4.0 head on 4.2 block and other swap questions

Looking to throw a 1990 Renix head and fuel injection system on a 4.2L I6. I have a brand new 4.2 short block and a 1990 4.0XJ with a seized crank at my disposal. It's all going into an FSJ that had a carb'd 258 at one point. I would like to use as many parts that I already have on hand as possible but will do whatever it takes to make it work.

Should the 'ECU' be able to handle the extra 0.2L? Also, what all wiring will need to come out in order for me to swap the fuel injection system over? Can I run the 4.0 distributor on the 4.2 or is that apples and oranges? I will be running an AX-15 but the Jeep that is donating the parts has an AW4, wil this cause any problems? If I remember correctly there is a hole in the tranny bellhousing for the CPS, I'm guessing I will need to run a 4.0 flywheel rebalanced to a 4.2?

I'm assuming that the alternator will need to be swapped as well.

Anything else I might have overlooked?

Thanks for the help!

JP Magazine put a 4.0 in a FSJ.

Here is a link to one part of the series: http://www.jpmagazine.com/projectbuild/154_0904_1968_jeep_j2000_project_j2008/index.html

A little searching on their website and you can find the rest of the series.

Thank you so much!

Zoro said:

Thank you so much!

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aaron barnes is trying to contact you via PM but the system reports your in-box is full. You need to delete some stuff.

The flywheel will swap over, no need to re-balance. The distributor will also work, so you shouldn't have any problems. You will have to block off the Mechanical fuel pump hole in the block, and swap over the Harmonic balancer from the 4.0. Should be pretty straight forward. The extra .2 liters (200 cc's) won't be an issue.

joe_peters said:

aaron barnes is trying to contact you via PM but the system reports your in-box is full. You need to delete some stuff.

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Yes I had 127 out of a maximum of 100 ??? All fixed now

Team Willys said:

The flywheel will swap over, no need to re-balance. The distributor will also work, so you shouldn't have any problems. You will have to block off the Mechanical fuel pump hole in the block, and swap over the Harmonic balancer from the 4.0. Should be pretty straight forward. The extra .2 liters (200 cc's) won't be an issue.

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Cool!

On the Renix setup how does the CPS tell where the engine is? Magnets on the flywheel? That was my main concern.

"windows" -- holes in the outter ring of the flywheel/flexplate that pass by the CPS and tell it orientation.

I did this swap on a wrangler a couple years ago and could never get the setup to run properly for more than a short time. I ended up using an HO conversion kit from Hesco http://www.hesco.us/ which worked with the Renix head. If you make it work share with us how you did it. Make sure that you fill the water passages and use the 4.0 head gasket. There is a decent article here: http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=277013 that includes info on building a hybrid 4.2/4.0

Honestly though, I would take a hard look at doing an HO setup instead of the Renix.

REVROK said:

I did this swap on a wrangler a couple years ago and could never get the setup to run properly for more than a short time. I ended up using an HO conversion kit from Hesco http://www.hesco.us/ which worked with the Renix head. If you make it work share with us how you did it. Make sure that you fill the water passages and use the 4.0 head gasket. There is a decent article here: http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=277013 that includes info on building a hybrid 4.2/4.0

Honestly though, I would take a hard look at doing an HO setup instead of the Renix.

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Ideally I would go with the HO setup but I have a Renix Jeep at my disposal and I really can't argue with the price.

One question for today, where the heck is the 'ECM' on a 1990 4 door?

I will keep you guys posted!

The crank position sensor is the killer. I am not sure if this is an issue on the Cherokee... someone help he and I on this since my familiarity with this swap was on a Barbie Jeep? Isn't the CPS in the rear of the block on a Cherokee? OK, just found a good diagram on this page... http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm . It is mounted in the bellhousing and may or may not work with a 4.2 liter block. I would call the folks at HESCO for as much advice as you can get (they have always been very helpful to me). Everything except the the CPS will work beautifully with the conversion, but it was using a Wrangler HO CPS for the Wrangler that kicked my b*tt, I would get it adjusted and it would run for a short time and then gone.

OK, I am looking at the earlier posts and it seems you may be okay! So much for my reading skills! I would definitely use that link above though. It should be very helpful, in fact that site looks like a great help for you.

I had a plan to do this exact swap on an FSJ (83 Cherokee). There will be a clearance issue between your brake booster and the 4.0L intake manifold. The only way I found to make it work was to use a Hydroboost set up for the brakes.

IFSJA.org has some good info on this swap.

Zoro said:

One question for today, where the heck is the 'ECM' on a 1990 4 door?

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under dash between Instrument cluster and heater core box

Thanks guys!

IFSJA has mountains of good info.