Semi- H.o. Swap

[comanche1989]

Okay, So i have a 1989 Comanche 4 liter with a 5 speed. My engine blew, so i bought a 1992 high output engine off of craigslist. It came with the whole wiring harness, but the engine came from an automatic transmission, so i don't think the harness will work. ive heard of people who had kept the original renix harness, so I'm wondering what mods i will have to do if I decide to keep my renix wiring. Ive heard that you have to delete the egr valve to do a high output swap, if anyone could give some advice i would be thankful.

[jpnjim]

If you keep the Renix controls,

the toughest part is adapting the Renix TPS to the HO throttle body.

Basically chop down the HO TPS, and make it into a spacer to mount the Renix TPS to.

 

You also have to adapt the fuel lines, and the HO head pipe needs to be used.

 

You'll also need an HO air filter tube, and an HO throttle cable.

 

EGR is deleted.

I swapped the Renix CTS & Knock sensor in, though I don't know if the CTS was really any different.

You also need to use the GM alternator from the Renix

(& mounting brackets).

 

If the engine came out of something other than an XJ/MJ, you'll need to use the XJ/MJ motor mount brackets, and the XJ/MJ 90* oil filter adapter.

Keep the actual HO adapter that threads into the filter,

since it takes a standard filter, not Metric like Renix engines

 

 

That's all I can think or at the moment.

[ftpiercecracker1]

I think for simplicity sake he should just use all Renix controls. Then it would be a purely bolt on/bolt off affair.

[jpnjim]

I think for simplicity sake he should just use all Renix controls. Then it would be a purely bolt on/bolt off affair.

You have to adapt the Renix TPS to the HO Throttle body, unless you want to use the Renix manifolds.

Then you'll have an intake port mismatch with the higher port HO head.

 

Plus the Renix TB and both manifolds are more restrictive than the HO stuff.

 

It's been done,

but you lose most of the benefit of the HO swap.

[ftpiercecracker1]

You have to adapt the Renix TPS to the HO Throttle body, unless you want to use the Renix manifolds.

Then you'll have an intake port mismatch with the higher port HO head.

 

Plus the Renix TB and both manifolds are more restrictive than the HO stuff.

 

It's been done,

but you lose most of the benefit of the HO swap.

 

 

Hence why I said, "for simplicity sake." However, i forgot about port differences and that being the case he could just swap out the heads, but then again, what was the purpose of getting the HO in the first place. :dunno:

 

If he doesnt mind the difficulties involved in a HO/Renix hybrid, I say go for it. :D

[jpnjim]

Yeah, even the easy way is hard ;)

 

also;

 

I didn't mention it since the HO donor vehicle was an automatic,

but you also need a Renix flywheel with a Renix engine.

The tooth count changed Renix to HO.

[comanche1989]

i still have my blown renix engine, i just saw this H.O. on craigslist for 150. Got it from an xj with a bent frame. so honestly i don't care about the power, i just want a running engine. :doh: so if i swapped the heads and the alternator i could get away with running a high output engine that really isnt high output? :brows: The only thing wrong with my renix is the whole bottom end is dead. The top end is fine.

[jpnjim]

The short block is exactly the same 1987-1995

(In 1996 they went to a smaller cam, & the lower end girdle)

 

Some say earlier blocks had a higher nickel content,

but that aside,

the OBD I HO & Renix are the same below the head.

 

If you are really thinking about swapping heads, you should atleast send it out for a valve job & change the main & rod bearings in the 'new' engine.

 

Honestly though,

modifying the TPS, and just using the mix of HO & Renix parts is a LOT less work.

 

And you get around 10 more HP for your trouble.

[jpnjim]

Modified TPS;

[ftpiercecracker1]

Honestly though,

modifying the TPS, and just using the mix of HO & Renix parts is a LOT less work.

 

And you get around 10 more HP for your trouble.

 

 

mmmmmm . . . I'm gonna have to interject,

 

TPS, fuel lines, and the EGR system have to be adapted/removed, not easy if you've done it before, hard if you have never don't it, even with help. On the intake some vacuum lines also have to be lengthed and/or redirected. If I had the choice between the two, i would go for the all Renix engine with the cleaned, angled, and ported head, because A. shop does all the work and B. you would probably pick up the same gains as you would from doing all the work it takes to get the Renix controls to adapt to the HO equipment.

 

As a side note, I don't fully understand what you said about flywheels? Why is tooth count so important? CPS?

[BIGHEEP]

Okay, So i have a 1989 Comanche 4 liter with a 5 speed. My engine blew, so i bought a 1992 high output engine off of craigslist. It came with the whole wiring harness, but the engine came from an automatic transmission, so i don't think the harness will work. ive heard of people who had kept the original renix harness, so I'm wondering what mods i will have to do if I decide to keep my renix wiring. Ive heard that you have to delete the egr valve to do a high output swap, if anyone could give some advice i would be thankful.

