safety wire flywheel bolts - good or bad idea?

[Bob Kontak]

Originally Posted by Ronnie's.930

Not if you use an air-impact . . . no heat required and easier than yer sister, Bro!!! Stick around and I'll learn you a thing or two yet!

My sister uses a saws-all sometimes with special silicone rubber "blades" (That's what she calls them). I digress.

Glad Packy is springing for new bolts. The more I think about it the more I am certain I did spring for new bolts in 99 when I had the trans re-done. May or may not have made a difference but given the coin I unloaded on the rebuild, flywheel re-face and Sachs Power Clutch package, I can't see myself saving a few bucks and re-using the old ones.

The 101 projects book mentions nothing with respect to lubricant or anti-sieze. Neither does the Hayne's manual. I have the factory manual and Bruce Andersons book at home. So I can check.

I am now confused, given absence of information, is clean and dry the norm for a street car? I would assume it is and I am pretty sure that is what I did. I have installed head bolts on cars where the instructions say clean with a touch of motor oil.

All of the variants (oil, Blue Loctite, Moly) can tweak the torque settings a bit as tharbert says.

However, on a street car, I bet dollars to doughnuts that if you torque them and the real value is between 60-70 ft pounds, given you torque them in the proper pattern, no risk.

FWIW: I just dropped $1.29 on a single doughut the other day at the local mega marketer gas station. Renders "Dollars to doughnuts" expression obsolete.

[Ronnie's.930]

Originally Posted by Bob Kontak

FWIW: I just dropped $1.29 on a single doughut the other day at the local mega marketer gas station.

One donut say you?! I call BS on that as I've never known you to eat less than twelve at a sitting!

PS - it's amazing what ol' Sis Kontak can do with a sawsall, for sure!

[KTL]

Factory spec is dry. Taken from '84-'88 technical spec book which mentions other fasteners like the head stud nuts and camshaft bolt using Optimoly HT (anti-seize paste)

[Bob Kontak]

Originally Posted by KTL

Factory spec is dry.

Outstanding. Just took a pic of my 3.0 spec book with my cell phone. Can't send it. Weather?

Says about the same thing. I will resend pic to my e-mail on the way home and post.

If not. Tomorrow with a regular camera.

[Packy]

When I was putting it all together I took my time going bolt to bolt opposite of each other creeping up past the torque spec. I got it out of Wayne's engine rebuilding book which I think states 66.3 ft-lbs. I used a little blue locktite, just a dab, and no moly. I was feeling uncomfortable with the moly.


Thanks for the help guys.

[Tom F2]

Factory manual, page E101, says to oil the threads of the bolts lightly and tighten them to 150 Nm. I think that all of the Porsche torque specs are for lightly oiled threads, unless otherwise specified. This is for an early, six-bolt flywheel.

[chris_seven]

Originally Posted by Tom F2

Factory manual, page E101, says to oil the threads of the bolts lightly and tighten them to 150 Nm. I think that all of the Porsche torque specs are for lightly oiled threads, unless otherwise specified. This is for an early, six-bolt flywheel.

The 6 bolt flywheel does, however, use an M12 Bolt, hence the higher torque.

Discussions about Torque to Yield fasteners (TTY) and Porsche engines continues to surface and in general this category of bolts doesn't seem to be very well understood.

In recent Engine Builder magazine review of TTY fasteners by Mahle-Clevite there are several inaccurate statements which don't help.

Basically TTY fasteners are tightened beyond their yield point and therefore deform permanently.

There are two reasons for using fasteners in this manner.

The first is when the clamping force needed for safe operation is greater than can be produced by an 'elastic' bolt. This used to be the case for the con rod bolts in early 2.0 litre engines but this changed when the rod was re-designed on the 2.2 litre engine.

Mahle-Clevite suggest that when a bolt is stretched beyond its yield point it loses some of its elasticity - this just isn't true. Even the most basic examination of a material's tensile stress/strain curve will show that this statement is incorrect.

The second reason is when nut runners are used and several fasteners are tightened at the same time.

By reducing the initial torque and then tightening to an angle the preload in likely to be more uniform with less scatter which is a good think.

I don't believe that Porsche flywheel bolts are TTY bolts and can be safely re-used unless they show signs of damage.

If you always use new bolts then the scatter of preload will increase due to variation in thread surface finish.

With regard to balance - I am not use small variations in the weight of lock wire will influence balance at the centre of the flywheel.

The bolts, for example are not match weighed and will vary.

I used to manufacture very high speed diaphragm couplings (100 000rpm +) and we used to critically match weigh bolts.

[DRACO A5OG]

Thanks Brother Kevin!

You saved me a bit of dough

Originally Posted by KTL

wayner's issue is why the larger cranks (70.4mm stroke & larger) eventually were revised to add 3 more bolts for a total of 9?

I thought the fear of the flywheel bolts started with the 6 bolt 70.4mm cranks that would loosen up their bolts due to harmonics and that gets ugly real fast. So guys started using high strength/red threadlocker and even over-tightening them. They can over-tighten them because the recommended torque spec. was much lower than the bolt was capable of (12.9 class bolt) and the forged crank material can handled the additional stress on the receiving threads, I assume?

Here's the instructions for the 9 bolt ARP bolts right from ARP. But don't use these instructions for regular OEM Porsche Verbus/Inbus bolts (also very high quality), which are plenty sufficient for a stock engine even when used hard. All the cars in our "fleet" of locals who've tracked them a lot for over 10 years have never had an issue with original flywheel bolts

http://arpinstructions.com/instructions/204-2801.pdf






I wouldn't safety wire them mostly because they're spaced so closely together and you'd have a real hard time routing your wire. Not to mention drilling 12.9 class bolts takes some patience. That's some hard metal you're drilling. Better have a high quality drill bit too........