4.0 head and EFI on a 4.2 block

[Jeep-Power]

This is a copy of an article I wrote for the Jeep club I am a member of-- I am cutting and pasting it here. I hope it helps!



This install was done in October of 2007




First things first-- I stripped the head-- the valves, rockers, bridges, and pushrods went in the trash. All we are keeping are the bolts, spring caps, and keepers.








This being a junkyard head, it looks like some water got in-- we are having the head magnifluxed (it passed-- no cracks! ), reground the seats, and flattened. It will look brand new!





Parts List-

First-things-first: grab EVERYTHING off the donor XJ (91-95), which includes: the head, intake (w/ throttle body and injectors/fuel rail) and exhaust manifolds, computer (PCM), complete engine bay wiring harness in one piece (cut off the trunks that lead throught the fire wall), fuse box (PDC) & its' mounting bracket, throttle cable, MAF sensor (on firewall, above valve cover), distributor and ignition coil, waterneck, all the sensors (O2, water, Etc). The crank position sensor (CPS) on the bellhousing you will not be used, just unplug the harness from that sensor. All this was under $300

Aftermarket parts:

here is a list of parts and their numbers to order from HESCO

VSS-(vehice speed sensor)- PN: HES7015 ~ $122
VSS connector- PN 4414048 ~ $14.50
91-95 Adjustable Fuel Pressure Regulator- PN: HES9195FR ~ $189.00
91-03 Crank damper/sensor kit- PN: HES9199ED ~ $289.00 BE SURE TO VERIFY WEATHER IT IS FOR A V-BELT OR SERPENTINE SETUP!!!
Crank Sensor Connector- PN: 56016983 ~ $14.00

Here is some stuff to get from Summit:

Fuel pressure gauge: SUM-800160 - $17.95
Hi-flo thermostat: EMP-309 - $12.95
fuel pump block off plate: SUM-402035 - $3.95

Auto Zone Fuel Pump- PN: E2000 ~ $95.99

As said above, we chose to rebuild the head-- we had iit magnifluxed, the valve seats reground, and the head milled flat (it needed about 0.010 milled off). We are replacing the pushrods, rockers, valves and springs with new stock parts. We haven't picked it up yet-- still waiting for a call from the machine shop.

The trick to this whole install (other that the wiring 8-[ ) is that there are small casting holes in the water jacket that need to be filled in. These holes need to be filled due to the slight difference in block design between the 4.0 and 4.2. If they are not filled, the anti-freeze/coolant will literally pour out of the engine when it is filled. JB weld takes care of it. It is really easy to do and VERY reliable. Many have done it before me. The other conversion I did on my own Jeep has lasted more than 3 years an 30K miles without a drop leaking out. Stay tuned for the pics on the sealing process.


-Well, instead of working on the D300 today-- I did put a little time in on the head-


Tom dropped off the head and parts from Read Auto yesterday AM. As far as I know it cost about $700 for the parts and machine work. As I may have said above, this includes the valves, springs, rockers, pushrods, head gasket set(Valve cover, valve stem, manifold, head, water neck, etc), O2 sensor, Coolant Temp Sensor(CTS), boiling and cleaning the head, magnifluxing, regrinding valve seats (3-angle?), and milling the head flat.

Nice and clean!





all the parts-- it is amazing what a simple rebuild costs-- going with HP stuff certainly cost $$!



This is the "majic number" -- the 91-95 HO head (PN- 7120) is said to be the most desireable (according to the 'Strokers' list serve). It is located on the drivers side of the valve cover, under the fuel rail, above the #4 exhaust port.



Photo of the valve seat grind



This is how I filled the holes-- these are the water soluble packing peants-- the literally turn water milky -- so we aren't worried about them effecting the cooling system. I couldn't get my hands on some when I did my head, so I eneded up using chunks of oatmeal cookies wrapped in toilet paper. I think these work much better! I got the idea from an article I read years ago, I am sorry I cannot give that person their due credit.



Here is a detail of the filled hole, they are inserted so that there will be about a 1/4" of JB Weld in the hole. A note on this to any nay-sayers -- my drag racing neighbor(he has 3 "Wallys") tells me that he has seen JB Weld used successfully to repair O-ringed engine blocks! I have had my sealed 4.0 head for 30K miles without so much as a drop of anti-freeze leaking out.



Doin' the Deed-- it is simple work, took about 1/2 hour and half of each tube of JB Weld to fill all the holes. Uncured JB Weld cleans up easily with denatured alcohol.



Just to prove the point that these passegeways are NOT needed (they are leftover form the casting process)-- you can see here that the head gasket will seal them off in the factory application.

[Jeep-Power]

In between all the other projects, I've had a few miutes to install some valves in the head:

First thing you need is 'lapping compund'


The second tool you need is the suction cup tool --


slap a little of the lapping compund on the seating edge of the valve and then pretend you are starting a fire by rolling the suction cup tool handle between your palms, as you are rubbing them together-- I like to pick it off the seat every few turns to get some fresh abrasive in there. Here is what it looks like to me when ready. The valve on the left is the one that is 'done'.


I clean all the abrasive off the valve and seat and then apply a little assembly lube to the valve stem. Then slide it in and install the valve stem seal on the top-- alittle Vaseline on the seal first!

seals


installed seal-- it also holds the valve in the head, for the next step


next comes the new spring and its' retainer(I reused the old ones)



the valve spring comperssor-- I beefed this one up with the cross brace-- it helps ALOT with keeping the "C" from spreading


the keepers (again, reused the old ones) are installed and held in place with alittle (you guesed it!) Vaseline


Done and ready for the next one!

[Jeep-Power]

OK-- well it's been about 5 months since we touched the thing, but this past Wednesday (two days ago) Tom brought the YJ over for the "final leg" of the operation. If I haven't mentioned it before, it is an '89 YJ Laredo. The AC still works!

Tom, the owner of the YJ, here he is -- hands still clean and still smiling! Aprox 9:45 AM



What the engine looked like when he pulled it in-- Weber Carb (air cleaner was just removed)



Valve cover off


Head off





side by side-- the new head is up-side-down. I'm sorry I didn't get a pic comparing the combustion chamber differences. From what I know, the 4.0s' is significantly smaller, therefore producing an increase in the compression ratio.



New head on-- installing new pushrods and rockers




manifolds-- opps, forgot to weld on the O2 sensor bung. We'll put it on the downpipe...



new HESCO harmonic balancer/CRPS (crank position sensor)--

Top view


bottom view




Tom installed the MAP (manifold absolute pressure) sensor where one of the original emission components was mounted to the firewall.


The first injector goes in


the donor wiring harness. I forgot how much head scratching and factory service manual searching it takes to figure out what to keep and use out of this thing-- wow.


Running! -- we hot wired it up ad got it rinning that night-- at around 11PM. It started right up-- wow were we happy!!!



We had discovered that the water pump was about to give up the ghost (tons of wobble in the shaft)-- so Tom had picked up a new one to install.

We also soon found out that there was a issue with the ignition circut-- we could get the thing to crank and start, but it would not shut off-- the volt meter showed that there was 7.5 - 8 volts floating around after the key was turned off. I knew there was an easy fix and started searcing the Strokers list serve (an email list all about modifing the Jeep I-6). It was then I remembered that I had to install a diode in the field supply wire on the alternator-- pics of that to come. One the diode was installed (marked end twards the alternator), the engine shut off with hte key.

Here it is with the wiring all tucked away.



We retained a small portion of the original wiring in the PDC (power distribution center)-- the fuel pump relay and the ASD (automatic shut down) relay. As far as hot wiring it-- the big red wire on the side of the PDC needs to be hooked to the hot side of the battery ( I removed the 4 gauge monster and eplaced it with a more manageable size of 12 gauge) and the DARK blue wire that is present inthe harness gets hooked to a ignition swiched source. We tapped into the old manifold heater supply (12 ga yellow on the firewall, above the valve cover).

More detals on the wiring to come...


`

[Jeep-Power]

Tom and I were talking about the investment-- he tells me he is now in for about $2000. Still cheaper if the EFI system alone is bought new, and he is getting a rebuilt H.O. head-- where most of the power increase comes from.

I glanced through the previous posts-- I seemed to have failed to mention WHY we are doing this. So for any of you who have been wondering...

The pre- '87-'90 YJ's and '81-'86 CJ's came with carburetored 4.2 I-6s'. For whatever reason, these carburetors were 'computer controlled'. Some sort of oxymoron if you ask me. Anyway, for anyone who has had one of these setups-- you know what I mean when I say it is a DOG!!! The jungle of vacuum hoses & switches is unbeliveable. The stalling, extremely poor fuel mileage, and lack of remedy has lead many to seek out a better fuel management solution. Aftermarket carburetors and tricking the computer have brought some success. These images will bring back dark memories (and an increase in blood pressure) for many:








Well, fourtuantely for us all, in '91 Jeeps got the HO 4.0 I-6. It was soon learned that the 4.0 and 4.2 shared almost all the same dimensions. This means that both engines share ALOT of the same parts or atleast the same mounting locations/dimensions for parts. Some folks have learned to take a crank and rods from a 4.2 and install them in a 4.0 block (with 4.0 pistons) for a stroked engine-- this takes the displacement up to about 4.5l. Bore it a little (0.060) and you can get a 4.7l Torque monster.

Another benifit of the 'parts-sharing' design of the two engines it the ability to steal a head and EFI off a 4.0 and slap it all onto a 4.2 bottom end. It literally bolts right up! (I swear the Jeep engineers had this head swap in mind when they designed the 4.0 :-k ) The power, throttle response, & reliability gains are amazing. This is due in part to the larger displacement of the 4.2 and to the fact that the 4.2 pistons are shaped differently. This different shape (not as dished as the 4.0 pistons) raises the compression ratio to something like 10:1. Higher compression means more throttle response and TORQUE. It literally wakes up the wheezing 4.2. I continue to be amazed my mine.









