Flywheel bolts - 901 vs. 915

[lkadams]

There are 2 part no's listed for flywheel bolts (bolting flywheel to crank, not clutch to flywheel).
Early 901 flywheel - 999.067.007.02
Early 915 flywheel - 911.102.171.00

I am assuming the difference here is the length of engagement of the bolt, as they are both 6 bolt flywheels. What I want to confirm is that it is not a change in the crank.

I have a 69 2.0 with a later 72 915 trans (and flywheel) and I want to replace the flywheel bolts when I reassemble. I am assuming that for the later flywheel, I need the 911. part no. bolts. I just wanted to confirm if someone indeed knows the distinction between the two.

Thanks!

[Jon B]

Keith,

The flywheel bolt change occurred with the 2.2 engines.
If you use a pull clutch and flat flywheel on your 69 engine, you must use the later, shorter bolts and 3mm disc under the bolt heads. The original 69 bolt disc was 4mm thick.

Jon B.
Vista, CA

[lkadams]

Thanks Jon for that - noted on the 3mm disc - will be sure to capture that.

[Jon B]

From the 911 Workshop Manual, page SE 54...
"Make sure that machine washer has a thickness of 3 mm."



Jon B.
Vista, CA

[Elferhelfer]

Hallo together,
does anybody of you know, if we could use the ARP Bolts 204-2802 for the early 901 gearboxes. They look like a very good alternative for me...

[304065]

Elfer,

Today we use the ARP bolts, these are very high tensile strength and do not need to be replaced after every use like the old KAMAX bolts.

ARP part number is 204-2802, they are around $40USD per set. (vs. $14/each or $84/set for Porsche)

I used these with great success in my 901/05 (1966) 2,0 liter motor. The ARP are on the left, they are a little shorter than the KAMAX although those have probably elongated.



I use a stripe of Loctite 242 on the threads and torque to 95 ft/lb using a "Triple Square" XZN bit. Take a file and square off the end of the XZN bit so that it fits all the way into the internal wrenching feature (you do NOT want to strip a flywheel bolt!)

And Good Luck!

[72targa]

Interesting info. I will assume they are shorter in alignment with their explicit instructions to NOT USE WASHERS with their bolts?

[304065]

They mean flat washers, not the steel disc. If you don't use the disc then the flywheel won't be tight to the end of the crank. Use the disc as normal.

[Jon B]

The factory bolts were shorter as of 70 model engines, except for the 914/6, than bolts used on earlier 2.0 liter engines.
The new, shorter bolts were identified by having a groove around the head, and were meant to be used with the new, thinner 6-hole machine washer or disc.
You'll notice the ARP instructions indicate that their bolts are meant for 1970-77 applications.

John, they seem to be instructing us not to use the 6-hole machine washer with their bolts: [3] "Make sure there is an adequate chamfer around the bolt holes on the flywheel to clear the radius under the head of the bolt."
Also "Flywheel Bolt without Washer - Installation".
I'd be curious to know the underhead length of the ARP bolts. The machine washer provides a more accurate, hardened face than the flywheel surface does.

You can always use the later, shorter factory bolts, with the 3mm machine washer, on earlier 2.0 liter engines.

Jon B.
Vista, CA

[304065]

Jon,

I thought the same (omit the disc) and tried it like that but the flywheel flopped around like a Flammkuchen just out of the oven. The shorter bolts bottom in the holes before preload can be achieved. So I used the washer. Later on disassembly after my THIRD oil seal failed, I noted no ill effects like galling, marring, fretting etc. If I ever do the FOURTH oil seal over again (and may lightning strike my upraised Stahlwille torque wrench if I do) I'll check it again.

We talked about bolt length here four years ago http://www.early911sregistry.org/for...n-needed/page2

and just for the record I am STILL in awe of your factory tool collection.

Of course there is less engagement which is a limitation, but the preload is the same.