Back off 1/4 or no on head retorque

[doctorgonzo]

Saw conflicting theories in a search. I'm going to retorque my head today (200 miles on rebuilt engine) as part of changing oil and adjusting valves. Finishing up the G post rebuild so I can get it out of the work bay to pull in the 1100E for teardown. Back off 1/4 turn then torque, or just make sure torque is correct?

[Nessism]

I suggest trying to move the nut forward first and if it won't move, trying backing it off just enough to get it moving and then tighten it.

Just retorqued the head on my recently rebuilt 1000 engine and the nuts were surprisingly loose.

[Agemax]

you pnly need to re torque. do not back the nuts off first! if you do it breaks the origonal seal created by the first torquing down.
set the wrench to the correct torque and go through each nut in the correct sequence. if they dont move, dont worry it means they are all fine

[doctorgonzo]

Hoping one or more is a little loose. Very slight weep at the head/cylinder junction on the left side. Very slight weep, but it's there.

[Nessism]

On a newly rebuilt engine the nuts shouldn't be seized on studs so you can usually go straight to tightening. On an older engine though, where there is likely to be corrosion in the threads, cracking the nuts loose a smig won't release enough clamping load to matter but it will allow you to get a proper gauge on the clamp load.

[Agemax]

On a newly rebuilt engine the nuts shouldn't be seized on studs so you can usually go straight to tightening. On an older engine though, where there is likely to be corrosion in the threads, cracking the nuts loose a smig won't release enough clamping load to matter but it will allow you to get a proper gauge on the clamp load.

if there is corrosion on the threads then that will give you a false torque reading anyway.

[Nessism]

if there is corrosion on the threads then that will give you a false torque reading anyway.

Stiction in the threads typically causes a false torque reading, particularly on threaded fasteners that haven't moved in a while. Once you overcome this initial resistance for the fastener to move, the nut will tighten smoothly even if there was some corrosion creating a high amount of stiction.

[Steve]

Shoot, I thought he was wondering about my favorite torque values, ...

"Tighten it until it strips, then back off 1/4 (or 1/2) a turn."

.

[Agemax]

Stiction in the threads typically causes a false torque reading, particularly on threaded fasteners that haven't moved in a while. Once you overcome this initial resistance for the fastener to move, the nut will tighten smoothly even if there was some corrosion creating a high amount of stiction.

you will only get an accurate torque reading with an accurate wrench on fasteners that are spotlessly clean and dry

[doctorgonzo]

you will only get an accurate torque reading with an accurate wrench on fasteners that are spotlessly clean and dry

Against my usual pattern I didn't replace the cylinder head studs, but they were well cleaned on install, and the nuts are all new.

[Agemax]

Against my usual pattern I didn't replace the cylinder head studs, but they were well cleaned on install, and the nuts are all new.

a straight re torque will do the job then

[doctorgonzo]

Whoa, you weren't kidding Ed. 200 miles from the original bolt down, and 6 of them were WAY loose. several turned a 1/4 turn or more. 2 turned a good 3/4 to a full turn. Amazing.

[Agemax]

Whoa, you weren't kidding Ed. 200 miles from the original bolt down, and 6 of them were WAY loose. several turned a 1/4 turn or more. 2 turned a good 3/4 to a full turn. Amazing.

sounds to me like they werent torqued down properly in the first place. or your torque wrench is wildly innacurate.
3/4 of a turn is no way just a run in check, thats a loose nut!

[Nessism]

Whoa, you weren't kidding Ed. 200 miles from the original bolt down, and 6 of them were WAY loose. several turned a 1/4 turn or more. 2 turned a good 3/4 to a full turn. Amazing.

Athena MLS head gaskets loosen up quite a bit. Hopefully you caught it in time.

[Agemax]

Athena MLS head gaskets loosen up quite a bit. Hopefully you caught it in time.

seriously bad quality gaskets then if they loosen up by one full turn, thats over 1 mm of clamping force on the gasket
i retorqued the cometic gasket on my engine after 500 miles and the wrench clicked on every nut without moving it