964 Engine Rebuild - rings bearings questions

mikedsilva · 07-21-2016, 01:31 AM

OK
I am new at this but pretty deep into it.

my 964 90, had a few oil leaks... nothing major.. doesn't have the head gasket mod either (so I found out).
Mileage is only 90,000kms (not miles) and engine performs well, with good power, doesn't blow smoke, but has a few leaks from all major culprits.

I have pulled it apart with the intention of replacing through bolt o rings and cyl base gaskets, which are the apparent source of my other leaks.
Plan was to just have the heads machined and cleaned and re-seat valves as necessary.

My pistons and cylinders all look in good condition. No cracked rings.
Slight pitting on 1 cam and a fair bit more on the other.

Due to this, it makes me think I should split the case.. check for metal, and then perhaps replace bearings... which means 12 new conrod bolts and nuts too..

Question:
Is it acceptable to repair cams or are they now rubbish?

Can I use the glyco bearings for crank and rods from our Host or should I go genuine and pay through the nose?

Also, is it assumed to replace rings while motor is apart? If so, are Goetze sold by our host OK to use? There seem to be some negative press out there for this brand of ring.

Any advice appreciated...
Mike

RedCoupe · 07-21-2016, 05:33 AM

For sure I wouldn't reuse the cams the way they are. A regrind by a respected cam shop would be fine along with re grinding the rockers. My 150,000 mile cams in my 1990 had nowhere that amount of pitting, so I would be inclined to split the case and clean, inspect, and measure everything.

Mark Henry · 07-21-2016, 07:47 AM

Wow that cam is toast, are the journals pitted as well?

Looks like it had a hard life.

You say 90K kms, where are you located?

jdbunda · jdbunda's Garage

I just went through trying to figure out which bearings to use for my rebuild. Forum wisdom seems to be that the Glyco mains are generally fine, but the Glyco rod bearings (neither are made in Europe any more) have been considered suspect, due to several instances of new bearings being found to be out of spec. The bearings sourced from Porsche - which are apparently also sourced from Glyco - may have been at least been subject to some quality control and measurement, and therefore might be better. Several threads on this topic if you search.

mikedsilva · 07-21-2016, 11:20 AM

Quote:

Originally Posted by Mark Henry

Wow that cam is toast, are the journals pitted as well?

Looks like it had a hard life.

You say 90K kms, where are you located?

Australia

mikedsilva · 07-21-2016, 11:23 AM

Quote:

Originally Posted by RedCoupe

For sure I wouldn't reuse the cams the way they are. A regrind by a respected cam shop would be fine along with re grinding the rockers. My 150,000 mile cams in my 1990 had nowhere that amount of pitting, so I would be inclined to split the case and clean, inspect, and measure everything.

Thanks.
Yes, I will def split the case now and inspect bearings etc.
Didn't really want to split the case, but it seems counter productive not to do so.

The car has had very low use for long periods, and I'm told that can be one of the reasons to cause this...

Sboxin · Sboxin's Garage

We sent our 964 cams to Web Cam in California for refurbish and regrind to 20/21 higher torque
and, also sent rockers for refurbish - all excellent work and turn around time.

Web Cam Inc. - Performance and Racing Camshafts

Regards,

mikedsilva · 07-21-2016, 12:46 PM

Quote:

Originally Posted by Sboxin

We sent our 964 cams to Web Cam in California for refurbish and regrind to 20/21 higher torque
and, also sent rockers for refurbish - all excellent work and turn around time.

Web Cam Inc. - Performance and Racing Camshafts

Regards,

Thanks for that.. can I ask approx dollars for refurbing cams?
Also, I didn't realise that it's possible to re-profile for more torque... I see threads on the older engines using 964 cams for more performance...

Sboxin · Sboxin's Garage

Quote:

Originally Posted by mikedsilva

Thanks for that.. can I ask approx dollars for refurbing cams?
Also, I didn't realise that it's possible to re-profile for more torque... I see threads on the older engines using 964 cams for more performance...

Their web site shows $890 to refurbish ( "hard weld" ) and regrind . . .

We were looking for more torque to compete at the race start with the BMWs that generally have more torque than our Porsches with a same size engine. So far, the investment has paid off . . .

