Re: 38 Twelve loose crankshaft pulley
Posted by Peter Packard on 2021/4/20 3:02:00
Hello all, Very appreciative of the input and I would like to provide a bit of detail in how I am convinced that I have resolved the loose crank pulley for others that may encounter the same problem.
Packard 12 engines are not cheap to do anything with...a $A40k potential problem.
Well, the pulley crankshaft bolt inch and seven eighth, seven eighth UNF 16tpi together with the crank thread were stripped as the bolt had topped out on the crank without the pulley being tensioned, possibly due to working of a developing clearance There was no way to make an original bolt work and a NOS bolt was doomed to fail. The original bolt has a 1.75 AF ( across flats) dimension and I defy anyone to get a socket behind the radiator shroud.
I was not prepared to do a front clip removal on the Twelve ( have done 120's and 25th Series) and decided to remove the lower approx 12 inches of the shroud and it is replaceable although the skin on my knuckles from the grinder will take a little longer. The original 1.875 bolt, .825 inch 16 TPI was 1.25 inches in length. I have manufactured a 13/16th AF 2.15 inch in length bolt of the same thread dimensions and a cup washer of 0400 inches, recessed .25 inch to allow it to press onto the pulley rather than bottom on the crank. there is 1.75 inches available in the crankshaft. I fitted this and also locktighted the arrangement. I have driven it approx 100 miles and it appears to have resolved a faint but "bound to get worse" noise. Twelves are quality products and are meant to be very quiet.
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