Does anyone know where I can find an amc 258 crank?!

[Tophipe]

So long story short, the PO did something really funky with the crank. When I pulled the flywheel while changing my clutch all six crank holes pulled the threads out. My local engine builder/machinist said he'd never seen anything like it, but what had probably happened was they stripped it out some on install, so there just wasn't enough material after they were pulled and they slipped. I drilled the crank out, tapped it, helicoiled it. All but one of the helicoils worked okay, but one of them kept slipping. The problem was that the bolt had created a groove in the back of the hole that was larger than drill, so the helicoil wouldn't hold tension in the back and would pull itself out. Not much I could do to fix it. Now I'm looking to just replace the crank but am having a hell of a time finding one. Oreilly, autozone, and advanced auto all list a remanufactured crank by crankshaft rebuilders on their site, but all of them have it listed as unavailable. Do you think they could still special order it for me? Northernuto also has the correct crank; however, they want about 100 more than the others and there is a 200 dollar core charge as opposed to the others which is about 30. I've also tried looking on ebay, but it's pretty bare out there. Any info you guys have would be deeply appreciated!!

*This is for an '83 AMC 258 i6 / 4.2l by the way

Edit: Looks like Summit doesn't have anything either

 

[Peanut Butter]

One source: NEW 4.2L CRANK SHAFTS PN:HES9-4.2L-3895R | Hesco Rod

 

[Dan77CJ7]

i might try putting some Jb weld at the bottom along with the heli, let it set up for a day or so, its worth a try if ur willing to buy a new one?

 

[ThisGuyUKnow]

dang you are a day late and a dollar short! I had one a week or two ago that got tossed with a junk engine.

 

[IOPort51]

I am surprised your engine builder can't find a serviceable "core" from one of the local suppliers.

 

[tinman]

I've got an engine that I planned on pulling the guts out for a stroker, but if you could figure out how to get up to Idaho Falls, I could sell it. It had a cracked block, but I ran it for a couple years that way, ran great and didn't smoke at all. I could even get it to Boise if needed.

 

[Bent]

Any crank out of a AMC 258 i6 / 4.2l or AMC 258 i6 / 4.2l will work. 1983 was the first year for the "light weight" crank. So any thing up to the end of production in 1990 will have the same 4 counterweight crank shaft that you have now. Some do have a longer snout, but you can use the same harmonic balancer with spacer.

I would suggest finding a 12 counterweight crank out of a pre 1983 AMC 258 i6 / 4.2l . Get the flywheel also. This combo is about 30lbs heavier than the lightweight design. That's a lot of rotating inertia. With the high compression head and pistons that you already have, you will end up with a great low rpm torque motor.

 

[Tophipe]

Yeah I was looking at these, is there a difference between these and the scat? @Peanut_Butter

 

[Tophipe]

Any crank out of a AMC 258 i6 / 4.2l or AMC 258 i6 / 4.2l will work. 1983 was the first year for the "light weight" crank. So any thing up to the end of production in 1990 will have the same 4 counterweight crank shaft that you have now. Some do have a longer snout, but you can use the same harmonic balancer with spacer.

I would suggest finding a 12 counterweight crank out of a pre 1983 AMC 258 i6 / 4.2l . Get the flywheel also. This combo is about 30lbs heavier than the lightweight design. That's a lot of rotating inertia. With the high compression head and pistons that you already have, you will end up with a great low rpm torque motor.

I found one of each of the cranks so this might be an option. I do have a nice new flywheel for the 83 though

 

[Tophipe]

I am surprised your engine builder can't find a serviceable "core" from one of the local suppliers.

Yeah I think the issue is that I live in Crawler territory so everyone and his mother strokes their 4.0's before doing a transplant

 

[Bent]

I found one of each of the cranks so this might be an option. I do have a nice new flywheel for the 83 though

The 1983 flywheel will work. Not quite as heavy though. I've been told the AMC 304 and the pre 1983 AMC 258 i6 / 4.2l use the same flywheel. I don't have any casting numbers to back that up with though

 

[Andre LeMoine]

Have you thought about using a time-sert. It's a sleeve instead of a coil. Red loctite it in. Call some automotive shops in your area to see if they use them. It's an option. On a shallow hole it will stay put better than a heli-coil.

 

[IOPort51]

Have you thought about using a time-sert. It's a sleeve instead of a coil. Red loctite it in. Call some automotive shops in your area to see if they use them. It's an option. On a shallow hole it will stay put better than a heli-coil.

these are totally cool! they are also rather expensive.

 

[Tophipe]

The 1983 flywheel will work. Not quite as heavy though. I've been told the AMC 304 and the pre 1983 AMC 258 i6 / 4.2l use the same flywheel. I don't have any casting numbers to back that up with though

I'll be going to JWjeep in Sac to pick up some parts along with my crank. They have both the 12cw and 4cw cranks in stock so I'll be able to compare them in person along with the flywheels