ARP Studs/Bolts Questions

[jonnyb]

I'm rebuilding a motor that has ARP head studs and rod bolts in it. Up until now, I've only used MP head and rod bolts.

Do I torque them to the same specs as factory, or is there an ARP spec I should use?

[turbovanman²]

http://www.turbo-mopar.com/forums/showthread.php?t=6416&highlight=main

[jonnyb]

Ah - the good old KC. I should have checked there before posting.

Thanks Simon.

EDIT: Actually, I do still have a question. Do I torque them in stepped increments up to 80-85 (e.g. first go round 45, then 65, then 85), or do I just torque them in the factory pattern right up to 80-85 on the first go round?

Thanks again.

[crazymadbastard]

I would step them.

[GLHNSLHT2]

I step them. 45-65-85-85. Get a heat cycle in them and retorqe.

[mock_glh]

Whoa, guys! Head studs have a finer thread pitch than stock bolts. They should be torqued to 70 ft lbs, NOT the 85/90 ft lbs like the bolts get. Rod bolts are the same pitch as stock ones and get torqued the same as stock ones (50 ft lbs).

[GLHNSLHT2]

If the thread pitch is finer than stock bolts than 70ft lbs wouldn't squish the gasket as much as 85, right? What's the reasoning to use less torque on the finer threads? Just less material on the thread to hold the pressure?

[Pat]

Finer pitched threads create more leverage for the downward force on the head. It's like steeper gearing.

If one nut turn = say 1/8" of vertical movement, it will take certain amount of turning torque on the nut to create a certain amount of downward push on the head. If one nut turn = 1/16th of an inch of vertical movement, it will take less turning torque to produce the same amount of downward force.

Crappy explanation, but that's how I reason it in my little pea brain.

[mock_glh]

If the thread pitch is finer than stock bolts than 70ft lbs wouldn't squish the gasket as much as 85, right? What's the reasoning to use less torque on the finer threads? Just less material on the thread to hold the pressure?

The smaller angle of a finer thread requires less torque to make the same clamping pressure. You do have to turn the fastener more to get the same amount of stretch.