964 Crankshaft pits?

[Sboxin]

What is the future damage if I put this crankshaft back into our 3.6/3.8L rebuild??


It has been polished, magnafluxed OK and measured no wear.

Thanks for your feedback.

Regards,

[BURN-BROS]

It may be a hardchromed repair. Does the color of that journal differ from the rest?

[Sboxin]

Originally Posted by BURN-BROS

It may be a hardchromed repair. Does the color of that journal differ from the rest?

Aaron,
Thank you for your reply.

The first photo is #2 Rod journal---have you seen this on Porsche crankshafts before??

This is an original crankshaft - There was bearing wear on #5 that we assume was due to overheating/low oil/poor maintenance. I bought the engine with very little documentation expecting to rebuild for our race car.

The crank has been polished and magnafluxed.

These are photos of the crankshaft before polishing --- all but number 5 look normal.



This is the #5 journal where we observed the most bearing wear - the others looked very minor/normal.




Regards,

[BURN-BROS]

The 2/5 throws are the first to go when there is an oil issue.

A typical repair is welding the journal, which you would see the evidence of the weld outside of the vertical walls that control endplay of the rod.

Some repair shop may weld a journal where the weld stops where you are seeing the pitting but I have not seen one come thru my shop.

A hardchromed repair looks brighter than the rest of the journals with the pits you have posted. hardchormed cranks suffer from failure due to crack propagation @ the repair.


bottom line is you have a questionable crank and I would find another for your application.

[Sboxin]

Aaron,

Thanks for your help, we will stop here and think about our options.

Regards,

[BURN-BROS]

Your other option is to regrind your crank for a 3.0 SC journals and run a 127.8mm SC length stock rods or Carrillo rods. but you will need custom pistons for compression height and pin diameter.

This would be a good way to go IF grinding will go past the repair into uncompromised metal. It is a possibility if the crank was hardchromed. welding would penetrate deeper.

Other possibility would be Chevy journal diameters but Custom rods would be needed.

[Porshaah]

It 's difficult judging from the photo but I believe it's safe to install. I had a crank that looked worse, in that the scratches were solid lines. Your's appears to be a series of pits and also, do not go all the way around the journal. The machinest who checked my crank (i.e. who only works on cranks and cams - for probably the last 30 to 40 years) said, if it wasn't cracked it would have been good to install. If the scratches are parallel to the journal then there's a concern as that would provide a path for the oil to escape and affect pressure.

[Sboxin]

Originally Posted by Porshaah

It 's difficult judging from the photo but I believe it's safe to install. I had a crank that looked worse, in that the scratches were solid lines. Your's appears to be a series of pits and also, do not go all the way around the journal. The machinest who checked my crank (i.e. who only works on cranks and cams - for probably the last 30 to 40 years) said, if it wasn't cracked it would have been good to install. If the scratches are parallel to the journal then there's a concern as that would provide a path for the oil to escape and affect pressure.

Porshaah - Thanks for the feedback! We have similar comments from an experienced engine builder...still thinking about this crank and the rebuild.

I am wondering how difficult it is to find an acceptable used 964 crankshaft?? I'm thinking this may be impossible.

We have been advised NOT to grind the crank to put in oversize bearings. We have everything else done to begin assembly of this 3.6 increased to 3.8 with 102MM reconditioned cylinders and JE 12.5 CR pistons with Webcam 20/21 reground cams.

Steve Wong will dyno set the ECU for 245 RWHP and the best torque we can get - this is to stay in class with NASA PTA.

Regards,