Did the harness come with the PDC and the ECU? If so why not just swap it all over to the H.O. engine and harness? The wiring is not hard if you get the FSM for your vehicle and the doner. The wiring diagrams can be found online as well. It is just a matter if weeding out both harnesses and only keeping the wires you need.

 

BTW... You can use an auto harness in a standard.

[ftpiercecracker1]

Did the harness come with the PDC and the ECU? If so why not just swap it all over to the H.O. engine and harness? The wiring is not hard if you get the FSM for your vehicle and the doner. The wiring diagrams can be found online as well. It is just a matter if weeding out both harnesses and only keeping the wires you need.

 

BTW... You can use an auto harness in a standard.

 

 

 

I'm pretty sure you can't do that without swapping the under dash harness as well.

[jpnjim]

 

 

 

mmmmmm . . . I'm gonna have to interject,

 

TPS, fuel lines, and the EGR system have to be adapted/removed, not easy if you've done it before, hard if you have never don't it, even with help. On the intake some vacuum lines also have to be lengthed and/or redirected. If I had the choice between the two, i would go for the all Renix engine with the cleaned, angled, and ported head, because A. shop does all the work and B. you would probably pick up the same gains as you would from doing all the work it takes to get the Renix controls to adapt to the HO equipment.

 

As a side note, I don't fully understand what you said about flywheels? Why is tooth count so important? CPS?

Yes

Tooth count is different.

CPS won't trigger correctly with the wrong flywheel.

= won't run

 

 

Which is easier depends on a lot of things.

 

A professional shop probably wouldn't touch a hybrid HO/Renix swap.

Figuring it out, adapting & making the *wrong* parts work = time AND money AND has the risk of turning into a job that keeps coming back.

Also future parts interchangability is a big problem down the road when things wear out.

For a shop, 'by the book' is the best way.

I get that.

 

 

But doing the fuel lines wasn't tough,

the vacuum lines were a cake walk too.

The EGR goes away with the manifolds,

throw the relay away and its over.

 

 

You do have to get, and adapt an HO head pipe to the exhaust to have a spot for the O2 sensor.

 

The newest Renix is 22 years old,

so HO into Renix swap is pretty common now,

with builds on line to follow,

so its really not that difficult.

 

Either way works,

but if I was going to rebuild the bottom end,

I'd slip a stroker crank in there ;)

[jpnjim]

Also,

I don't think I ever took pics to compare them,

but there is a big difference between the HO & Renix head

 

Renix basically cleaned up the 258 head (intake & exhaust)

then added little half circles at the top of the intake ports for some room to locate & aim the injectors.

 

Chrysler came along and raised the entire intake port, squared off the top, and greatly improved the flow.

They also made the intake manifold bigger, the throttle body bigger, and turned the Renix's so-so tubular exhaust into a decent flowing, shorty header.

 

It did give up some bottom end torque,

and as a proud AMC guy I would always point that out,

but side by side its easy to see how superior the later stuff really is.

 

You could always build a throttle body adapter to keep the renix TB & TPS intact,

but that TB is a choke point even with the Renix head

[BIGHEEP]

I'm pretty sure you can't do that without swapping the under dash harness as well.

Nope, you can use the same under dash harness. You just have to repin the blukhead connector to match the MJ. I swapped a 93 XJ 4.0L into my 1988 YJ with a carbed 4.2L and I used the same under dash harness. You can actually swap in the new engine, hook up the fuel and get it to run by just splicing in 5 wires.

[jpnjim]

 

Nope, you can use the same under dash harness. You just have to repin the blukhead connector to match the MJ. I swapped a 93 XJ 4.0L into my 1988 YJ with a carbed 4.2L and I used the same under dash harness. You can actually swap in the new engine, hook up the fuel and get it to run by just splicing in 5 wires.

 

Where were you when I did my HO to Renix swap? ;)

 

Did you use the speedo sensor for the HO?

Isn't there a 1 year only speed sensor that also retains the cable drive speedometer? (1991?)

[BIGHEEP]

Where were you when I did my HO to Renix swap? ;)

 

Did you use the speedo sensor for the HO?

Isn't there a 1 year only speed sensor that also retains the cable drive speedometer? (1991?)

Actually I didn't ever get around to hooking up the speedo. I just put the XJ VSS in the t case just to get it running and never got around to swapping it back out. I have been using a GPS as my speedometer.

 

As for the VSS that will hook to a cable speedo, you are correct. You need a 1991 YJ VSS. I actually bought one and have yet to install it. It is pricey too, about $70.

[ftpiercecracker1]

Yes

Tooth count is different.

CPS won't trigger correctly with the wrong flywheel.

= won't run

 

 

Which is easier depends on a lot of things.

 

A professional shop probably wouldn't touch a hybrid HO/Renix swap.

Figuring it out, adapting & making the *wrong* parts work = time AND money "AND has the risk of turning into a job that keeps coming back.

