Re: [Amc-list] Torqueing head - bar torque wrench okay?

[Frank Swygert <farna@xxxxxxx>]

TSM says 58-62 for the head bolts, so 60 is a good number to aim for. 

The proper procedure for re-torquing is to back off about 1/2 turn (just enough to crack it loose) then tighten to spec. The reason is a bolt can stick in the hole or the threads can stick, requiring more torque to get it to move than the torque spec. In Tom's case, where the bolts were very recently removed and threads cleaned, it should be fine just to see if they move by tightening without cracking loose first. If the bolts have been in for a while they MUST be cracked loose first. A stuck bolt might take 80 pounds to break loose but only have 40 pounds of holding power. 

The bolts work loose over time due to thermal expansion/contraction. I'm sure the age and quality of the metal the bolts and block are made of has something to do with it also. AMC used a slightly higher nickel content iron even back then, but there are other qualities that make a difference. Could just be the way it was cast, and the thickness (or lack of) around the bolts. In any case, if they aren't retorqued on a regular basis it will end up like Tom's junkyard donor and a blown head gasket. If run hot enough or repeatedly it will warp and crack. 

The schedule I recommend is every 12-15K miles, every other year, or if the valve cover is off for some other reason has worked well for me, drove a 196 for 14 years using that schedule with no head problems. It was my "second car" (wife's was the first) and I put 5-7K on it yearly during most of the time I owned it. Not the two years I was in Japan, didn't take it with me, just used it when home on leave in the middle of the tour. That's still 12 years of steady service.

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Date: Thu, 27 Mar 2008 13:12:07 -0700 (PDT)
From: Tom Jennings <tomj@xxxxxxx>

>  Also, when torqueing - you back off the bolt a little bit first, then 
torque it, right?

I didn't/don't. I have little experience with this motor and the 
head-donor in the 'yard... mine, I took the head offwithout checking 
torque, but they were all fairly tight and even enough. When I retorqued 
it a few months later it was all tight (none budged).

The junkyard donor -- that had the ventilated block -- now when I took 
those head bolts out, the torques were all over the place! About half of 
them were LOOSE! "Snug", but definitely not 40 or 60 ft/lbs (whatever 
the TSM says it is).

-- 
Frank Swygert
Publisher, "American Motors Cars" 
Magazine (AMC)
For all AMC enthusiasts
http://farna.home.att.net/AMC.html
(free download available!)

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