AMC 258 crank has a longer nose than the 4.0?

[W_A_Watson_II]

I've read that the AMC 258 crank has a 1.0cm longer nose than the 4.0 crank, is this true? And if so how important is it to install a spacer placed in front of the crank pulley ensures that it won't walk forwards and throw off the serpentine belt?

Will

[IH 392]

Yes, the "V" belt cranks do have a longer snout, the serpentine 258's have the short snout, you need to have the spacer or shorten the snout or the dampener can walk it need to have the tension from the bot holding it in place.

[Cheromaniac]

I've read that the AMC 258 crank has a 1.0cm longer nose than the 4.0 crank, is this true? And if so how important is it to install a spacer placed in front of the crank pulley ensures that it won't walk forwards and throw off the serpentine belt?

Will

The 12-counterweight 258 cranks made from '72-'80 and the 4-counterweight cranks made from '81-'86 do indeed have a 1cm longer nose than the 4.0 crank. Just have the rearmost 1cm sliced off an old 4.0L harmonic balancer with a lathe and use that as a spacer in front of your new 4.0L harmonic balancer.

[W_A_Watson_II]

Thanks guys, looks like I need to get/fab the 1 CM spacer.