Re-Torquing Head Gasket Bolts Correctly?

[Dibbons]

Back in the 1970's I remember re-torquing the steel shim head gaskets on a 273 build after the first cool down period after breaking in the camshaft. I did not loosen the bolts, only re-torqued them as they were.

I read online today that when re-torquing, the bolt should first be backed off a bit.

Not sure what is best. Probably boils down to who you talk to.

 

[HawkRod]

I read online today that when re-torquing, the bolt should first be backed off a bit.

The reason for this is because it takes a bit of force to begin to move a bolt, so if the bolt is very near (but not quite at) it's final torque value the torque wrench will click and you will think you have the proper torque. If the bolt is not near its final torque then it doesn't matter.

By the way, when putting any fastener together any place where metal touches metal should be lubricated. This means the threads, but also the underside of the fastener (and washer, if present). This will give you a proper torque reading. A dry bolt will NOT give you the proper torque reading.

 

[Runcharger]

Retorque Truck wheels all the time, never once have I heard of someone backing them off.

 

[beebest]

Be careful, huge difference between dry and wet torque values.

Bolt Torque Chart - Portland Bolt

Torque values for various grades and diameters of fasteners.

www.portlandbolt.com

 

[493 Mike]

The factory never retorqued head gaskets. How could they?
Mike

 

[dvw]

I was tought this by Dave Koffel years ago. Bring the fastener up to a minmal torque value (25-30lb/ft) to make sure everything is seated. Then following the pattern pull each fastener to full torque. When this has been completed start following the pattern a second time. Crack each fastener loose then pull it to full torque. I garauntee the fastener will rotate further the second time. Been using this method for 40 years. All types of stuff, 15-1 compression, boosted stuff. Never had a gasket fail since. Torque is a measurment of friction. If you don't loosen the fastener (unless it's already loose) the breakaway torque value will exceed the spec before the fastener rotates. Also using this method eliminates the need for hot retorque.
Doug

 

[Kern Dog]

I have never RE-torqued any engine fastener except header bolts since some gaskets do seem to compress a bit after a few heat cycles.

 

[chescharger]

Isn't torque a measure of bolt tension?

 

[WileE]

I was tought this by Dave Koffel years ago. Bring the fastener up to a minmal torque value (25-30lb/ft) to make sure everything is seated. Then following the pattern pull each fastener to full torque. When this has been completed start following the pattern a second time. Crack each fastener loose then pull it to full torque. I garauntee the fastener will rotate further the second time. Been using this method for 40 years. All types of stuff, 15-1 compression, boosted stuff. Never had a gasket fail since. Torque is a measurment of friction. If you don't loosen the fastener (unless it's already loose) the breakaway torque value will exceed the spec before the fastener rotates. Also using this method eliminates the need for hot retorque.
Doug

I have never RE-torqued any engine fastener except header bolts since some gaskets do seem to compress a bit after a few heat cycles.

I was taught way, way back to do the sequence exactly that way. And I've never re-tightened head bolts.

 

[493 Mike]

Isn't torque a measure of bolt tension?

No, It is twisting force. Either produced or required.
Mike

 

[WileE]

I was just thinking... in the category of "You Learn Something New Everyday" could someone please tell me, after I started doing this stuff over 50+ years ago, just how do you re-torque every head bolt on an engine in the car ?

 

[dvw]

Fasteners are kept tight by stretch. Torque is an aproximation of stretch. Friction affects torque. Binding threads will lower stretch. This is why lube is so important. It's also important to note different lubes require different torque values. Creeping up on a torque spec is asking for bind. That is why I use a low number, then full torque Rod fastener stretch is the most important fastener in your engine. Many high end rod companys will spec this same method. They may also tell you to torque 3 times before making the final measurement. Modern stuff is torque angle for tha same reason. Best yet is measuring stretch. Measuring stretch on a blind hole is only for someone that has very high tech equiptment.
Doug

 

[MoparLeo]

It is stretch. I f you over tighten a fastener It goes Through 3 stages.
Rigid-solid, plastic (Spring and then over stretch), fracture.
Plastic is when it is no longer in the rigid-solid stage, it starts to stretch. If you go past its tested stretch point it is no longer a spring and the metal sretches permanently. We all have felt when you over tighten a bolt and all of a sudden it get loose without breaking.
https://www.d-series.org/threads/how-to-really-torque-arp-head-studs-straight-from-arp.111485/
The Official ARP Web Site | SAE Bolts

 

[Geoff 2]

What I think IS crazy is loosening bolts...& re-torqing them once the engine has been run.
You are breaking the seal has formed.

 

[dvw]

What I think IS crazy is loosening bolts...& re-torqing them once the engine has been run.
You are breaking the seal has formed.

I do this before the engine is ever run. I did however swap a head gasket on my Cummins years ago. It would only lose coolant towing on a long run. Pressure tested never leaked even over night. Finnally decided to retorque the head. To my astonishment the very back head bolt wasn't tight. The service manual has the illustration of the tightening pattern with the back of the block at the bottom of the page. Anyway by the time I found it all the other bolts had been loosened and retorqued. That was 4 years ago. Never had an issue since. Ran it a year towing at 40psi with the loose bolt.
Doug

 

[Jeff Peterson]

I have never RE-torqued any engine fastener except header bolts since some gaskets do seem to compress a bit after a few heat cycles.

Then you've never changed an intake manifold on a Hemi!

 

[69 hemibee]

The reason for this is because it takes a bit of force to begin to move a bolt, so if the bolt is very near (but not quite at) it's final torque value the torque wrench will click and you will think you have the proper torque. If the bolt is not near its final torque then it doesn't matter.

By the way, when putting any fastener together any place where metal touches metal should be lubricated. This means the threads, but also the underside of the fastener (and washer, if present). This will give you a proper torque reading. A dry bolt will NOT give you the proper torque reading.

When lubricant is applied the coefficient of torque changes. Remember to adjust your torque based upon this. If not you will overtorque it, guaranteed.

 

[not so famous bob]

Back in the 1970's I remember re-torquing the steel shim head gaskets on a 273 build after the first cool down period after breaking in the camshaft. I did not loosen the bolts, only re-torqued them as they were.

I read online today that when re-torquing, the bolt should first be backed off a bit.

Not sure what is best. Probably boils down to who you talk to.

View attachment 1830765

never done that , and never heard that ...