1971 Porsche 911 flywheel information needed

[VaporiZe]

I am restoring a 1971 Porsche 911e with my dad, when we took the flywheel off we had to put a 5ft bar on the wrench and put our full weight on it to get the bolts off. I dont think it should have been that hard to get the bolts off and was wondering if anyone knows the torque specifications for the bolts so we can put it back on correctly.

[mike curnow]

the spec book for a 1974 says 15 mkp

[Jon B]

the spec book for a 1974 says 15 mkp

Correct for 1971 as well.
15 mkp = 108 lbs-ft

Jon B.
Vista, CA

[304065]

Throw the bolts you removed in the garbage-- they are single use, "torque-to-yield' which means they permanently elongate when you torque them down. Look around the threads, do you see some pink chips? Those are the remains of red loctite which is frequently used on flywheel bolts as a precaution. Probably what happened is either 1) somebody put the bolts on with an impact wrench or 2) loctite was used or 3) both.

With regard to the 12 point (XZN) tool you used to take the bolts off-- carefully file the end of the tool down to remove any rounding-over of the end. When you have a big torque episode like that the end often gets buggered. By filing it absolutely flat you can assure that you have excellent contact in the internal wrenching feature of the new bolts, so they don't strip at the high torque setting. When I do this (I have been doing it a lot lately) I actually take a hammer and tap the tool into the internal wrenching feature (gently) to make sure it is seated.

I recommend the ARP flywheel bolts as these are high strength and are suitable for re-use. Follow their instructions to the letter. ARP 204-2802. They are also like $40 a set vs. $13 EACH for the factory Kamax bolts.

http://arp-bolts.com/images/releases/pdfs/204-2802.pdf

Good luck!

[VaporiZe]

Thank you for telling me this, however I looked at the threads and didn't see any pink on the the bolts or on the flywheel it self

[Mr9146]

Sometimes things just get happy with one another and don't want to let go; it's not always an indication of stupidity or foul play from a previous repair. But, as stated above, replacing the bolts is important.

[Jon B]

...we had to put a 5ft bar on the wrench and put our full weight on it to get the bolts off. I dont think it should have been that hard to get the bolts off...

My elves always use a 5 foot bar to remove flywheel bolts...

Yes, of course, replace those bolts as suggested. I didn't think you might consider re-using them.

Jon B.

[Fishcop]

Good to know there is an ARP alternative...

I must have spent $600 or more over the years replacing these bolts. I wonder why they stuck with the 12 point design? Seems a perfect opportunity to change to a large hex head arrangement? I've always hated cranking hard on those fasteners!

[gled49]

I don't know about all of you, but I have seen a lot of metal transfer from flywheel to the crankshaft. Very common in high revving race engines. It is hard to say if flywheels were really loose. Somewhere down the line the bolt grading on factory bolts changed from 140 marking to branding letters. The aftermarket bolts grading went to 12.9. We use to torque the 140 graded bolts to 150 lbs on race engines and never had any issues. The 12.9 grade bolts heads would pop off at 120 lbs. I worry that the ARP bolts at 90lbs just aren't tight enough? Gordon

[Flieger]

The 70.4 mm stroke cranks were less rigid so the torsional vibrations got shifted down to 8,000 rpm. 66 mm cranks were more rigid so it was higher than what the valve springs and rods could take. The 9 bolt cranks got around the issue with the larger bolt circle diameter giving the clamping pressure more leverage.