| MOXIE | -- 10-22-2009 @ 2:55 PM |
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If 35 to 40 pounds torque is all that is required for aluminum heads to not leak, why do steel heads have to be torque to 60 foot pounds.
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| Chevguy49Ford | -- 10-22-2009 @ 4:33 PM |
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I would imagine it is due to the aluminum heads expanding more and quicker with the engine heat. If they were torqued like a steel head I think the head bolts might snap. Cheers, Scott. 1949 Custom Tudor. http://i36.photobucket.com/albums/e42/35thLE/49016.jpg
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| supereal | -- 10-23-2009 @ 8:44 AM |
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The softer material in aluminum heads can't withstand the higher torque without causing excess distortion. The torque readings can be skewed if washers are placed under the head nuts, or the nuts are oiled before they are tightened. Along with electrolysis, overtightening also contributes to the difficulty in removing the heads.
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| 39 Ken | -- 10-23-2009 @ 2:12 PM |
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Super, Please elaborate on your last post. It is recommended by Ford and others; ie. Offenhauser, Edelbrock, etc., that a hardened washer be used with bolts or studs on aluminum heads/manifolds and from my experience, lightly oiling the nut or bolt interference with the washer insures equal torque values with all the studs/bolts/nuts or what have you. Thanks, Ken
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| 37RAGTOPMAN | -- 10-23-2009 @ 3:21 PM |
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besure NOT to use copper head gaskets when using ALUMINUM HEADS, if you want higher compression heads on a 24 stud motor, use 38 and up truck heads these are castiron,and I believe they are 7.5 heads,these are the 95hp engines,you might have to do a little reserch, but I have heard about this, hope this helps,37RAGTOPMAN
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| supereal | -- 10-24-2009 @ 10:36 AM |
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Ken: Washers under the head nuts are often recommended by the makers of aftermarket finned heads, IF they are hardened, as you say. That said, they do alter the torque wrench reading a bit from the factory specs of 35-40 for aluminum, and 50-60 for iron. We prefer to chase the stud threads and install the nuts dry,without washers on iron heads, or better yet, replace the studs to prevent breakage. Years ago, we Ford mechanics didn't use a torque wrench, but had long T handled extension wrenches with which we tightened the nuts by feel. No problems resulted, so it seems torque readings aren't critical, as long as they are not overdone. Today, with aluminum heads the rule, rather than the exception, on newer vehicles we have to always use new head bolts and strict torque tightening. Some bolts are tightened with a special wrench that measures how far to turn to regulate the stretch of the bolts. Our old cars are not that critical.
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