using YJ 4.0 intake manifold on CJ 4.2

using YJ 4.0 intake manifold on CJ 4.2

seanmnew

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Colorado Springs
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86 CJ7 & 06 Liberty Sport
So I went down and talked with some guys at FN Jeep here in Colorado Springs... the guy said what he recommended was to use the intake manifold and exhaust manifold (because the way that bolt up) off of a YJ 4.0 onto my 4.2 to convert it to fuel injection. Said he has everything I need for the hardware, all i would need to find is the harness out of a 4.0 YJ and a ECU from the same... (both quick EBAY finds)... anyone have any knowledge and/or words of advice on this on? He quoted me $350 for everything i will need to do the swap minus the gaskets and header and harness and ECU... said if any of it was defective he could replace them
 
So I went down and talked with some guys at FN Jeep here in Colorado Springs... the guy said what he recommended was to use the intake manifold and exhaust manifold (because the way that bolt up) off of a YJ 4.0 onto my 4.2 to convert it to fuel injection. Said he has everything I need for the hardware, all i would need to find is the harness out of a 4.0 YJ and a ECU from the same... (both quick EBAY finds)... anyone have any knowledge and/or words of advice on this on? He quoted me $350 for everything i will need to do the swap minus the gaskets and header and harness and ECU... said if any of it was defective he could replace them


I'm confused..Did you change the head as well? I don't think the 4.0 and 4.2 heads are anything alike. The 4.2 ports are in a straight line, both exhaust and intake, and the 4.0 ports are staggered. I'm pretty sure you cant cross swap the intake or exhaust between the two.... But I sure as hell aint no authority on the matter.
 
I can hardly wait:lpopcorn:
 
A YJ 4.0 intake and exhaust will not bolt to a 258 head. The 4.0 head has higher intake ports. You can mount a 4.0 intake on a 258 head with some work and run the 258 exhaust. Why can't this guy sell you the harness and computer also? His price is WAY to high in my opinion. You can buy a YJ intake and injection system on E-bay for around $50.(I've bought them for under $20.) I swapped a 4.0 into my '83 CJ. If you stay with your 258 and use aYJ harness you'll have to use a 4.0 flywheel and starter or buy the Hesco front balancer kit($300.) With the 4.0 flywheel you have to make an adapter for the CPS and cut a hole in the belhousing. I modified my T176 bellhousing and grafted in a YJ harness(lots of hours on the internet and going through a factory service manual to get the right wire colors). On the 258 you'll also have to swap in a 4.0 distributor. You will also need a VSS from a '91 YJ or a late '80's Dakota along with a speedometer cable adapter that as I believe is no longer produced. The adapter is found under dash on some early XJ's with cruise control. Good luck with your swap. I am VERY pleased with my 4.0 MPFI swap!!
 
I did the 4.0 head conversion on my J-10. I am using the 258 intake but I am running a header.:cool:
 
Novak is doing a CPS mount for 258 bellhousings so you can run factory FI on 258's.

About the AMC / Jeep I6 Engine - Novak Conversions

Scroll down a little and give them a call. these are first rate guys.

Do the 4.0 head and manifolds and get FI in one shot. The closer you stay to factory stuff, the better off you are, IMHO

Paul
 
The bell housing mod isn't a big deal. I used a 1" holesaw to put the hole in the bellhousing and made the CPS adapter from a pattern on the internet. The info is out there just search for it.
 
I used 1/8" steel to make the CPS adapter. Those are 258 manifold washers for spacers. I was off slightly with the 1" holesaw so I used a die grinder and opend it up to where I needed it to be.
CPSbracket1.jpg
Then I cut a piece of roofing rubber for a gasket/seal. Drilled and tapped some 8-32 holes and used stainless screws to secure the seal. Ismeared some black silicone between the rubber and bellhousing.
CpsSeal.jpg
 
Looks Good! That's what Cj's are all about. Ingenuity and innovation. many Jeep folks simply throw money at their vehicles. That's not what this is all about.
 
I ended up trimming off the ends of the CPS. The end of the CPS is approx. .020 from the 4.0 flywheel. Centerline from the sensor is 2.425" from the center of the upper drivers side bellhousing bolt. This is my CJ's T176 bellhousing, I used the Hesco pilot bushing to mate the 4.0 crank with the T176 input shaft. I used the CenterForce II clutch off my 258. With the 4.0 flywheel you have to run the 4.0 starter.
CPSbracket2.jpg
 
I ended up using an airbox and tube from a '97 TJ. Rather than mount the fuel pump in the tank I mounted the NAPA P74155 fuel pump on the frame cross member. I ran new fuel line from the tank to a universal 5/16" NAPA #3002 fuel filter then stepped up to the fuel pump.Out of the fuel pump I used the 5/16" NAPA high pressure rated fuel line and steepped it up to 3/8" going into a NAPA high pressure fuel filter #FIL3486 (standard replacement for a '93 YJ) from there I connected to the CJ's steel fuel line to the engine bay. I bent some 5/16" steel line around the front of the frame to the drivers side and used the high pressure hose to connect to the 4.0's fuel line. I also used NAPA 1/4" high pressure hose for the return line, I don't think I really needed high pressure hose on the return side but better safe than sorry for the small investment. Grafting the '93 Wrangler wiring harness into the CJ engine bay was pretty simple. I used a Factory Service Manual to figure out what wires to connect.
 
I used a 1995 XJ 4.0(swapped on YJ waterpump and alternator brackets), 1993 YJ harness, '95 XJ computer(computer I originally bought had theft control-try to get an XJ buddy with theft control to let you disarm it-yeah right). Red and black wire(10 ga) from YJ harness to Red wire(10 ga) on CJ bulkhead(this is the wire that originally picked up power from the solenoid on the CJ), yellow and white wire(about 16 ga) from the YJ harness to the red(about 14 ga) on the CJ bulkhead(switched power). Yellow wire(16ga) from the YJ harness-wasn't in the harness where the FSM said it was, turned out they moved the wire, due to a salt issue,to the harness going into the firewall to the left of the master cylinder as you stand at the radiator('93 specific, was in the supplement manual I didn't buy-I wouldn't have looked if I did buy it) to the light blue wire(14 ga) on the CJ bulkhead(crank-to-start). I pulled the brown/white wire from the YJ harness where it goes to a plug for the tranny and grounded it(nuetral safety switch). I swapped the CJ oil pressure switch with the XJ one. The tach wire is grey/light blue and the MIL(check engine) wire is black/pink.
 
I used a speed sensor for a '91 Wrangler. This has the provision for the mechanical speedo and hook up for the 'puter. Good luck in finding the speedo cable adapter, Chrysler discontinued it. You have to find one off an XJ cruise control under dash module.
 

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