January 24th, 2017, 12:05 AM
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-= Extreme Supporter =-
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Join Date: Jun 2013
Location: Greer, SC
Truck: 1964 GMC 1500 2wd
Age: 70
Posts: 471
Thanks: 26
Thanked 13 Times in 9 Posts
Rep Power: 215
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Re: 478M Loosening Rod Bolts
Quote:
Originally Posted by 1972RedNeck
So I have a line on the front half of a '74 GMC 8500 with a 478M, five speed, and four speed OD brownie. The engine has had multiple fresh rebuilds. Apparently, after the first rebuild, one of the rod caps came loose. They pulled the pan, put a new bearing in it, and torqued it back to spec. It came loose again, and another time.
It was torn completely down and all new rods and pistons were put in. And it shortly thereafter developed a rod knock and was parked.
What do you all think could be the problem with it? The price is right, but I don't really need something that I can't fix either...
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I wonder if they check the sizing of the new rods before they installed them. I would resized the rods to fit tighter on the bearings and maybe install a dowel pin in it to lock the bearing in place (like some of the racing engine mechanic do to their engine).
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