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I didn’t think a car dealer would stock that thanks. I’m going to bring the crankshaft to the machine shop hopefully they know how to drill a hole and put a fuse plug on it. If not I will attempt to do it myself
On a 928 crank, all that should be needed is a "buff" with a scotch-brite style belt.
If the machine shop wants to polish the crankshaft with a belt that has sandpaper on it (even 1500 grit), be concerned.
The following gets complex: (I've posted this information multiple times. I'm not sure anyone understood it. Each time I try to simplify this more. Hopefully this is understandable.)
Most all 928 crankshafts started life with "red" sized journals and used "red" sized bearings. (Largest journals and bearings with the most amount of clearance.)
Porsche originally furnished bearings in the three different journal sizes....blue (smallest size), yellow (middle of the range size), and red (largest size). Each bearing shell varied .005mm, from the proceeding "color". The original replacement part numbers had the normal 11 digit part number, followed by 001, 002, or 003 to designate what bearing size you needed. However, since Porsche never "bothered" to explain this....and the marked "colors" on the crankshaft journals "washed off" in very few miles, these part number confused everyone.....unless you happened to work in the engine assembly area....or worked on race engines, where this information was well known.
So, to eliminate the confusion, Porsche changed all the part numbers and always sent (to this day, from the "street" department) 2 yellow bearings in the same box (middle of the size range or a blue bearing combined with a red bearing in the same box (which "averaged" out to have the same clearance as 2 yellows.)
The "middle size bearing sets" worked on either blue, yellow, or red journals....sort of. It was not optimum bearing clearance, but not enough to cause bearing failures. "Blue" cranks would have .004mm more rod bearing clearance and "red" crankshafts would have .004mm less oil clearance. Either combination would run and function.
The "issue" was with the Glyco replacement rod bearing sets (in the past). In the beginning, Glyco assumed that the crank journals would all wear to some extent, so they "did the people a favor" and sent replacement bearing sets that were very tight....sometimes tighter than the original blue bearings.
Well, since 928 crankshafts did not wear (or wore tiny, tiny amounts) and most of the crankshafts had "red" journals originally...this radically reduced the oil clearance.....and many engines failed from not enough rod bearing clearance. (Look at the factory bearing clearance specifications, and do the math.)
It now appears that Glyco has figured this out...and now supplies rod bearing sets that have a greater amount of clearance ("red" sized). Hopefully, this continues.
You still have to measure and check clearances, however. (Say you have an original crankshaft that had "blue" journals...and you install a set of "red" bearings. The oil clearance is going to be....pretty large.)
Now I am debating on not taking it to a machinist lol.
You need a high quality machinist....that person is very important to your success.
Before any work is done, have everything measured and compared to the specifications in the WSM.
Make decisions from there.
Can not overstate the need to have the crankshaft cleaning done, as reminded above. That means drilling out the plugs, cleaning the grit and slime out, then tapping for new threaded plugs. Think about this need as you shop for a good service.
Can not overstate the need to have the crankshaft cleaning done, as reminded above. That means drilling out the plugs, cleaning the grit and slime out, then tapping for new threaded plugs. Think about this need as you shop for a good service.
One of the most important parts of rebuilding the engine is cleaning the crankshaft.
My "regular" machine shop doesn't like to do this job. I take my crankshafts to the people that build my new crankshafts. They hate doing this...and generally hand this job to the "rookie" to do (but I don't pay "rookie" labor rates to get this done.). Over 50% of the time, the job is not done correctly. I've had remnants of the old plugs pushed down into the oil galley (more than once), completely blocking oil flow to a rod bearing (twice.) Last time the "rookie" drilled the holes in the crankshaft too big for the thread of the plugs and 1/2 of the tapped hole had zero threads. This would have leaked oil past the plug like a fire hose.
My point is:
No matter who I ask to do things, these days, I have to be extremely vigilant in my inspection process to guarantee a high quality product.
This is very difficult, requires a considerable amount of time, and requires a considerable amount of experience to "catch" the errors.
Whenever I see someone that has rebuilt some mechanical part of a 928 and is successful (success can not judged immediately....tell me how the thing you "rebuilt" is functioning in 5,000 or 10,000 miles), I'm really happy for that individual.
These are not simple engines and transmissions to rebuild!
H
I took the crankshaft to a machine shop. Before I called someone verified on the phone they would work on the 928 so crankshaft. He said he would clean and polish it also drill out the holes to remove the sludge. So I drove over an hour in a tundra that does nothing but waste gas to bring it their. Then they said they would not drill it and the crankshaft had to be grinded.
So I removed the crankshaft from the counter and its back on my backseat again. I called another place that is 4 hours away and they told me to call Jake's crank shop (I think it was jakes) . The guy said he can do the work but its going to be expensive. What stood out with him was he asked what colors the bearings are.
I'm going to spray some wd40 on it and wipe it with a cloth
I'm not sure I want to know the story, on this engine. I know one thing...it's going to take a lot of WD-40 and a few years of wiping to help that crankshaft.
My suggestion: Toss that crankshaft in the trash.
Buy a used standard/standard crankshaft.
I've got several of them, if you can't find one that makes you happy.
(Although the one that Mark Anderson referenced above, looks pretty nice!)
09-29-2020, 09:31 PM
