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4.0 with 4.2 crank

Swaping 258 to 4.0, 4.0 parts to 258 etc!
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Billy
Posts: 1
Joined: September 7th, 2021, 3:37 pm
Vehicle Year: 1988
Vehicle Make: Jeep
Vehicle Model: Wrangler

4.0 with 4.2 crank

Post by Billy » September 7th, 2021, 4:14 pm

I've been looking at some pages for some information on putting 4.2 crank in the 4.0 block. From what I'm gathering it can be done using the 4.0 piston. Question is do I use the 4.0 rods or the 4.2 rods. It's a offroad only toy and just looking for a little more power. Thanks in advance for any help.

275/350 I-6
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Making Progress
Posts: 55
Joined: February 4th, 2020, 8:48 pm
Stroker Displacement: 4.7
Vehicle Year: 1985
Vehicle Make: AMC
Vehicle Model: CJ-7
Location: NC

Re: 4.0 with 4.2 crank

Post by 275/350 I-6 » September 17th, 2021, 7:19 am

You can swap the 258 crank & rods using the 4.0 piston, but the compression and quench will not be optimal. You will have to run high octane gasoline. Most people replace the pistons to get over this problem. I replaced the pistons & rods from Russ Pottenger, along with everything else to build an awesome engine that runs on 87 octane gasoline.

I suggest you talk to Russ before you do anything.

Check out this site for more info on stroker recipes.

http://www.jeep4.0performance.4mg.com/stroker.html

Contact Russ at (626) 967-1000 Bishop-Buehl Racing Engines for first hand experience.

https://www.engineere.com/US/West-Covin ... ng-Engines

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