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Old 05-01-2009, 09:51 PM
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head torque specs/angle torquing

Long story which I won't get into now, but I have to replace a head gasket on a 2003 buick SC 3800 (Park Avenue) without an angle torque wrench.

Alldata says 37 ft-lbs and then 120 degrees. i don't have a degree wrench, nor can I get my hands on one before I need to do the job (and I refuse to spend more on the wrench than I did on the car)

What do you think. 60 lb-ft? 70? 55? What was the torque spec on the older ones before they did the angle-torque stuff? Bolts are 7/16"

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Old 05-01-2009, 10:18 PM
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The torque-to-yield aspect, as you have correctly assumed is in the bolts. Good idea to swap back to the earlier ones prior to that method. Most all 7/16" head bolts and main bolts are 70 ft.lbs, whether its Chevy, Dodge or Ford. You should be safe torquing them to that.
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Old 05-01-2009, 11:08 PM
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I've never done that kind of torque before but 37 pounds plus 120 degrees would be 37 pounds plus 1/3 of a turn. If the bolts are normal 6 sided heads, just use a magic marker and mark off 1/3 of one rotation on the head surface/bolt head (2 flats on the head) and turn the extra 120 degrees. Not dead on but will get you within a couple of degrees.

Or I could be completely out of whack on this stuff! LOL

Mark
(loves Brussel sprouts!!!)
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Old 05-02-2009, 01:55 AM
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Thanks for the help... and I LOVE Brussel Sprouts. Its the Lima Beans that haunt my dreams.

I think I'll shoot for a combination of the two. I'll torque them to 37, mark them, then reset my torque wrench to 65 lb-ft. I'll turn them until I get to 120 degrees or 65 lb-ft, which ever comes first.

I chased the threads and they were squeaky clean, so I'm confident that any torque values will be accurate.

Thanks
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Old 05-02-2009, 05:33 AM
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OEM p/n 25424 is an inexpensive 1/2" drive angle gage that is used w/your breaker bar/torque wrench.

What I do is use it to determine the torque of a bolt using a beam-scale torque wrench.
Subsequent bolts are then torqued to that spec w/a regular torque wrench.

On the bolts I was working with, torque plus degrees amounted to 55 ft/lb. on the beam. Set the clicker to 55 and let 'er rip.
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Old 05-02-2009, 10:56 AM
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I was doing some searching last night and found one resource that confirmed the 37 + 120 degrees, but also added that if you reach 60 lb-ft before you get to 120 degrees, stop.

Maybe I'll just set for 60 and call it done.
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Old 05-02-2009, 11:34 AM
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Torque for a 7/16ths grade 8 oiled bolt is right at 60 lbs.......75 dry.
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Old 05-02-2009, 11:35 AM
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im building a 1995 3800 right now its the L36 NA one and i just torqued to 37 and turned the breaker bar on each one 120 degrees more. it feels like its so tight the bolts might snap, but thats to make them so tight they stretch slightly. one once they have been stretched then thats all they can ever be used, its crazy but its how it works.,


how we always do these, no angle meter fancy mabob thingy.

have done many head jobs with torque to yield bolts like these

including ford 4 cyls and many other gm v-6 such as 3.1 and so on

just razor blade clean the engine decks and the heads and oil the bolt heads with some engine oil etc. and go to it. the threads usually alreadyhave some sealer/locker on them. if not then use something like plumbers pipe thread dope to seal lube them




easy

never any issues
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