Head Torque spec's Help

[drmiles]

Ok not a Hummer question, But I am helping my son change head gaskets on 98 chev z71. The torque specs say 22 ft lbs then add'l 45 deg for short bolts, 65 deg for med bolts, and 75 deg for long bolts. (degrees from memory will check book again for exact)

Question
1. my Torque is in inch pounds. Is it a simple conversion 12 in lbs = 1 ft lb?

2. Is there a degree wrench or do you just estimate the number of degeree's to tighten??

Thanks
Jerry Miles

[Humdingah]

You are correct...1 ft.-lb. is the equivalent of 12 in.-lbs.

22 ft.-lbs. sounds low for head bolts...

And they do make add-ons for wrenches that will measure degrees...I've seen analog dial ones from Snap-On and I've seen digital ones but I cannot remember who made the digital ones.

[drmiles]

Agreed 22 ft lbs is not very tight. Either I am reading this book wrong or the book is wrong. Will try to search the net for info.

Thanks just wanted to make sure I am on the right track before I mess up something.

[drmiles]

Found this



Best Answer - Chosen by Asker

Whatever you do, don't follow the recommendation of llac_queen. They obviously have some learning left to do. No car or truck ever made has a cylinder head torque spec that low.

Here's the full procedure;
Install the bolts in sequence to 22 ft. lbs. (see pic in link) The bolts must then be tightened again in sequence in the following order:

a. Short length bolts: (11, 7, 3, 2, 6, 10) 55 degrees.
b. Medium length bolts: (12, 13) 65 degrees.
c. Long length bolts: (1, 4, 8, 5, 9) 75 degrees.

You can find a picture of the initial sequence here:
http://www.autozone.com/images/cds/gif/m... (http://www.autozone.com/images/cds/gif/medium/0900823d8010ef7e.gif)

P.S. the manual recommends using thread sealant on the bolt threads. They probably go into a water jacket.

10 months agoSource(s):

Chilton's SUV Service manual 2002
Professional Technicians Edition, page 13-8

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[HUMTECH]

That sounds correct, they are a torque to yield bolt. Once done the final two passes with a torque angle gauge they will be ok. A torque to yield is much more accurate than simply torquing to a specific ft lb number. You should also replace all the head bolts, normally a one time use. When they are torqued the bolts actually stretch to achieve the max clamp load they are designed for

[HUMTECH]

Just looked up the service procedure and gm does not say to replace the bolts.

[drmiles]

bought new bolts, don't want to do this again. Ordered a angle wrench. seems like guessing should be enough, but the wrench is coming.

[drmiles]

on the second torque do you follow the same order or do you do all the short, medium then long bolts?

http://www.autozone.com/Action,specsSelect/N,23200244/addVehicleId,2389603/shopping/specsSelect.htm

[HUMTECH]

Yes, in the same sequence. A little trick i use is once your done the initial torque mark all the bolt heads with a paint pen in a vertical line, that way you wont miss a bolt or over torque one, once the line you made is not vertical you know that one has been torqued.