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post #1 of (permalink) Old 04-26-2000, 01:18 AM
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Swapping 4.0 Flywheel into a 4.2 info needed.

Need info on swapping a 4.0 flywheel onto my 89 yj with a 4.2 and AX15. Doing the MPI swap thing. what years can I use and are all 4.0 flywheels the same. How does the flywheel index to the 4.2 crank to keep timing signals correct. Is there a difference between an automatic and manual flywheel. And does it matter what year the computer is in relation to the flywheel.. Any and all help and info will be appreciated... Thanks

Dirtybird

89 YJ 4.2, Procomp 4" Lift, MSD6a, and just gerttin started......
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post #2 of (permalink) Old 04-26-2000, 10:58 PM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

First we need to know if it is a HO or not. They number of notches on the HO is much less the the pre HO. If you are doing the Mopar kit, just do the harmonic balancer for the CPS. I bought the harmonic balancer kit thinking it would work for the non-HO MPI, but it won't. If you need the balancer, I could sell you mine.

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post #3 of (permalink) Old 04-26-2000, 11:11 PM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

unfortunatley I only could come up with a non HO 1990 head.

89 YJ 4.2, Procomp 4" Lift, MSD6a, and just gerttin started......
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post #4 of (permalink) Old 04-27-2000, 02:57 AM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

What kind of setup are using then... Any help will be nice as I would like to get it all together soon Thanks....


Dirtybird


89 YJ 4.2, Procomp 4" Lift, MSD6a, and just gerttin started......
post #5 of (permalink) Old 04-27-2000, 06:53 PM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

It is not the head that is the problem, it is the computer. The number of notches are different between the HO and non HO MPI. so the computer will not know the crank position. If you are using the 91 and later HO computer go with the balancer. If not, get the bellhousing from AA. I bought mine at No Excuses. About $80 off list.

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post #6 of (permalink) Old 04-29-2000, 10:46 AM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

Use the flywheel off a '91 or later 4.0l along with the crank sensor for a manual trans 4.0l ('91 ) to eliminate the need for the dampner kit. A wrecker will charge around $100 for both, The modified dampner will cost around $170, plus the cost of the crank sensor and mounting bracket that Mopar sells. If you are swapping in parts off a later YJ, get the sensor, flywheel and computer off the same Jeep if possible. Hope this helps, good luck!

post #7 of (permalink) Old 04-30-2000, 12:02 AM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

I am curious of the bolt pattern in the bellhousing in the '91 and later. Is that in a pattern useful to other Jeeps?

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post #8 of (permalink) Old 04-30-2000, 11:41 PM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

Will a 91 or newer flywheel bolt to a 89 4.2 crank and still be in the right timing configuration... thanks...

Dirtybird

89 YJ 4.2, Procomp 4" Lift, MSD6a, and just gerttin started......
post #9 of (permalink) Old 05-04-2000, 01:16 AM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

Yes, the 4.0l flywheel will bolt to the 4.2l the balance will be right and the timing hole in the bellhousing will work for the later EFI. The bolt pattern of the '91 4.0l bellhousing is the same as that on the earlier AMC6s and AMC V8s, where it bolts to the engine and starter. The '87 and newer Mitsubishi gear reduction starter is required if you are using this combo on a '86 or earlier Jeep, the ring gear has a different back-spacing than the earlier models with the Ford starter. Hope this helps!

post #10 of (permalink) Old 05-04-2000, 01:25 AM
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Re: Swapping 4.0 Flywheel into a 4.2 info needed.

Thanks thats what I needed to hear....

Dirtybird

89 YJ 4.2, Procomp 4" Lift, MSD6a, and just gerttin started......
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