964 3.6l crankshaft mesurements

Porshaah · 04-03-2011, 05:14 AM

The shop manual quotes the dimensions for the main and big end journals as 59.971mm to 59.990 mm (i.e. 2.36106" to 2.36181") and 54.971mm to 54.990mm (i.e. 2.16421" to 2.16496") respectively. Are the smaller dimensions in these ranges the wear limit of a standard crank or is there an acceptable wear limit which goes beyond these smaller dimensions? Or is the only way to tell if crank requires machining is to measure the clearance using plastiguage? My main and rod journals measure on average 0.3 and 0.2 thou respectively, less than the smaller dimensions quoted.

lucittm · lucittm's Garage

My TDWG book shows the wear limit on main bearings 1-7 is 59.960mm (2.360") and main 8 is 30.970mm (1.219"). The rod journal wear limit is 54.960mm (2.163").

Your mains and your rod journals are out of spec by .002 and .001 , on average.

Mark

Flat6pac · 04-03-2011, 05:20 PM

For general info, the old German machinist use to tell me its either in spec or its not in spec and needs to be made spec.
I set my calipers at 59.97 and if the mains clear the caliper its under standard. I measure 3 sides of the same bearing.
If I question what I feel, its time to get the machinist involved because I know he has more precise measuring equipment.
Bruce

cgarr · cgarr's Garage

A warm crank can grow a thou....

tom1394racing · 04-03-2011, 06:10 PM

Here's what you should expect for a 3.6 Crankshaft

Porshaah · 04-04-2011, 07:52 AM

The actual measurements for the crankshaft:
Rod big end journals range from: 2.1640" - 2.1641" or 54.9656mm - 54.9681mm
Main journals range from: 2.3606" - 2.3608" or 59.9592mm - 59.9643mm

tom1394racing · 04-04-2011, 09:48 AM

I t looks like your measurements are above the wear limits so the crank should be reusable.

You should also check for run-out and cracks.

Porshaah · 04-04-2011, 01:50 PM

"I t looks like your measurements are above the wear limits so the crank should be reusable."

Just barely usable. I also have one big end journal that either needs to go down to 1st undersize or have it welded / ground / hardended back to standard. Maybe I'll see some growth after hardening? I'm beginning to suspect the bearing spun because the crank has worn to this point.

tom1394racing · 04-04-2011, 03:25 PM

It's usually the other way round...The journal wears because of a spun bearing caused by oil starvation.

It the journal surface does not give good repeatability for diameter and if the surface has imperfections that catch your fingernail...it needs to come down in size or be re-welded.

Porshaah · 04-04-2011, 04:33 PM

No signs of oil starvation or blueing on #3. Local machine shop tig welds and hardens with some process I have to find out more about, but I'm leaning towards trying to find a good used std/std crank, hopefully one which has more life than mine. An alternative is grinding to 2nd undersize as the 1st undersize bearings are around $600.00, whereas 2nd undersize are around $250.00.

porschers · 04-10-2011, 03:41 AM

Does any body have 996 GT3 crank specs.?

Porshaah · 04-26-2011, 05:22 AM

On further inspection I've discovered that the P/N stamped on the main bearings are 930.132.03 (i.e. I expected to see a 964-101-901-00-M41 or 964-101-901-51-M100 P/N) and according to this thread: < http://forums.pelicanparts.com/911-engine-rebuilding-forum/311760-main-bearing-question.html> it appears that they are intended for an 1983 SC engine. It would appear that there has been some "creative machining" performed on my engine by an PO or is this standard machining practice? Both the P/N's appear to be missing a few digits and if the 930.132.02 is a standard size, is the 930.132.03 an oversize?

Your responses are appreciated

NoEardGoat · 02:04 PM

Quote:

Originally Posted by Porshaah

On further inspection I've discovered that the P/N stamped on the main bearings are 930.132.03 (i.e. I expected to see a 964-101-901-00-M41 or 964-101-901-51-M100 P/N) and according to this thread: < http://forums.pelicanparts.com/911-engine-rebuilding-forum/311760-main-bearing-question.html> it appears that they are intended for an 1983 SC engine. It would appear that there has been some "creative machining" performed on my engine by an PO or is this standard machining practice? Both the P/N's appear to be missing a few digits and if the 930.132.02 is a standard size, is the 930.132.03 an oversize?

Your responses are appreciated

I just took apart my 1992 M64.02 motor and I have the exact same main bearings (930.132.03 4343 10-90). Could Porsche have used some left over parts from 930's in our motor, or have both been previously tinkered with?

My rods are numbered: 930.103.121.2R
(s) 075F 45

Please help us....

Porshaah · 08-21-2011, 03:31 PM

Quote:

Originally Posted by NoEardGoat

I just took apart my 1992 M64.02 motor and I have the exact same main bearings (930.132.03 4343 10-90). Could Porsche have used some left over parts from 930's in our motor, or have both been previously tinkered with?

My rods are numbered: 930.103.121.2R
(s) 075F 45

Please help us....

My rod bearing P/N's are 930.147.01. Because 911 crankshaft main and big end journals are the same for the 930 and 964 (i.e. as well as other years prior) Porsche was likely using up old stock.

I've been doing more measurements and they don't seem to be making any sense. Main bearing sadles measure 0.004" larger than the standard 65.000 - 65.019 mm (2.55906" - 2.55980") spec. But when I plastigage the main bearing (i.e. I plastigaged 2 times) they're 0.002" - which from what I understand is OK. I then tried to measure the old bearings while torqued in the case with a bore guage, as this is the prefered method at 12, 1, 3 and 4 O'clock planes, and I get measurements ranging from 0.0015" to 0.004". How does one measure bearings without scratching the bearing surface? I don't mind scratching the old bearings but I'm reluctant to to the same after the crank is machined and new bearings are fitted. Do I just fit the bearing my machinest specs without measuring?

Any help is appreciated

BoxxerSix · 08-21-2011, 07:00 PM

Have you checked you mics against a know good standard to ensure their accuracy, and taking your measurements at proper temps(~68F)?

matt demaria · 08-22-2011, 03:43 PM

On old cases I usually get ovality in the approximate 45 degree axis from the horizontal. Also about 3 to 4 thou over. I believe that the crank pounds the bearing into the case and deforms the case. (Maybe related to detonation?) If you put new bearings in the hole they initially will be round untill the crank pounds them to an oval configuration quicklyto match the case diameters. __No support between round bearing and ovalled hole. The more clearance that develops in this oval clearanced area allows much more oil to escape and not leave a film to support the crank bearings and also robbing oil supply to the rods..