M96 3.4L Crankshaft Journal Measurements
#1
Racer
Thread Starter
M96 3.4L Crankshaft Journal Measurements
Tonight I measured the crankshaft main & rod journals from my M96 3.4L. It was removed from a re-manufactured engine (by Porsche) with approximately 37,000 miles. What measurements do you guys have? In a few days, I'll be shipping the crank out for magnaflux, balancing, and journal polishing. Photos below.
See updated measurements in post #16 below: https://rennlist.com/forums/996-foru...l#post15250757
7 Main Journals, Inches
Direction: Crank Pully (A) --> Flywheel (G)
A: 2.360
B: 2.360
C: 2.360
D: 2.360
E: 2.360
F: 2.359
G: 2.360
Rod Journals, Inches
1: 2.086
2: 2.084
3: 2.084
4: 2.086
5: 2.086
6: 2.085
See updated measurements in post #16 below: https://rennlist.com/forums/996-foru...l#post15250757
Direction: Crank Pully (A) --> Flywheel (G)
A: 2.360
B: 2.360
C: 2.360
D: 2.360
E: 2.360
F: 2.359
G: 2.360
Rod Journals, Inches
1: 2.086
2: 2.084
3: 2.084
4: 2.086
5: 2.086
6: 2.085
Last edited by Doug996InKC; 08-29-2018 at 12:24 AM.
#4
Burning Brakes
So you just measured the diameters? I would think the runout would be more useful, will tell you how out of round they are if at all.
Another measuring tool you should consider when putting this back together is plastigauge, it will give you a measurement of the shell to crank surface clearance on each.
Another measuring tool you should consider when putting this back together is plastigauge, it will give you a measurement of the shell to crank surface clearance on each.
#6
RL Community Team
Rennlist Member
Rennlist Member
Yeah the bearings have heat marks.
Are they evenly worn?
Are they evenly worn?
#7
Burning Brakes
I have measurements for a 3.6 (not on me right now though) so don’t know how helpful my data is to you. Considering how your measurements are so consistent, you are probably good. IIRC, clearance should be around 0.0015. Torqued bearing carrier and rod caps with bearings and measured diameters might be worth doing to check.
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#8
Rennlist Member
Looking at your measurements you have a problem. .002 variation on rod journals is WAY too much. There are no "select fit" bearings available So there is no way to correct the variation. Even the coated bearings are only coated to .0005.Suggest you remeasure with a micrometer with accuracy of ten thousands, or have someone else measure.
#9
Burning Brakes
Sorry, only saw the crank journals measurements and I agree, you need an additional decimal place.
If you need journals welded/repaired, I’d talk to Nick at Shaftech.
If you need journals welded/repaired, I’d talk to Nick at Shaftech.
#10
Rennlist Member
Ahsai might have them, send him a message.
#11
Racer
Thread Starter
I haven't measured the bearings yet. I need to invest in more precise micrometer.
Looking at your measurements you have a problem. .002 variation on rod journals is WAY too much. There are no "select fit" bearings available So there is no way to correct the variation. Even the coated bearings are only coated to .0005.Suggest you remeasure with a micrometer with accuracy of ten thousands, or have someone else measure.
I hope I can chalk up these variations to a cheap micrometer, and my inexperience. Thanks for the lead!
He has measurements for the 3.6, not the 3.4.
I appreciate all of the input, guys. I'm leaning towards purchasing a Fowler micrometer and re-measuring. This is more for peace of mind, before shipping the crank to the shop that will magnaflux, rotate, and balance.
#12
Burning Brakes
Check your rod bushings. They might still be in spec relative to the broad, older model specs, but the engine quench is very tight so I would recommend replacing them.
#13
Racer
Thread Starter
#14
Rennlist Member
New factory OEM main bearing carrier bolts and rod bolts can only be torqued 4 times. Suggest you use the old bolts for torqueing and testing/measuring. Arp2000 bolts (should be included with Corillo Rods) can be torqued many times. No problem from torqueing the bearings many times. Since you are balancing the rotating assembly, you will be sending the rods and bearings with the crank, so have the machinist assemble the rods and bearings , torque and measure, and measure the crank journals and provide/record bearing clearance. It's more accurate than plastigauge, but plastigauge done correctly is acceptable.