineers didn't have hands on experience with assembling 911 motors, and a tiny benefit - like the washers and nuts dropping into place better, like round end wheel studs and NASCAR pit stops - isn't likely to have occurred to them. Fact is you can use a magnet to deal with these issues, so they are a minor inconvenience. When I bought head studs, I bought the Supertecs, and would do it again even though the ARPs seem just fine too.

When head bolts on Detroit V8s are replaced with studs, is the normal procedure to screw the studs in until they bottom? If so, the doming makes more sense there. It is hardly intuitive that the extra loading caused by bottoming and then torqueing some more places on the system will have any effect at all. But then again I didn't see how preloading (torqueing, stretching) rod bolts would change the rod bore ovality, but guys who had measured such things wrote in to show from their measurements that it did. Additionally, won't the tip of the drill used to drill stud holes leave a conical end shape in the case? The stud ends are round, so you will get a circular line of compression on the case when bottoming. How is this different than what happens when a flat end stud is bottomed - still a circular line of compression?

Anyway, I'm not worried about the orientation of the ARP head studs in one of my motors, and if I had occasion to remove them (unlikely, as the aluminum cases don't seem to need the machining the mag cases do) I think I'd put them back in the same way - dome up. After 150 or so race hours the main bearings (Glyco) looked like they were good for another 150 - no worn high spot. If you don't bottom, what possible problem can orientation cause?


Last edited by Walt Fricke; 01-04-2017 at 12:06 PM..
Old 01-04-2017, 12:01 PM
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As Walt has pointed out-the studs are installed to a specific height. Though they could be installed
with the domed end down it makes very little sense engineering wise. It is understood that bottoming the studs in the case could create issues if over tightened I have never experienced that
after many installations-but I don't torque them into the case either-just get them to the correct
height. It also is more prudent to install the maximum number of threads into the Al or Mag
end. If one uses the shorter end there is much more risk of a pullout. Standard practice steel
to steel is 1.5 time dia. engagement and in a soft cast metal more is obviously required.
Can we get back to bearings now?
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Old 01-04-2017, 04:40 PM
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Speaking of bearings, what are you guys using for Crank Shaft?

Clevite Rod Bearings on Order :-)
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Old 01-04-2017, 05:03 PM
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The ARP head studs come with 12 point "Jet" nuts so having a round end sticking out seems like it makes sense. Good to know that the round end goes in.

As for Pelican having the Clevites, they are listed but once you add them to your cart it says out of stock. I think I will be calling Supertec.

The main bearings I have for my 3.2 rebuild are Glyco, made in Poland. I need to get some more Plastigage to check bearing clearance.

Last edited by rs-vic; 01-05-2017 at 10:30 PM..
Old 01-04-2017, 05:29 PM
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Quote:
Originally Posted by henry schmidt View Post
we carry most sizes...
964 3.6?
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Old 01-04-2017, 05:52 PM
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This stud question should go over into its own thread and leave this one to the bearing issue. I am at fault here I guess, but I just answered a question.

Put the studs in way you like. Just that the radius end is done for the purpose stated.
Old 01-04-2017, 06:52 PM
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Not good.
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Old 01-04-2017, 08:18 PM
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Quote:
Originally Posted by porterdog View Post
964 3.6?
Yes, Standard and .25mm
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Old 01-05-2017, 08:15 AM
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964 3.6 is same rod bearing as the 3.2 Carrera and 3.3 930. 930-103-147-15 for STD size
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Old 01-05-2017, 08:15 AM
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This is unfortunate. My engine is built (have not started it yet) but I recall seeing my bearings look the same as the ones in the pictures after test fitting the rods. I thought it was odd but didn't do anything about it. The rod was not seized after torquing. The "Rod drop test" after installing with assembly line and torquing appeared to be consistent across rods. Anyone think it's going to self destruct/spin a bearing on start up?
Old 01-07-2017, 10:29 PM
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With no gross binding, I'd not suppose you'd get instant self destruction. The problem might be more of a much shortened lifespan if the bearing sizing is as inconsistent as some have measured. And you have no way of knowing that now. Perhaps you know when you bought the bearings, and from whom, and have a box which shows where they were manufactured? It looks like South Africa is the place to worry more about. But if from Porsche, not so much.

My problem with Glycos had to do with bearing strength - I had a motor blow up on the chassis dyno with less than an hour, all on a dyno or idling, on it. Wasn't from bearings, but the disassembly revealed a bearing surface pattern associated (so the books and articles say) with inadequate strength. Hence my resolution to go with Clevite, since nowadays you can get them in Porsche sizes and don't have to undercut the crank and use special rods and whatnot. Of course, spinning the motor to 8,000 rpm does stress it more than the 6,700 or so you might occasionally see on a street motor.
Old 01-08-2017, 03:07 PM
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The engine build has spanned a couple of years now and for some odd reason I still have the packaging for the crank and rod bearings in the garage. I will let you know what I have when I get home, but they were packaged in a red box with cardboard backing and were purchased through pelican. I actually had pelican replace my first set since they appeared to have an inconsistent coloring on the bearing surface (i wasn't sure why but I felt that it could've been a QC issue so I asked to replace them and they did with a similarly packaged set that were consistent on color across the bearing)Also, it's a street setup so I don't plan on running higher than 6500.
Old 01-08-2017, 09:06 PM
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Hi all.

Today I opened a box with Glyco bearings from poland date marked 03-15.
Everything in perfect condition, I measured a small conicity of 0.01 mm to the sides as it should be.
do not be afraid to buy them.




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Old 01-26-2017, 02:01 PM
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^^^, so you purchased from the Dealer or aftermarket store like Peilicans?
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Old 01-26-2017, 03:02 PM
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I buy them from a aftermarket store on ebay in germany.
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Old 01-27-2017, 06:50 AM
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General statement.
Before retirement I had significant exposure to engine manufacturers and today's quality systems. When they have a quality alert parts are usually 100% inspected. This never guarantees good parts but in the heat of battle it's the best that can be done.
This is all background that the reality is the questioned parts are then returned to the vendor where I suspect most are just individually packaged and sold at a mark up in the service market. Many manufactures do not have the equipment to inspect their product outside the actual manufacturing process.
Old 03-13-2017, 07:38 PM
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Bottom line, Caveat Emptor, for God Sakes verify measurements, if you went far as to spit the engine case or even replacing Rod Bearings.
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Old 03-13-2017, 10:49 PM
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So, reading a lot of these threads, it seems that the problem with the Glyco bearings is dimensional - there are inconsistent and out of spec thicknesses from one part of the bearing to another and from bearing to bearing within the same batch. The inconsistencies would cause a condition whereby the bearing is too tight to the crank in spots, not allowing a layer of oil to remain between the bearing and the crank and causing metal to metal contact.

Presumably the problem isn't metallurgical, since the bearing itself is only designed as a sacrificial surface - i.e. the only times the actual metal of the bearing would come into play would be if:
a) a foreign object got into the oil, in which case the soft metal is supposed to allow the object to embed into the bearing rather than scratch the crank; or
b) the engine is starved of oil, in which case the thin film of oil separating the crank from the bearing would be eliminated, causing metal to metal contact (in which case it might offer brief protection to the crank before the bearing spun, but in the end it wouldn't matter what the bearing was made of since the damage would be done very quickly).

If I understand this correctly, would plastigaging the rods show whether there is a problem or not?
Old 03-14-2017, 10:19 AM
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plastigaging is ok for final check, but if they are inconsistent you may not see the problem, you need to measure the bearing and crank too be sure.

Quinlan, I see you are from UK, I think the problem with the glyco is only in US where they sold the glyco from S. africa. I never see theese in europe.

Daugaard
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Old 03-14-2017, 02:10 PM
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Damn.... I'm thinking I should tear down my finished 3.0 engine to the shortblock and replace the rod bearings.

I take it pelican only relies on it's suppliers to do QC.

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Last edited by Mark Henry; 03-19-2017 at 01:40 PM..
Old 03-19-2017, 01:37 PM
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