Just found out my 89 MJ has a 91 block/head

[Airborne Janitor]

As the title states, just found out the 4.0L in my 89 MJ was built in 91 and has a 7120 head on it. However, it has all the Renix era intake/exhaust manifolds, valve cover, throttle body, ignition, wiring, etc. The emissions were gutted from this truck, it had an EGR delete plate and vacuum lines removed or capped off.

 

So of course assuming I had an 89 I have been gathering parts for an 89, including plans to reinstall the vacuum harness and EGR and an ATP exhaust manifold. Does a Renix intake/exhaust manifold mate up the an HO head properly? I checked the Renix gasket and everything lines up as far as I can tell.

 

Considering my situation, what advice would you give me going forward? My goal is to keep the motor mostly stock and set up how it was from the factory, with the exception of 746 injectors. Should I just put the Renix manifolds back on and call it a day, or am I better off swapping over HO components. I already have purchased a ton of parts and I don't want to buy new stuff, but I want this done RIGHT. Thanks.

[DirtyComanche]

The Renix intake fits the HO head better than the HO intake fits the Renix head...  Neither is optimal.  The Renix exhaust header fits the HO head fine, or it should, as you can get a stock HO header to fit on a Renix head with no issues.  The exhaust ports are in the same location.

 

I'd get the later HO intake and adapt the Renix controls to it.  Should be good for a few ponies, between giving you a large throttle body and better flowing intake manifold.

[omega_rugal]

why re add the EGR? pass emissions?

[Airborne Janitor]

why re add the EGR? pass emissions?

 

Might seem stupid to some but I'm basically doing a factory reset on this motor and want to get it back to stock as possible for the mean time. I figure AMC engineers put that rats nest of vacuum cables in for a reason. Also everything is currently capped off in ghetto-fab fashion and my policy is to do it right the first time and not have to worry about it again.

[DirtyComanche]

The EGR is of little use, IMHO, and was not included on later models...  There isn't much running it anyways, just a line from the manifold to the solenoid, and a line from the solenoid to the valve.  Either way it's junk under the hood.  Yes, my MJ still has it, but it's long gone on my XJ (which is running a HO intake and exhaust).

 

The intake air preheater setup is also of little use.  I live in a rather cold climate, and I turfed it on both my MJ and XJ.  No noticeable difference in cold starts.  That's what another one of those lines is for.

[cruiser54]

Just use the intake/exhaust gasket for the intake manifold you have. If you wanna get fancy, port match both intake manifold and head ports to the gasket.