Flywheel Bolt Tension

Read through all the post and decided to order some ARP Flywheel bolts.

then Jeep Manual says to torque to 50 to 65 pounds. The instructions that came with the bolts say 75 pounds.

which should I follow?

 

The manufacturer's specifications.

 

When using ARP fasteners, always follow ARP's recommendation, as they aren't made from the same material, or have the same exact physical properties as the OEM ones. The steel is literally a different alloy. And I don't know about the flywheel bolts, but most ARP internal engine fasteners, like Head Bolts/Studs, Rod cap Bolts/Studs, and Main Bearing Cap Bolts/Studs, include their lube, and their published torque values are because you lube the threads.

 

One of the reasons a bolt “holds” is because at its recommended torque spec, it stretches a tiny bit and acts as a spring with preload. Not enough torque, and it doesn’t stretch. Too much torque, and it goes past its happy place and fatigues or all-out fails. If you’d only apply the stock torque to the ARP bolts, they wouldn’t have enough preload.

 

This is correct, the proper torque generally depends on the bolt not the application. Ideally they are torqued to a stretch value but that's difficult to measure so a torque value is substituted. Lubricating the bolts before torquing gives more consistent results and ARP has their own lube used to create their own torque charts.

ARP has a good explainer of proper bolt pre-load here: The Official ARP Web Site | Technical Information

This is their torque chart (using their lube): https://arpinstructions.com/generaltorque.html

 

Great advice! I’ll use ARP specs on both the fly wheel and clutch. Makes sense, thank you so much!

 

Honestly? I don't know what it is, exactly, but the closest thing I can compare it to, is a really light semi-fluid molybdenum grease. Or maybe oil impregnated graphite?

 

Agreed it's like a thin oily grease.

 

Most ARP bolts are 8720. Pretty tough stuff.

 

Over-torque is better than under-torque.

Caroll Smith says so. Motorbooks Workshop Ser.: Carroll Smith's Nuts, Bolts, Fasteners and Plumbing... 9780879384067 | eBay

 

Those are such great books. I have all of them.