I am replacing head gaskets on an 83 Ford LTD with the 3.8 V6. I am using new Fel Pro head bolts, but when I try to bring them sequentially up to the final torque value of 74 ft lbs some start stretching. The manual says to put pipe thread compound on the short bolts (ones going into water jackets) and lightly oil long bolts. I have done this. What is the solution to my problem? I am using a beam type torque wrench.

 

If you feel the bolt continuing to turn before reaching rercommended torque value, either the steel in the bolt is yielding, or, the head gasket is not supporting the bolt load adequately, and may be "squishing" out, or the threads in the block are yielding. The third thing would be the worst.

Take one of the bolts, place a good strong spacer on it, or in a drilled hole through a thickness of steel of proper length to allow putting a nut on the threaded portion, with the spacer being "tightened" by the nut. Clamp the nut in a strong vise, then apply torque to the bolt head. If the bolt is NOT inferior, it will torque right up to value, and resist further rotation of the bolt head. If this confirms the bolts are adequately strong, check threaded holes in block, if OK, buy a different type of head gasket and try again. Be certain your bolts are not of the "use only once" variety. It is unlikely a beam type torque wrench would overtorque at indicated value by enough to yield the bolts.

Let us know how this turns out. imp

Edit: Check also that the area of the head immediately surrounding the head bolt holes, is not being crushed, crumbled, cracked, or visibly deformed, especially possible if of aluminum.

 

Thanks! That is an excellent idea. I will try that. Interestingly, one of the bolts actually stretched so much it was an 1/8 of an inch longer than a new unused one. It also was thinner along part of its length and the threads actually looked wider apart. Very elastic! I am lucky I stopped turning on it before it broke. Two shop manuals for this engine stress using new head bolts whenever the heads are removed. I thought Fel Pro was a premium product. At least their gaskets have been used in the performance market.

Does this complete removal of just one bolt mean I should start completely over with my tightening sequence? The manual says to progress from 47 to 55 to 63 to 74 in typical center - out order. It also says that after the initial tightening I should loosen each bolt two turns and go through the sequence again. What a pain!

 

It sounds by your description that the bolts are of inferior strength, no problems with gasket, block threads, or head. Probably imported bolts or the steel used to make them, do not meet strength specifications.

You can determine the bolt size, length, and thread type (coarse or fine), and order Grade 8 bolts from a reputable supplier. I would guess they are metric.

Or, buy someone else's bolts, try NAPA, tighten one or two as I described, not quite to torque spec, in the vise, and note how "solid" they feel at that torque level (maybe 10-15 ft-lbs below called for max). If they seem OK, replace the old ones, remove them one by one, replacing with new, as you torque to maybe 90%. Get them all in, final torque them, you might just get away with nothing more, using gasket already in place. Worth a try. imp

 

One of the reasons I DON'T own a Ford with this engine is the long, long history this engine has with overheating and blowing head gaskets.
To save any trouble with this, get yourself some headgaskets and NEW bolts. They are Torque to yeild and are never to be reused, or you'll be doing it over again.
Also, engines with aluminum heads will always feel a little on the 'loose' side when torquing it down, just due to the relative flexibility of the metal (or, at least to my calibrated elbow).