shims under the jugs on a 5 star

M.Genrich

Member
I bought a tough looking 5 star today That has a stack of shims under the jugs that Im guessing to be better than 1/4 thick. The old boy I bought it from said that in the early 70's he had it overhauled with 670 jugs and 4 3/4 M&W pistons and put on two new 4210 heads. Whats the story on the shims? I freshened up a ub a couple of years ago with the big jugs and pistons. What is different on a 5 star?
 
Spacer plates under the jugs are used to get the compression right in the engine. If I had to guess, I'd say that when it was built originally, the compression was higher than what they wanted, and the cheapest/easiest way to fix that is spacer plates under the jugs.
 
The rods in the MM 283 motors are too long to simply install M5/670 jugs and pistons. And, the 283 cannot use the shorter M5/670 rods. Some people used double gaskets and some used spacers when they upgraded their motors to keep the pistons from contacting the head.
 

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