Speedtoys

Shouldnt slip. Theres a lot of coverage on the pulley with how the tensioner is located.

Unless you're Sean, and you got oil on the belt.

But if it was a problem..and it hasnt been, Id do this:

http://www.carbiniteracing.com/index.html

Speedtoys

Edited..did the conversion, but didnt type it in as Nm.

Problem with store & rent, is thats 20mi away. Bout 5hrs of bus rides/waiting.

(need to buy one of these...)

Imo000

I lost my crank bolt during the SC shake down testing. Had a little damadge to the crank, like you. Fixed it, like you and then, pulled the radiator, locked the flywheel and used an inpact gun and blue loctite to get the replacement bolt in. Has been on there for a long time.

Jim Devine

If you can't get a name brand wrench, this is better than nothing:
http://www.harborfreight.com/3-4-qua...rench-808.html

Speedtoys

And...back together, and survived 3mi to dinner.

Will drive N/A for a few days, and go back to being a boostard this weekend.

Z

In at least some cases, the longer bolts were used because the portion of the crank pulleys used with some supercharger systems was made thicker than on a stock crank pulley.

Actually, at least part of the reason it came loose is because it's the stock crank pulley. The stock crank pulley configuration is fine for running the stock accessories, but it was never intended to run the stock accessories and a supercharger. There is a significant difference between those two.

As Dan mentioned, there have been cases of the crank bolt coming loose on supercharged cars, even when the crank bolt had been properly installed. Some owners caught it when the bolt and pulley were just loose, but some had them come completely off while driving. This occurred with supercharger crank pulleys from a few different sources, and was due at least in part to poorly thought out and designed crank pulleys for the application. A well thought out crank pulley configuration isn't going to have this issue, unless the crank bolt is installed with a torque significantly lower than the stock specified value.

I know there was at least one supercharged 928 owner that had his crank pulley come loose multiple times before switching to a different one. The new pulley he installed had been designed to address the issue causing the problem, and it never happened again. The crank pulley is one of the items that Murf928 has sold to some owners of supercharger kits from other suppliers, to resolve problems that they were having with those other kits.

Using a new, longer, stronger, crank bolt, tightening it to a higher than stock specified torque, and applying Loctite may help keep the pulley tight longer, but it still may not keep issues from developing eventually if the crank pulley configuration being used isn't designed to handle the job it's being asked to do.

mark kibort

yes^^^^^^^^^

the supercharger is trying to losen the belt, with a substantial amount of force. by the way, you dont need a torque wrench. yes, just jump on the 1 ft long wrench (your 1/2" drive) 220 to 240 would be fine to try and counteract the forces of the supercharger, which can have some peak torques that might still losen the bolt, so i would check it from time to time. (although kind of a hassle , unless you use the brakes to lock the rear wheels in gear if you dont want to use the flywheel lock tool)

How much power are you making with the set up now??

Mongo

This happened to me on my 944 track car a while back. Use a little loctite blue midway on the threads (use only enough for 2-3 threads - for supercharged cars, just double the amount of threads as stated before that are saturated with loctite) for the crank pulley bolt. It should never back out again. When you tighten it, do the factory torque spec (or as tight as you can get it BY YOURSELF). You will still be able to break the bolt loose once you decide to get back in and do your timing belt.

Z

Technically, the supercharger and accessories are trying to keep the crank pulley from turning. The pulley is held against the head of the crank bolt, so it's trying to keep the bolt from turning. This is occurring while the crank is turning clockwise, so the effect is like the crank trying to turn itself off of the bolt. If it were a left hand thread, it would be trying to tighten against the bolt.

The force produced by the turning crank is not smooth and constant, like when you're pulling on a torque wrench to tighten the bolt. The engine is a four stroke V8, so it fires four times every rotation, producing four power pulses every rotation as a result. It's more like an impact gun repeatedly applying force, instead of a smooth constant force acting on the crank pulley, and therefore the crank bolt.

Using something like Loctite may lock the bolt into the crank, keep it from turning in relation to the crank, and working it's way out. That's not necessarily going to keep the crank pulley from turning in relation to the crank and bolt though. If that occurs, over time there will be wear, and the pulley will be loose, even though the crank bolt hasn't moved in relation to the crank. Friction is the only thing trying to keep the stock crank pulley, as well as the crank pulleys supplied with some supercharger kits, from doing that.

Tampa 928s

Do i need to worry about this and get a redesigned pulley for my Murf kit?
If so where can I get one?

Z

No, it's not an issue with any of the Murf928 supercharger kits. The crank pulleys that have always come with the Murf928 kits are designed so that this does not happen with them. Even if someone were to pretty significantly under torque the crank bolt, I'd have a hard time imagining the issue occurring with one of the Murf928 crank pulleys.

Dave928S

You can add an extender to a torque wrench to double it's length from centre of drive to leverage point ... then 109ft/lbs on the torque wrench will give you 218 at your new extended drive point centre.

mark kibort

hmmm.. I have to think about that one.

James Bailey

Understand, since it is torque not horsepower.....

namasgt

Jeff,

How many miles since the last time you had that bolt loose and how many miles since the Rotrex install?