Pagoda SL Group

W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: drooman on November 27, 2021, 20:32:41

Title: Crank bolt torque / methods
Post by: drooman on November 27, 2021, 20:32:41
I searched the site and the tech manual, found two conflicting pieces of data on the crank bolt torque.

Engine: 1969 280SL  with  Automatic trans

I replaced the crank seal (was hard as a rock might have been original)  I made the appropriate tools
to install the seal properly without folding it. There was a lot of info on here about that, and it was very helpful.

Ready to reassemble, what is the torque spec of the crank bolt? ( I read 150 AND 200 ft/lbs on here) this is a  significant difference.

Also, any particular stacking that is correct for the spring washers?  Some  Porsche designs using these types of washers call for “ front to back “ stacking.  Mine were stacked like you would stack dinner plates in a cabinet..with the high centers facing the bolt head.  “ front to back” washer stacks would be like if you stacked every other dinner plate upside down.  Which way do these go? I don’t trust how I they came out considering other former repair  “efforts” I have found on this car.

Finally, any tricks for Holding the crank for the torquing installation? I can make a holding tool but before I do I’d like to hear what others have done.

Thanks everyone!
Title: Re: Crank bolt torque / methods
Post by: ja17 on November 28, 2021, 07:58:06
The crankshaft bolt with threaded straight sides gets torqued 21+1 mkp or 151.62 ft/lbs. + 7.22 ft/lbs. (Factory Shop Manual Late BBB p. 00-0/2 and 03-1/20). Some engine use three heavy flat washers.  The cupped washers are actually "Belleville springs" .  The BBB refers to them as "plate springs". They must all be installed with the convex side outward against the bolt head. An upgrade modification was offered in which a crankshaft stretch bolt (partially threaded with tapered sides) was used with the three of these plate springs. With the stretch type bolt the torque is 160 ft/lbs. then 90 to 100 degrees of additional rotation. The Early BBB has diagrams and information on the stretch bolt versions page 03-10/2. As far as bracing the engine, the Factory BBB simply states "counter hold at flywheel" while applying the torque. Most likely a special factory tool is involved. Normally I can find a safe way to position a heavy pry bar so as to lock the engine from turning while removing or installing the bolt.