Rock Solid Fab 5.7 Hemi Comanche

[Team Willys]

The engine hoist can really get in the way when trying to fab things up, and I knew I wanted the chassis side engine mounts to bolt on just like factory. I decided I should use as many of the stock holes as possible, so I utilized both the 4 cyl and 6 cyl mount holes/studs to help spread out the load of the more powerful engine. The Hemi weighs 30 lbs LESS than the 4.0 did, so that was a negligible difference, but with almost double the HP compared to the 4.0, I saw it fit to beef the mounts up. I started with CAD (cardboard aided drafting, although I do actually use computer aided drafting for most of the parts I make lol) and made templates on how the plate needed to be cut to fit. Once I had all my templates made, I began tracing them and cutting them out of 3/16 A514 Domex steel, which is 100,000 psi tensile strength (compared to your typical A36 which is only 36,000 psi and is used by most manufacturers). I then bent them and tacked them together to give me a super rigid mounting surface for the mount tabs.

Once the frame plate were all fit up, I finish welded them and bolted them back in. I then needed to have plates for the engine side. I dre some up in AutoCAD and cut them out on the torchmate for a clean design. I bolted them on the engine, then slid it back into the truck and bolted it back up to the transmission for the second time. With everything reinstalled, I moved on to connecting the engine mount plates to the frame mount plates. I utilized a sleeve with poly bushing typical of a Jeep lower control arm. then I just had to make tabs for each side to connect everything.

 

[Ricky Rodder]

That's looking fantastic. Looking forward to seeing more

 

[Team Willys]

Once the engine mounts were finished up completely, I went ahead and reinstalled the engine again so I could move on to test fitting other things and boxing in the fire wall.

I was concerned about hood clearance from the start of this project. the Hemi is only a little taller than the 4.0 (from crank centerline) but it still was difficult to package. I needed to get the engine as high as possible so it would clear the track bar and drag link at full bump, but going too high put the bell housing into the tunnel. The clutch and flywheel are bigger on the Hemi, Magnum V8's, and 3.9 V6 than they are on the 4.0, so the bell housing is obviously bigger too. I raised it as high as I was comfortable with, leaving about 1/2" gap between the bell housing and the tunnel... then built the mounts pictured above!

I was eager to test fit hood clearance, but sorta expected to need an aftermarket hood. I installed the engine cover and slowly shut the hood. With the header panel off, it was very easy to see what was going on as the hood was lowered. To my surprise, it fit perfectly! There was about 3/4" at all places which is plenty of room.

Since the start, I wanted the finished product to look factory, so I didnt want to build a custom "cold air intake" (lol, more like hot air intake!). While scouting for parts at the local Junkyard, I found an 06 Charger with a hemi and the air box looked promising. I pulled it and the air tube out and ran over to a Cherokee... I pulled the stock airbox out of it, and test fit the Charger box. It appeared to be very promising! The fit was almost perfect. So now with the engine in the truck and the hood closing, it was time to try it out for real!

Turns out. it fit perfectly after all and the hood shut over it too! Although its close, there was no contact.

Next step was to start patching the firewall. I made templates out of poster board and then transferred those patterns over to some 18 GA sheet metal.

 

[PacificEd]

Excellent workmanship and skills as usual. It looks great!

 

[Team Willys]

Thanks Ed!

More pics will be on the way soon. I just don't have a ton of time... Currently working on a WJ brake/knuckle swap on a YJ and doing a built 6.4 Hemi in a 2013 JK...

 

[Team Willys]

Sorry for the delay in pictures, I have been absolutely swamped with work. I haven't had a full day off in over a month but there is finally light at the end of the tunnel. But trust me, there are more tunnels.

Anyway... back to the story on how to install a Hemi into an XJ or MJ.

Since the firewall was modified, it wasn't possible to retain the stock HVAC box. I wasn't too worried about that since the stock A/C system wasn't very good anyway. I had literally replaced every single component with 95 Model year stuff when the 4.0 was in it, but the R12 style condensor was very inefficient for R134a so it really was terrible.

I decided I would look into an aftermarket system from Vintage Air. I was able to find a system that would fit perfectly behind the stock dash. I went with the Gen 2 Super as it was the biggest unit that would fit. I test fit it and made a few mounts.

I cut the bottom off of the defrost duct and made some small filler panels out of 18GA sheet metal in order to adapt it to the VA defrost flex duct. I also had to make a panel for the back side of the dash to allow the vent flex hoses to be inserted into it to allow the air to flow through the dash like factory.

 

[Team Willys]

Sorry for the delay in pictures, I have been absolutely swamped with work. I haven't had a full day off in over a month but there is finally light at the end of the tunnel. But trust me, there are more tunnels.

Anyway... back to the story on how to install a Hemi into an XJ or MJ.

Since the firewall was modified, it wasn't possible to retain the stock HVAC box. I wasn't too worried about that since the stock A/C system wasn't very good anyway. I had literally replaced every single component with 95 Model year stuff when the 4.0 was in it, but the R12 style condensor was very inefficient for R134a so it really was terrible.

I decided I would look into an aftermarket system from Vintage Air. I was able to find a system that would fit perfectly behind the stock dash. I went with the Gen 2 Super as it was the biggest unit that would fit. I test fit it and made a few mounts.