Also future parts interchangability is a big problem down the road when things wear out." (this was my biggest grievance)

For a shop, 'by the book' is the best way.

I get that.

 

 

But doing the fuel lines wasn't tough,

the vacuum lines were a cake walk too.

The EGR goes away with the manifolds,

throw the relay away and its over. Relay? :hmm:

 

 

You do have to get, and adapt an HO head pipe to the exhaust to have a spot for the O2 sensor.

 

The newest Renix is 22 years old,

so HO into Renix swap is pretty common now,

with builds on line to follow,

so its really not that difficult.

 

Either way works,

but if I was going to rebuild the bottom end,

I'd slip a stroker crank in there ;)

 

 

 

 

Well said. :thumbsup:

 

and that last bit about the stroker? If only its was that easy. :(

[ftpiercecracker1]

Nope, you can use the same under dash harness. You just have to repin the blukhead connector to match the MJ. I swapped a 93 XJ 4.0L into my 1988 YJ with a carbed 4.2L and I used the same under dash harness. You can actually swap in the new engine, hook up the fuel and get it to run by just splicing in 5 wires.

 

 

 

Thats nice to know, but how would you know how to repin the connector? That would be a pretty sweet writeup, :brows:

[jpnjim]

 

 

 

 

 

Well said. :thumbsup:

 

and that last bit about the stroker? If only its was that easy. :(

 

Yeah,

I just finally clicked on your thread.

 

That sucks getting the run around

 

Hope you get it up & running soon.

[jpnjim]

 

Actually I didn't ever get around to hooking up the speedo. I just put the XJ VSS in the t case just to get it running and never got around to swapping it back out. I have been using a GPS as my speedometer.

 

As for the VSS that will hook to a cable speedo, you are correct. You need a 1991 YJ VSS. I actually bought one and have yet to install it. It is pricey too, about $70.

 

I have a YJ/HO harnesses & computer somewhere,

if I ever get around to swapping the later horseshoe intake on,

maybe I'll use that as an excuse to do the full HO swap at the same time.

 

Atleast I know who to ask if I get in over my head :)

[BIGHEEP]

I have a YJ/HO harnesses & computer somewhere,

if I ever get around to swapping the later horseshoe intake on,

maybe I'll use that as an excuse to do the full HO swap at the same time.

 

Atleast I know who to ask if I get in over my head :)

Anytime.

[comanche1989]

So to swap in the H.O. with the renix wiring, I would have to modify the tps, get a high output intake tube , the egr would delete, then i would have to get an H.O. downpipe for the o2 sensor. Id swap the alternator, then I would be set, right? Any other big mods needed to get the H.O. running on the renix harness? the injectors would hook up just fine to the harness, correct?

[jpnjim]

 

Anytime.

 

thank you! :)

 

So to swap in the H.O. with the renix wiring, I would have to modify the tps, get a high output intake tube , the egr would delete, then i would have to get an H.O. downpipe for the o2 sensor. Id swap the alternator, then I would be set, right? Any other big mods needed to get the H.O. running on the renix harness? the injectors would hook up just fine to the harness, correct?

 

Standing over my own bastardized hybrid ;) ...

 

Yup, renix electrical harness on HO injectors -check

Swapped alternator AND mounting brackets -check

+ vacuum hoses (really not many left if you ditch the airbox)

+minor bolt ins of the coolant temp sensor @ rear of head

(I left the unused HO sensor in the thermostat housing)

&knock sensor just above the oil pan.

 

Biggest thing after all the above + what you mentioned is the fuel lines.

 

You have to use the HO fuel rail, so you have to shorten one, or both of the MJ's fuel lines to work with the lines on the HO rail (I forget if I had to shorten 1 or both)

^ IIRC, I made new ends for the quick release connectors with a flare tool & some practice

 

If you were swapping in a 96+ engine you'd have to get a 91-95 fuel rail (96+ = no return line)

 

If you have a YJ/ TJ/ZJ engine you'll need to swap the smaller XJ/MJ fan drive on + motor mount brackets & possibly the 90* oil filter adapter.

 

And Heater hoses,

Most people upgrade to the HO's cooling system too,

& eliminate the renix's heater-hose tangle of snakes.

IIRC, for me this meant I deleted a valve that routes coolant away from the heater core when its not needed there.

There is a heater hose diverter valve available for HO's, I just didn't have one,

and never got one.

 

I'm a little foggy on this since the swap was 6 years ago, or so.

 

You should be able to retain the renix closed cooling system if desired,

but its not the greatest thing ever.

(Ho cooling system requires heater hoses, radiator, and a place to mount the new overflow bottle).

 

 

 

Hopefully someone else will jump in here in case I missed anything.

 

Good luck!

[comanche1989]

Thank you so much for your help! I'm hoping to get this project on the road by christmas, so i have a good amount of work ahead of me!I'll probably retain my original cooling system, mostly because I'm working on a High School budget. I can't wait to get my manche back on the road! :MJ 1: