964 Engine Rebuild - rings bearings questions - Page 2

AVI_8 · 07-30-2016, 10:08 AM

Quote:

Originally Posted by toddu

What causes pitting on a cam like that?

Todd

Too little ZDDB (Zinc) in modern oils from what I've read, you can buy oil from a specialist supplier with a higher ZDDB content

mikedsilva · 07-31-2016, 02:19 AM

Quote:

Originally Posted by Sboxin

I would open up the case and rebuild the bottom end - - since you are already this far along.
Because of the damaged cams, you may find damaged bearings also.
You have already done the hard work on this engine . . .

We found this in our engine . . . #5 rod bearing damage - either bad/low oil or run too hot . . .
And, the intermediate shaft bearings needed replacement . . . so rods, crank, and flywheel off to machine shop for refurbish and balancing - well worth the low cost . . .

Regards,

Well I took your advice, and decided to split the case.
Again, being new at this, I wasn't sure what to expect.. I think my main bearings looked mostly fine.
I decided to remove the rods and found very fine scratches.. my fingernail did not get caught in the scratch... but all will be replaced regardless.

mikedsilva · 07-31-2016, 02:20 AM

first split

mikedsilva · 07-31-2016, 02:20 AM

crank

mikedsilva · 07-31-2016, 02:23 AM

There is 1 tiny scratch on one of the crank bearing surfaces.. I can get my nail to catch in it.. Shold I get the crank polished?
Inside the case was very clean.. only debris was from me removing the head studs (locite bits) and splitting the case.. (a bit of gasket cement flaked off)

mikedsilva · 07-31-2016, 02:24 AM

mikedsilva · 07-31-2016, 02:25 AM

mikedsilva · 07-31-2016, 02:26 AM

Case got a clean

mikedsilva · 07-31-2016, 02:27 AM

mikedsilva · 07-31-2016, 02:27 AM

mikedsilva · 07-31-2016, 02:28 AM

RedCoupe · 07-31-2016, 07:49 AM

I see a couple of issues here. The scratches look like debris contamination to me, while one bearing shell shows shows some wear that could have been caused by a breakdown in the oil film. I've seen that in engines that were lugged excessively, but I suppose that there are other hard use conditions that can cause this.

Sboxin · Sboxin's Garage

" Shold I get the crank polished? "

Mike,
Good work on your engine !

Yes, while the crank and rods are out you should find the best machine shop in town and have them refurbish the crank (polish) and the rods - and balance the whole rotating mass . . . crank, rods, and flywheel. Porsche does excellent work on the original parts and very little improvement may be seen in a second balancing job - but at least you know it will be close to perfect when you put it back together.

A question: what oil have you been using ??
We use Amsoil Race oil 15-50 that has a high zinc content - but it is a race engine with no Cats to worry about. And, we get an oil analysis done with every oil change . . .

Regards,

mikedsilva · 07-31-2016, 11:19 AM

Quote:

Originally Posted by Sboxin

" Shold I get the crank polished? "

Mike,
Good work on your engine !

Yes, while the crank and rods are out you should find the best machine shop in town and have them refurbish the crank (polish) and the rods - and balance the whole rotating mass . . . crank, rods, and flywheel. Porsche does excellent work on the original parts and very little improvement may be seen in a second balancing job - but at least you know it will be close to perfect when you put it back together.

A question: what oil have you been using ??
We use Amsoil Race oil 15-50 that has a high zinc content - but it is a race engine with no Cats to worry about. And, we get an oil analysis done with every oil change . . .

Regards,

Roy
I have only had the car a year, and travelled 2000 kilometres in that time.. I have been using a locally produced oil... HPR 30 20W-60 (Mineral)
It claims to have zinc 1600 ppm.

Before me, well, I just don't know that they used and hence why I am doing this. Pretty sure the car was rarely used though.

Sboxin · Sboxin's Garage

Quote:

Originally Posted by mikedsilva

Roy
I have only had the car a year, and travelled 2000 kilometres in that time.. I have been using a locally produced oil... HPR 30 20W-60 (Mineral)
It claims to have zinc 1600 ppm.

Before me, well, I just don't know that they used and hence why I am doing this. Pretty sure the car was rarely used though.

That Penrite oil looks like a very good oil . . . cam damage was probably done before you got the car anyway . . .

Good luck with the rebuild,

Regards,

mikedsilva · 08-11-2016, 03:06 PM

Update
My cams and followers have been sent to John Dougherty in the USA for regrinding.. upon consulting one of the more reputable Porsche shops here, they claimed that there wasn't anyone in Aus doing a good enough job and that it wasn't worth risking.

Still not sure on changing the profile though... at this stage I have told John to keep it stock...