crank pulley bolt - washer or no washer

[smestas]

Wayne,

I have a pulley made for AC but my question is do I or dont I use a lockwasher under the pulley bolt. All the diagrams I have show a lockwasher under the bolt but in the apendix A of your book it only refers to the lockwasher only for the non-AC pulley. Could this be the reason for the two different torque settings?

I aso wanted to know if there are two different part numbers for a crank pulley bolt? I ordered one (K-093-005-02) from you guys but noticed that in apendix A the AC pulley bolt has a extra measurement listed from the non-AC bolt. Did I get the right one?

[Wayne at Pelican Parts]

There have been a gazillion versions of the front pulley. It's probably best to use a lock washer if the factory originally called for it. I would compare the bolt that comes to the one that was in there before. I know, not a scentific and definitive answer, but it's probably the easiest thing to do...

-Wayne

[Damomma]

My 78 with AC pulley had no lock washer. It hadn't been off since 1987.

[Jim Sims]

Some background from an almost disaster with a '73 T air conditioning pulley installation; during which a concern developed when a manual (Porsche specifications book) appeared to be recommending tightening an M12 class 8.8 screw to 110 ft-lbs which would almost surely fail the screw.

In most of the early 911's prior to 1978 the crankshaft pulley screw was a M12x 1.5 x 22 mm long hex head plated cap screw of strength class 8.8 (PN 900.083.001.02) and it was used with a 12mm spring or wave washer (PN 900.028.014.01). This screw could only be tightened to 80 Nm or 59 ft-lbs due to it's strength class. This combination was used for both A/C and non-A/C equipped engines. A spring or wave washer is almost worthless as a fastener locking appliance so it is interesting to note that in the mid-year Turbo's and Carreras with A/C that the pulley screw changed to PN 999.093.005.02 (also M12x 1.5 x 22). This screw is of the "Durlok" form (http://www.franciskirk.com/screws.html) and is of strength class 12.9; this screw is tightened to 170 Nm or 125 ft-lbs (which is higher than a normal plated class 12.9 screw tightening torques of 140 Nm or 103 ft-lbs) due to the Durlok locking features consuming some of the tightening torque. A spring washer was not shown being used with this screw. Beginning in 1978 the spring washers were not being used on any of the pulleys but the pulley screw for all cars (through 1989) was the 999.093.005.02 part number.

If you received a Porsche part number screw 999.093.005.02 you have the correct part. The head likely has the number 12.9 embossed on it and under the head there may be serrations. A wave washer is not used with this type of screw. The extra number (22) in Wayne's book is the screw's length in mm. All of the pulley screws were 22 mm long (length is measured from the bottom of the head to the tip of the thread). Tighten to 125 ft-lbs (no lubricant on the threads). Cheers, Jim

[smestas]

Originally posted by Jim Sims
The head likely has the number 12.9 embossed on it and under the head there may be serrations. A wave washer is not used with this type of screw.

Jim,

Thanks for the explanation and good info! I checked my bolt and I did receive a bolt with a 12.9 stamp and serrations on the bottom. Woooo Hooo! I can sleep tight now.

Now if I can only find a used non-a/c pulley......

PS - Anyone need a FREE pulley bolt washer?

[Wayne at Pelican Parts]

Great info Jim!

-Wayne

[KTL]

Just as an aside, those Durlok screws can be a bear to get off as well. The serrated head bites into the pulley just right and can make for some serious torque needed to get that bugger loose. If one is removing the Durlok with the motor in the car, an impact wrench is the way to go if you don't have much room to get your breaker bar in there.

Thumbs up to Jim. Always provides excellent fastener info.

[Gregsgroup]

The value of this forum contains to amaze me. Even a post from 5 years ago is still relevant. Makes we want to continue to support our host. Thanks Wayne.