Crank PN and page 204

Zeke · 09-03-2005, 05:52 PM

Just did a pretty good search only to find nothing about crankshaft PNs. I guess the 901.xxx.xxx.xx no. is not anywhere one can see it, if at all. What is that number that is on the outside of the counterweight?

Also, could someone check page 204 in the engine book and look at the numbers for the various rod bearing sizes for the 2.4-2.7 crank? This is down a ways on the page where the .25mm to 1mm bearings are listed. It doesn't jive.

I ask because I'm crank shopping and have looked at one that the rod journals measure all fairly close to 51.84, out of spec. I assume this is safe to use for a grind to 1st stage (something I will try to avoid pending finding something in spec). But it would help to know if one I find has already been taken down and where it fits in the range. I suppose I could just subtract, but I would like to see the range of allowable tolerance for each stage.

The one I saw has an R stamped on the same counter weight as the factory number and I assumed that meant "rebuilt." But, it's still above the range of the first cut, as far as I could tell. The mains measured 56.84, so I passed because they too were out of spec. It's strange to me that the both came out to "xx.84" after the conversion of x25.4. I measured them 3-4 times and in differnent places. No more than .001" diff anywhere.

Help the noob. This stuff is not in the book that I could find. TIA.

davidppp · 09-04-2005, 12:14 AM

Hello Zeke.

Got to ask the silly question first..do you have slip guages etc to check your Mic for accuracy?

Its prctically impossible to have journals worn 6 thou stay round and not scored..

Leastways, I've never seen it.

Some race engine builders do deliberately increase clearances by hard polishing, or even a tiny grind..

Kind regards
David

Zeke · 10:44 AM

David, no, I don't and the only way for me to check the instruments is too compare them, i.e., use an inside mic and a caliper, etc. If they all read the same, at this point, that should be good enough for shopping, don't you think? And AFA OOR, they could be a bit. I tried to check at different angles around the journals, but I'm not the machinst, just the buyer, I'm only trying to get a good crank, I'm not assembling anything at this point.

I think I would tend to rely on Plasti-gauge and proper torque once I get there. Meanwhile, I just need to cull out the junk. You know, all that stuff laying on the ground at the swap meet. There's a reason that the stuff is out there, and it's not always because a seller wants to do anyone a favor.

EDIT: I did do what I said and checked the mics. The one I was using on the journals, a 2"er (I have 2 of them), had slipped out of calibration. Now I'm back in business and the crank I measured is in spec after all. It's 51.99. Thanks for the heads up, David.

Still don't know about the numbers on it and the specs in the book. They look to be misplaced from another column, but I didnt' see that on the corrections page at the top of this forum.

Zeke · 09-09-2005, 08:53 AM

No one on the book? How 'bout the PNs on the crank? I now have one that is claimed to be a 2.4S crank. I can't tell the difference from the T crank. Both counterweighted as they should be. Early 2.0 S cranks were different, I think. PET says "nitrated."

What about PNs on cams? Are they visable? I get to go thru a pile of about 50 cams to see if there is anything I want before they go with with the rest of the stockpile to auction.

Zeke · 09-12-2005, 07:33 PM

Someone tell me I'm all screwed up then. I mean damn, I sit here for all weekend and no one knows anything about crank sizes. I thought this was an engine rebuilding forum. If I'm just plain stupid and not seeing something, sombody set me straight. Please.

I just don't see how you can put a 56mm bearing on a 52mm journal. If it's a misprint, I'd like to know what the correct numbers are. I'm not going to assume that just one digit is off on each line, I would like to see the whole number to the hundredth of a mm.

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by Zeke
No one on the book? How 'bout the PNs on the crank? I now have one that is claimed to be a 2.4S crank. I can't tell the difference from the T crank. Both counterweighted as they should be. Early 2.0 S cranks were different, I think. PET says "nitrated."

What about PNs on cams? Are they visable? I get to go thru a pile of about 50 cams to see if there is anything I want before they go with with the rest of the stockpile to auction.

According to the Porsche spec books, all of the 2.4 and 2.7 crankshafts are the same. The 'S' crank should have been treated identical to the 'T' crank in terms of the hardening process.

The numbers stamped on the camshafts are somewhat useless, as they have often been reground to something else. You can always easily have a camshaft reground, so what you really need to look for is a good core. The part numbers on the cams are incomplete - they are missing three of the inside numbers...

-Wayne

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by Zeke
Someone tell me I'm all screwed up then. I mean damn, I sit here for all weekend and no one knows anything about crank sizes. I thought this was an engine rebuilding forum. If I'm just plain stupid and not seeing something, sombody set me straight. Please.

I just don't see how you can put a 56mm bearing on a 52mm journal. If it's a misprint, I'd like to know what the correct numbers are. I'm not going to assume that just one digit is off on each line, I would like to see the whole number to the hundredth of a mm.

Everyone was at the German AutoFest this weekend. I did review the information in the book, and you are correct - those numbers in the table are not correct. I have since added that correction to the corrections page for the book:

http://www.101projects.com/911-Rebuild/corrections.htm

-Wayne

Wayne 962 · Wayne 962's Garage

Quote:

Originally posted by Zeke
EDIT: I did do what I said and checked the mics. The one I was using on the journals, a 2"er (I have 2 of them), had slipped out of calibration. Now I'm back in business and the crank I measured is in spec after all. It's 51.99. Thanks for the heads up, David.

51.990 would be a perfect crank, ground that way from the factory. If all six journals are reading that number, then the crank is very good, and would appear to have almost no wear on it.

Then again, if your gauge only reads XX.XX, you might need a better measuring tool. But, if it's showing 51.99, then you're probably very close.

-Wayne