Short video of engine at idle . . .

Porsche 964 Cold Start Idle After Steve Wong Chip 11-25-2012 Video by Arizona-ed | Photobucket

Regards,

Sboxin · Sboxin's Garage

"Can I use the glyco bearings for crank and rods from our Host or should I go genuine and pay through the nose? "

Our engine builder uses Porsche rod bearings . . . yes, they are probably sourced from Glyco but at a higher spec. This bearing may be the most important part in the engine . . .

Regards,

toddu · 07-21-2016, 05:52 PM

What causes pitting on a cam like that?

Todd

mikedsilva · 07-21-2016, 11:05 PM

Quote:

Originally Posted by toddu

What causes pitting on a cam like that?

Todd

Apparently from very infrequent use and long periods of sitting. Some also say it can be the oil they have run.

toddu · 07-22-2016, 03:36 AM

Oh man, I'm going to go drive my car now!

Todd

gtc · gtc's Garage

Quote:

Originally Posted by toddu

What causes pitting on a cam like that?

Todd

It's called adhesive wear. Inadequate lubrication allows the cam and follower surfaces to touch and cold weld together. Then bits of metal are pulled off of one surface.
Typical cause is running an oil with inadequate film strength (wrong weight or additive content)
Generally the pieces of metal are so small that you don't need to worry about fragments... they will get caught in your oil filter and on your sump plug magnet.

toddu · 07-22-2016, 11:32 AM

Well, I drive my car this morning before it got too hot anyway ;-). I'll use any excuse I can. It's also always full of Brad Penn.

Todd

mikedsilva · 07-22-2016, 11:36 AM

Nice work.. how how is it in the usa this time of year anyway?
GTC post above makes me think I should not bother splitting the case...

I had a good look through using an ebay borescope camera (not that great) but the inside of my case is very very clean with almost no residue at all......

Sboxin · Sboxin's Garage

Quote:

Originally Posted by mikedsilva

Nice work.. how how is it in the usa this time of year anyway?
GTC post above makes me think I should not bother splitting the case...

I had a good look through using an ebay borescope camera (not that great) but the inside of my case is very very clean with almost no residue at all......

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,

onevoice · 07-30-2016, 06:19 AM

Quote:

Originally Posted by jdbunda

I just went through trying to figure out which bearings to use for my rebuild. Forum wisdom seems to be that the Glyco mains are generally fine, but the Glyco rod bearings (neither are made in Europe any more) have been considered suspect, due to several instances of new bearings being found to be out of spec. The bearings sourced from Porsche - which are apparently also sourced from Glyco - may have been at least been subject to some quality control and measurement, and therefore might be better. Several threads on this topic if you search.

My experience here:

Glyco vs clevite rod bearings - with data

Everything that goes into a rebuild should ALWAYS be measured. Glyco has certainly made bearings that are fine, but the ones I got were complete garbage.

AVI_8 · 07-30-2016, 09:16 AM

Quote:

Originally Posted by jdbunda

I just went through trying to figure out which bearings to use for my rebuild. Forum wisdom seems to be that the Glyco mains are generally fine, but the Glyco rod bearings (neither are made in Europe any more) have been considered suspect, due to several instances of new bearings being found to be out of spec. The bearings sourced from Porsche - which are apparently also sourced from Glyco - may have been at least been subject to some quality control and measurement, and therefore might be better. Several threads on this topic if you search.

It's my understanding that there are 2 manufacturing facilities for glyco bearings, the ones from Porsche are made in Europe, the OEM ones are made, I think in South Africa if my memory serves me correctly, the ones from Porsche are much more costly than the oem ones but should be to spec, given the previously known issues with the eom ones I wouldn't go with them.

RedCoupe · 07-30-2016, 09:31 AM

Quote:

Originally Posted by toddu

What causes pitting on a cam like that?

Todd

This is typical camshaft wear when the hardened surface is breaking down. Once the hardened layer is completely gone, it gets nice and smooth and shiny again but unfortunately it wears very fast and you wind up with a flat cam lobe! I agree with GTC that lubrication is critical for long cam life, but this type of spalling or pitting is often seen on a well worn cam.