I cut the bottom off of the defrost duct and made some small filler panels out of 18GA sheet metal in order to adapt it to the VA defrost flex duct. I also had to make a panel for the back side of the dash to allow the vent flex hoses to be inserted into it to allow the air to flow through the dash like factory.

 

[Team Willys]

After mounting the HVAC system it was time to move on to the cooling system. I knew even the best 4,0 Radiator probably wasnt going to cut it for the Hemi, so I ordered a 19x24 2 core all aluminum radiator from Summit Racing and trimmed the front cross member so it could drop down into place and fit under the upper header panel support.

Using a hole saw, I placed a hole in the core support to allow the radiator cap to pass through.

Then I dug through all the radiator hoses at the local parts store until I found 2 that would fit perfectly after some minor trimming.

With the Radiator done, it was time to plumb the HVAC system up. I installed the VA firewall pass through and started running the heater hoses and A/C lines.

I mounted the new 97+ condensor (basically in the stock location just moved forward a little) and ran the A/C high pressure hard line.

The low pressure (suction) line was a total pain in the rear. I wanted to use the stock WK grand cherokee line but the bend was off at the compressor and it was hitting the steering shaft. I had to completely rework, weld, bend, and modify the compressor end of the hose, and then I basically had a Vintage air fitting welded to the firewall end. I took all of them to the local custom A/C shop to have all of the hoses and lines crimped and welded as needed.

 

[Team Willys]

An often overlooked aspect of an engine swap is the fuel system. I didn't want to spend a bunch of money converting over to s return style system with billet fuel rails and braided aftermarket AN style hose and aluminum fittings. Thats over kill for this project, plus, it doesn't look stock. I also didn't want to run rubber fuel injection hose because its expensive, and also doesn't look stock. While at our local Hydraulic Supply company, I discovered that they stock the lines and OEM style plastic quick connect fittings designed specifically for fuel systems. But...the Hemi is returnless since late mopars regulate fuel pressure at the tank itself. It just so happens that the Hemi and LS engines operate at the same fuel pressure. I decided to run a Corvette fuel filter as it would add an extra layer of protection for the injectors plus it has the regulator built into it, giving me an inlet, a return line, and an outlet to engine. I mounted it to the firewall and plumbed it up using the OEM style lines from Hydraulic Supply.

I ran the lines from the stock hard lines on the frame up behind the engine to the filter on the firewall. I put them in heat protective sleeve to keep them from getting hot and melting.

Hydraulic Supply also carries the adapter fittings to convert Power Steering boxes and pumps over to a -6 JIC (same thing as a -6 AN) so I also had them whip up the pressure line for the power steering system.

I then needed to tackle the low pressure side of the steering system. The pump I used was from a Hemi Charger but they have a remote reservoir. I built a simple bracket to hold it and was able to use the OEM hoses from the Charger. It helped save money and they are pre molded so they fit very well and don't collapse.

To keep with the theme of "make it look stock" I wanted to run a stock air box but I knew the 4.0 box wouldn't fit or flow enough. I searched at the Junkyard and tried a few options by test fitting various boxes into a Cherokee. I settled on an air box that was also from a Hemi Charger... I wasn't 100% convinced it would work, but turns out with very minor trimming it was perfect. I was even able to keep the "cool air duct" functioning!

 

[XJwonders]

That’s a lot of killer work man. Keep that up.

 

[POSJ]

No update since August, makes me sad.

 

[Team Willys]

I still have more updates to do. But honestly the lack of interest wasn't very encouraging. When you aren't getting any feedback along the way, and there's a ton of actual work to be done, it makes updating your build thread fall down towards the bottom of the priority list!

One day I will sit down and give the thread an update!

 

[Anak]

I am sure there are a bunch of us who are just looking at this and saying "Wow!"

But we don't know what else to say.

It is a very impressive build, and I would love to see more of it.

Please do find the time to add more pics.

 

[Ronbo]

I am sure there are a bunch of us who are just looking at this and saying "Wow!"

But we don't know what else to say.

It is a very impressive build, and I would love to see more of it.

Please do find the time to add more pics.

X2

 

[XJwonders]

I am sure there are a bunch of us who are just looking at this and saying "Wow!"

But we don't know what else to say.

It is a very impressive build, and I would love to see more of it.

Please do find the time to add more pics.

X3

 

[Rob Mayercik]

X4.

 

[SlowXj]

When you read a build and become speechless it says something in itself... This is an insane amount of work and beautiful quality... Congrats on building the nicest Comanche by far.

Sent from my SM-G950U using Tapatalk

 

[POSJ]

Feedback!!! Dude we love the build, but since social media gives feedback within minutes most don't use websites anymore. Please give us updates.

 

[dasbulliwagen]

Please keep updating, this thing is awesome! Cant wait to see it finished!

 

[PacificEd]

I want to hear about the wiring most of all. GM seems to have it figured out on making the computer stand alone to run an engine which makes GM the most popular swaps.

On a Dakota forum I was looking for the information on how to make a 5.2 magnum with FI work in an older Dakota (1988) with a carb. There was nothing out there to explain how to do it (or if it was, I wasn't smart enough to find it).

Please let us know how your dealt with the computer and wiring.