Christer

I don't know if anyone is really that interested, but my crank is now polished and found to be perfectly OK. Picture (and more to follow) at http://community.webshots.com/user/odegaard964 as usual.

Hopefully this week we can make good progress in putting the whole thing back together. I hope it is ready by the end of next week, I really do!

rutz964C4

Hi Christer

Very interesting pics.



ALEX

DaveK

Stupid question - what's the point of polishing a crank?

DaveK

I should probably point out - that was actually a serious question. Why does the crank get polished?

Can't help thinking you assumed I was taking the p*ss. Can't imagine why you would.

PCar SBA

The bearing journals of the crank get polished to get rid of minor wear marks. The need to have a mirror finish to allow the oil film to work. An engine that runs at operating temperature does not wear bearing surfaces at all since there is a film of oil between the metal surfaces. The wear occurs through dirty oil or film breakdown (knocking, stomping it when cold, etc.)

If the grooves or wear marks are too deep then regrinding is on the order together with undersized bearings (that are much more expensive) The rule of thumb is that when your findernail catches in the groove it is too deep for polishing. Of course a competend machine shop has better means to do this test.

Ingo

DavidI

Great pics, fascinating to see how it all comes apart.

Arjan B.

Christer..........

My 'advisor' for the Porsche says that only the intermediate bearings contain copper. The other crankshaft bearings are made from plain aluminuim.
Is this right?

Thanks for giving us the opportunity to look in to your engine. As you see you have good engine oil, a bright and clean engine inside. No sludge.

Pleae, a hounest answer...... was it technical really neccesairy to rebuilt it. Would your engine brake down in the near future?? What is the milage of your engine?

Thanks!

Christer

Dave, although I must admit it did cross my mind I came to the conclusion that it was a serious question. Unfortunately I didn't get round to answering this afternoon although my reply would have not has been as good as Ingo's.

Arjan, the car has done around 98500 miles and was using a bit of oil (you can see evidence of oil leaks), but not that much - maybe 1 litre every 1200miles or so. The thing is that it had started to get worse than before and it coincided with another decision. Do I want another car? When I first started to look around for a car 3 years ago, my budget was somewhat larger than what I spent on the 964. I couldn't find a car I liked more than the one I found (OK, so I didn't want sunroof but I think it would be hard to find one without aircon so I opted for the non-aircon car). I asked myself the same question early this year and I couldn't find a car that I wanted more than this one so I decided that since the oil consumption was getting worse that I would carry out a complete project to turn the car into what I think it should be. I am not changing anything cosmetically (well maybe cup mirrors but they are not a priority) other than the wheels and these are at least 5 spoke so will not look too radical. I don't want a car that is a show off, just something functional where everything is there for a reason. Weightloss is next but nothing extreme - probably just RS seats and rear seats out. I should be into 12xxkgs with half a tank of fuel by then as it is a low option car and currently weighs around the 1340kgs mark with the same fuel and all fluids.

Anyway, 9M tell me that the progress this week might not be so quick so I think I better book a flight down to Cornwall at this rate, as I was due to drive the car down at the end of next week. Am I gutted? Well yes, but I don't want a rushjob do I??

edit: Arjan, I don't know actually for sure on the bearings. I know the ones you mention are copper or copper alloy but I haven't seen the rest. I can ask if you would like confirmation?

Christer

Ingo, interestingly (or not as you prefer) I don't think we regrind cranks very often in the UK. 9M certainly don't. I was told in no uncertain terms that if the crank was not up to scratch then a new one would have to be used (or a used one which was in adequate condition). Either way, the cost would be relatively big.

ian c - u.k

christer ,
your pm box is full so i sent you email

Randall G.

Hey Christer,

After my rod bearing spun, I came to learn that there is vast difference in opinion between professionals with respect to repair/don't repair the crankshaft. So, I'm not surprised 9M is dead-set against it. Wayne Dempsey (author of "How to Rebuild and Modify Porsche 911 Engines") & Bruce Anderson both recommend against it, but then go on to describe how best to do it, if you must. Wayne, like 9M, recommends using a good used crankshaft, if at all possible, in lieu of repair.

I avoided the issue altogether when my rod bearing spun by installing the used 993 engine. I made the decision to go with the 993 engine without ever finding out if my crank was bad. As you suggest, a new (or even used) crankshaft is scary expensive.

BTW, if you're motivated enough, I would highly recommend a read of Wayne's book. It will really give you insight to what's going on with your engine rebuild, and why. Better yet, Wayne lays it all out in a logical and methodical manner, building from the ground up, if you will. Lots & lots of pictures, too. I have no intention of ever rebuilding my own engine, but found it a fascinating (and educational!) read, nonetheless.

Glad to hear your crankshaft came out okay....

graham_mitchell

Christer, great news about the crank. Looking forward to hearing that you've got her back!

Arjan B.

Christer, yes, I am interested in the made of the bearings. The way I ask is search for the high copper % in my lab test of my engine oil a way back. My advisor tol me that a possible new distributor drive wheel could cause that, and the bearings of the intermediate shaft. Now my oil tests are fine so far. No high copper % anymore since my last test in 2003.