12wt 4.2 crank AND caps??

Performance mods and Advanced Stroker discussion.
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12wt 4.2 crank AND caps??

Post by [email protected] »

I researched this (and many other) forums for this answer, if it's been answered (I see the same questions, no answers) please be kind as to send me the post link and disregard.

I have a 4.2 12wt crank, 4.0 rods, and wrist offset/.020 over Icon pistons to make it all mesh. I understand the 4.2/4.0 main bearing differences, and that I should use my 4.0 caps and bearings.

That being said, I'm putting in an extremely heavy crank combined with more power and displacement, all while being forced to give up the girdle for my main studs. The 4.0 hollow caps are chewing at my mind as the probable weak point. If I use 4.2 main caps and have it align honed, would this be acceptable/even work? Do I use 4.0 bearings block side with 4.2 bearings cap side if it does? I feel like the question "is it even possible" has not been answered, I've read a few talking points but no successful followup posts.

With that being said, am I just being ridiculous? Are the 4.0 caps known for failure with the 12 CW crank? It really makes me wonder if they felt comfortable with hollow caps 91+ because the crank was lighter. Has anyone ever had a 4.2 12 CW crank break a 4.0 cap? Someone with thousands of miles on a 12 CW crank in a 4.0, please chime in! It feels like I'm leaving something out on the bottom end, I will source 258 caps if the general consensus is that it makes a difference. Building a bulletproof block here, spare no expense.
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Re: 12wt 4.2 crank AND caps??

Post by Cheromaniac »

I sold my '92 XJ more than five years ago with 86k miles on a 4.6L stroker that I built with a 12cwt crank. It was still going like a raped ape so you needn't have any fears about the 4.0L block main caps.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :mrgreen:
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Re: 12wt 4.2 crank AND caps??

Post by IH 392 »

The 12cw crank has LESS harmonics than the other cranks, the only reason they went away from them was cost of materials savings.
the bottom end of the AMC/Jeep six is a very stout block, the lighter main caps of the 4.0 will hold up just fine, and you can use the main girdle with spacers to move it away from the long crank.
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