Head Re-torque After Initial Run

I need to check the torque on my cylinder head now that I've finished my rebuild and had the engine up to operating temperature. Here's a question that I've never really known the answer to:

When the torque is checked, is it best to back off the nut a little and then torque to spec? Or is it best just to torque to spec and if it doesn't move it doesn't move?

I have heard that you should always back off the nut because the initial torque you will be reading is the break-away torque. This is how much torque it takes to get the nut started turning and is usually more than running torque. So, it's possible that you could run the torque wrench up to spec and not move the nut, but if you had kept going it may have broken loose and then read under spec. Make sense?

Anyway, how do you guys do it? Just check it or slightly loosen and then retorque?

On mine, the torque dropped about 30% below spec after the initial run-in... so I didn't need to back it off to retorque it (I just had to torque it back up to spec).

I know what you mean: there are two coefficients of friction: static and moving, and the former is always higher than the latter. It takes a little more torque to get it moving, then it drops a bit and comes back up as you torque it. I don't know if that small difference is enough to worry about.

This is really only necessary if you are using stock studs.

Jay

APE Jay wrote:

This is really only necessary if you are using stock studs.

Jay

Jay - I'm running APE studs and nuts. What do you recommend? A little higher torque than stock? Do I need to back them off just a little first?

Also, on a side note, I have a tiny leak at the base gasket. Any chance this is going to seal up??

79MKII wrote:

Also, on a side note, I have a tiny leak at the base gasket. Any chance this is going to seal up??

I doubt it.

You didn't say if you replaced it during the rebuild? When I rebuilt mine, the new Athena base gasket disintegrated within 200 miles and I had to tear it all the way down to the rods and do it again. Hope your gasket isn't a POS like mine was.

We recommend 36 to 42 lbs

Jay

APE Jay wrote:

We recommend 36 to 42 lbs

Jay

That sounds about right, my factory manual specs mine at about 30 - 32 as I recall.

You get better accuracy if you use a torque wrench with a max range of about 0 - 600 in-lbs (which is 0 - 50 ft-lbs)