The Serious FresheningGo to <Last, Summary, Next>Engine—New Head Bolts
Completed: 2007-11-17 — Started: 2006-01-26
Work Completed: In late January, 2006, Lynn contacts Restoration Supply Company and inquires about replacements. Lynn is told that RSC is temporarily out of the size he needs, but that they will be ordered. It will not be until July that RSC is able to deliver these bolts. In the meantime, Lynn buys grade-8 7/16"-14 x 3" bolts from his local hardware store. These bolts are a little too long for a few holes as the bolt appears to bottom. Lynn grinds ~1/8" off these bolts. Also, the top of bolt at the extreme forward position on the head is tight up against the thermostat housing. It isn't possible to get a thin walled socket over a 5/8" headed bolt in this position. (This is a second indication that the 9/16" headed bolts were original.) Initially, Lynn uses the sole remaining 9/16" headed bolt that he got with the car in this position. However, it too eventually snaps, but the stub is easy to remove. Lynn uses a grinder to cut a little more space in the thermostat housing around the bolt head. After these modifications the grade-8 bolts work great and the only unsatisfactory aspect is that the head (too slim, wrong color, strength marks) is not period correct for the vehicle. (Anticipating his growing impatience, RSC supplies Lynn chrome acorn caps in June to hide the strength marks on his OSH grade-8 bolts. The chrome finish is also not period correct, but it looks way better to most people than the grade-8 head.) In September, Lynn decides to install his new RSC high head bolts. At 50 ft-lb of torque, his first stop on the way to 65 ft-lb, several of the bolts stretch and one snaps. Yikes! Fortunately, the stub of the broken bolt is fairly easy to remove from the block after drilling and use of an E-Z-out bolt extractor. U.S. Bolt Torque Specifications for 7/16"-14 Bolts
Lynn uses copper gasket sealer to coat all the threads (as the holes penetrate through to the water jacket) and this could easily qualify as a lubricant on the threads. Lynn is surprised to learn that the torque specifications for lubricated threads are much lower than for dry threads. The stretched/snapped bolts at 50 ft-lb imply to Lynn that the strength rating of these bolts is probably a S.A.E 5 or 6. In November, 2006, Lynn orders a second set of high-head bolts from RSC. He torques them to about 35-40 ft-lb, his current recommended torque for lubricated Kissel head bolts.
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