Re: [AMC-list] 258 crankshaft differences

[Frank Swygert <farna@xxxxxxxxxxx>]

Date: Mon, 25 Mar 2013 20:24:18 -0700 (PDT)
From: russ hathaway<russh97309@xxxxxxxxx>

What year did AMC switch crankshaft designs? They had the big counterweights in the early years, then went to smallers weights towards the end. What year did they switch over?
I have a 1980 258 in need of a bottom end and a good 83 crank......Russ
=================================

The change was early in 1980, around the end of January, so early 1980 model year vehicles have the 12 counterweight cranks, late 1980 models the four counterweight (and about 20 pound lighter) crank.

The cranks interchange -- all 199/232/258/4.0L cranks will interchange with no problems. Jeepers report no more broken "light" cranks than heavy ones, so strength isn't an issue. Some prefer the heavier one because it should be stronger, but in reality the lighter one is strong enough. The only practical advantage to the heavier crank is that it's better for a rock crawler -- the heavier rotating mass is harder to stall. Likewise the lighter crank will spin up a fraction of a second faster.

--
Frank Swygert
Editor - American Motors Cars Magazine
www.amc-mag.com

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