need some help.

[mark.deady]

i have a 1987 mj with a renix 4.0 and a auto trans. i have a rod knocking so it needs a heart transplant. i picked up a 1997 4.0 out of a wrangler for 250. it has 80k in it. what do i need to do to put it in my jeep. i have looked into using the stock renix head on the ho block but then i hear everyone is converting to the ho head on the renix block. i am wondering what is involved with just keeping the ho head and intake. the motor was complete as well with fuel injectors, rail, ps pump, alt, ac comp, and header. thanks for all the help.

[mvusse]

To swap the whole thing you need engine bay wiring harness, dash wiring harness, computer, fuel sender, dash gauge cluster and splice in the old tail light harness to the new dash one.

 

To use the long block you will have to move all sensors over from the old one and drill/tap for the knock sensor (didn't somebody say recently the boss is there in an HO block, but not drilled?). The HO head does flow better than the Renix one, but with the head you will have t swap the intake and exhaust manifolds as the ports won't match up otherwise.

 

 

disclaimer:

Even though I have both Renix and HO 4.0s in my vehicles I have never yet had either apart that far to verify. All this information is what I remember from posts in the past. Hopefully someone else will chime in to either verify ^^^^ or correct it.

[TrailReadyMJ]

Well, you will get more answers in the tech section, but here is my input....

 

You really have a few choices on how to go about this.

 

1. As mentioned, swap absolutely everything from the TJ. Make sure you get everything from the donor TJ you need or the little things may nickle and dime you to death.

 

2. Run the HO head and Renix manifold. Technically there is a port matching issue on the intake manifold, so many frown on this route. The difference is not tooo drastic, and I am currently running this setup until I can do option 3. I was going to change it ASAP, however I keep putting it off because it runs good and gets decent mileage. It's actually at the very bottom of my "project list".

 

3. Run the HO manifold, TB, fuel rail, and injectors. The HO TB will need to be modified for the renix TPS, but this can and has been done. http://www.jeepforum.com/forum/f11/renix-ho-tps-307608/. There are better write-ups on this, but this was the first thing that popped up when searching. I plan to go this route eventually by using the 99+ intake.

 

The main reason I opted for #2-3 is simply because I don't like Chrysler electrical, and am partial to the ol' renix stuff... opinions vary :D Also, I didn't have a full donor for the swap, just the block and head.

 

IMPORTANT NOTE! If you swap in a HO engine, but opt to keep the Renix injection, you MUST use the Renix flywheel/flex-plate!!! Otherwise the CPS will give false readings and it won't start.

 

Also, the HO does have a spot for the knock sensor, and it's already threaded (at least mine was, 93' block) so no problem there. The temp sensor for the fan moves to the T-stat housing instead of next to the knock sensor.

[mjeff87]

ToTo use the long block you will have to move all sensors over from the old one and drill/tap for the knock sensor (didn't somebody say recently the boss is there in an HO block, but not drilled

 

that would be me, but I haven't gotten down to my storage place to verify yet... :oops: Sounds like TrailReadyMJ has verified tho :cheers:

 

One other small overlooked detail is that the cooling fan is center-mounted on TJ/YJ's whereas MS/XJ's are offset. You'll have to swap all of your MJ front accessories/brackets, including possibly the water pump, to the TJ block to get it all to line up in your MJ.

 

I learned this the hard way swapping an XJ 4.0 into my neighbor's YJ last year.

 

Jeff