rough crank shaft

I finally split the case and was able to remove and clean everything. The bearings were in quite good shape but I will replace them anyhow.

I did, however, notice that the crankshaft was rough and looked amost unfinnished. Not the bearings but the darker metal that is shaped in a pie type shape. The edges are rough and eroded, is there a reason for this?

I wish I could post a picture.

Adam Roseneck

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1978 911SC 3.0
roseneck@cyberbeach.net

Congratulations on reaching the milestone of complete disassembly! I have not done a Porsche engine yet, but I've done many others. Without any question, you are absolutely right to replace all your main & rod bearings after they have been disassembled. No questions asked. Even if they look new. Have you decided what studs and rod bolts you are going to use? I'd be interested in what you decided on that, and why. Raceware? OEM? ARP? Other?
As to the crank, the only surfaces that would normally be polished are the bearing surfaces where at the main bearing journals and rod bearing journals. Crankshafts are first cast, and are then ground and polished at the journals. If its not a bearing surface, it doesn't need to be smooth or shinny. Those other places look porous because of the casting process. However, the entire crank certainly has to be balanced. Therefore, you might see places where it looks like its gouged or cut; assuming you find something like that on your engine's crank, and it wasn't a failure that prompted the overhaul, that's normal. I assume that you are planning to send that guy off to a quality engine builder or machine shop to have it tested & polished before reinstallation - right? I can't wait to open mine up. Best of luck with it.

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Steve
'89 C4

Are you sure it's not just crusty carbon buil-up from infrequent oil changes? I haven't seen that before but I sure wish you could post a pic. If it is pitted you should have a machinist magna-flux it and inspect/rebalance it. Since the bearings looked great you should only need to polish the cranks bearing surfaces so long as it passes the other inspection.

You'll need to have a machinist polish the crank anyway so have him give his opinion at that time.

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Tyson Schmidt
72 911 Cabriolet

Just read the above reply. For clarification, 911 crankshafts are not rough or porous at all. It should be smooth on all surfaces. They are not cast but rather forged. If any of the surfaces are rough or porous it is either from corrosion/rust/acidity damage or from foreign material build-up. I hope for Adams sake it is the latter.

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Tyson Schmidt
72 911 Cabriolet

I have a camera but the quality is so poor what you wouldn't know what you are looking at. To be honest, it looks like acid ate away at the crank shaft. Not on the bearing sections, they look great, more on the dark pie shaped pieces that hang off the crank.

I'm going to have a top notch Porsche specific machine shop up her in Canada take a look at her and tell me whats up. They're about 350 mi away though so it might be some time until I can get around to it.

Is there any way that I should be storing the shaft so I don't screw it up. At the moment its standing on end on a towel (my mom will kill me).

BTW, everything else looks perfect in the case except for that rough area... damn its bothering me

Adam Roseneck

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1978 911SC 3.0
roseneck@cyberbeach.net

Definately hard to know what you're talking about w/o seeing a pic... but I'm pretty sure that you are looking at the semi-rough texture of the counterweights. Should be ok...the counterweights aren't machined so they are still roughly forged and should have a slight texture to them.

I'll post a picture in a bit.

Here:

Also, it seems that I have heard people say that you should store crankshafts standing up on their end. To keep them from warping or something.


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Leland Pate

___79 SC Targa

[This message has been edited by Leland Pate (edited 03-22-2001).]

Adam,

If you're planning on replacing the flywheel (might as well since it seems you're going all-out on the motor), you can use the old one as a "stand" for a little more stability. Hate to see the crank get knocked over and dinged up.


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Kevin
87 Carrera

Hello

Your crank musst be messured, fluxed and maybe polished anyway. Your rods have to be aligned and get new bushings. Just ask a local engine rebuilder for assistance.

The best is to grease or wax the parts and wrao them in towels. After that you wrap it in plastkbags to avoid getting to much humidty or wetness onto. Best is storing in an hard box. A falling crank needs some additional work.

Grüsse

Thanks guys, I wish there was a local guy here whos brains I could pick...

Adam Roseneck

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1978 911SC 3.0
roseneck@cyberbeach.net

3.0 cranks go thru a factory surface hardening process called tufftriding (sp?), they usually survive situations that would kill lesser cranks. from the pic yours looks good, but you need to have a machine shop polish it and mic it, to be sure. if you need to grind it undersize, it should be rehardened, and in that case the whole job should be done by a shop experienced in porsche crank repair.