Re: [AMC-list] 258 crankshaft differences

[Jim Blair <carnuck@xxxxxxxxxxx>]

The breakdown goes like this: '71 is all by itself (small bell block and flat flange like earlier 199 and 232) then '72 till about '78 is the heavier crank with the most balance weights. '79ish till the plastic valvecover in late '81 was partially lightened and the lightest was '82 to '88 but they all interchange (except the '71 crank flange)
   The heavy crank is desired by the offroad crowd because of its inertia for climbing. The piston design changed at the same points, but its compression ratio more than anything. 
   I think the combustion chamber size increased at those points too. I stuck a small chamber head on a motor with flat tops and it smoked like crazy but ran like a bat out of hell till the pistons cracked. 
   Thankfully the 6 cyls are all zero balanced. 

From: russ hathaway <russh97309@xxxxxxxxx>
To: Rambler Nash Jeep and familyAMC <amc-list@xxxxxxxxxxxxxxxxx>
Subject: [AMC-list] 258 crankshaft differences
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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

 		 	   		  
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