Here are some more detail pics-- for the intention of what to expect and to plan for--

here is the diode installed on the alternator-- it prevents voltage from "leaking" back into the system after the ignition is turned off. When this leaking occurs the computer gets enough power to NOT shut off the engine! . A diode is basicly a elecrtical check valve-- power flows one way through it and not the other. I'm pretty sure it is some anchient version of a diode-- or otherwise some heavy duty version-- I dug it out of my fathers' ancient collection of electronic components-- all I know is that it works! Ideally we've wrap it in heat shrink. I did zip tie it to the heavy red wire right after this pic.



We reversed the coil on it's OEM bracket and bolted it to the block using the fuel pump mounting bolts-- the bolt pattern was exactly the same! This photo isn't the best-- I had to shove the camera underneath the heater hoses...


The exhaust--- what a PITA-- let me make it easier on you by reccomending that you order NAPA exhaust pipe part # 44626 and cut it where it straightens out to pass under the bellhousing. See where the shiny pipe ends??? Then cut the original pipe to meet up with it-- Bolt it all in place and tack weld it in place. I had this crazy thing in and out numerous times ](*,) . The cool thing with using this new section is it bolts right up to the manifold, has the O2 sensor already welded on, and has all the right bends to clear the engine and bellhousing!



Ahhhh... the speed sensor (VSS). This little ditty is crucial to optimum performance and fuel economy. The PCM needs it to know what sort of load condition the engine is under-- otherwise it's just guessing. I ran my 4.0 head conversion for more than a year before I hooked mine up. It ran pretty well and had plenty of power. Adding it increased my highway fuel mileage by more than 25%-- can get 21MPG-- 17 with the 34's. Be sure to order the VSS from HESCO-- that includes the VSS, the speedometer cable adapter (aluminum thing between cable and black plastic sensor), and the plug-- the plug is a few $$ extra, but worth it! Hook up the signal (white w/orange stripe) & the ground (black w/blue stripe).


"The Notch"-- note that the distributor tab has had one of the ears cut off-- this is very common on stroked projects or retro jobs like this. When indexing the distributor(laid out in the FSM or here(thanks Dino!!!), the ears are usually in the way-- leaving it and turning the distributor to mount up using it will leave you with less than optimal spark and fuel timing. The OEM distributor clamp was installed and the whole thing bolted down. NOTE-- I did have to reach down inside the distributor opening in the block to set the oil pump slot was in the "11:00" position!


Distributor ready for bolting down-- note that the rotor is pointing to where the #1 spark plug terminal will be on the distributor cap. Also note that the distributor wire (3 conductor black wire) is at the "3:30" position. Perrrrrfect!
Note the red/yellow wire wrapped around the rotor-- the distributor has a hole in the bottom in which a 3/16 rod can be placed into to hold the rotor/shaft in place while indexing.



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[Jeep-Power]

Here's a shot of the '91-'95 underhood fuse/relay box (Power Distribution Center [PDC]) We gutted the thing and kept only two of the OEM relays. The two that are left are the ASD (relay "E" -- the one here on the left) and Fuel Pump (relay "B" -- the one here on the right) relays. Fuses that are kept: #2 fuse ( 30A - large green one -- upper left) & the #14 fuse ( 20A - protects the ASD circut - injectors & coil). EVERYTHING else is torn out and cut away (unless you use some for them for some auxilary circuts). The three wires that need to be hooked up are: the BIG (#4) red wire on the side of the PDC-- we downsized and lengthened it (with #12 wire). It runs right to the (+) side of the battery. The ground wires (the ones that bolt to the side of the engine block-- black with a brown stripe) get bolted back to the side of the block, and the solid dark blue wires get hooked to Ignition (+) power. Hook those three up and it is ready to run!



here's a shot of the underside-- nightmarish in appearance, but all those cut wires have no power hooked up to them-- I left them long in case they are needed again.



This is a shot of all the wires used btween the PDC and the rest of the OEM harness.


HESCO adjustable fuel pressure reglator



fuel pressure gauge installed on the fuel rail Schrader valve. It is a 1/4" flare fitting on the rail, 1/8NPT on the gauge. Remove the Schrader valve core with the same tool as a tire valve stem core removal tool.



We carefully cut the OEM hard line off the OEM fuel rail fittings and installed flexable fuel line between them and the metal fuel lines that run up under the drivers side motor mount. Be sure to use hose rated for fuel injection on the delivery side. The return is low pressure and standard fuel line can be used.





the fuel pump installed ( a bit hack, but works for now).





last but not least-- this is the OEM Cherokee throttle cable-- it has to be reatined form the donor vehicle. The cool thing is that it fits perfectly on the YJ & CJ holes in the fire wall. It is a little too long onthe pedal side. The cable clamp is a quick and easy "temporary/permanent" fix. Mine's been like this for 3+ years.



The (almost--you may see a few datails that were done afterwards) finished product-- minutes before Tom drove it home the first time (40 minutes out 78w to31N) without a hitch-- =D> =D> =D>



Well, for now, that's the end of the story of Tom's YJ. He is a VERY happy Jeeper now-- no more talk of selling the Jeep and driving the Honda all the time. There's even talk of him getting out to a NJJC meeting to see things for himself!

Ultimately-- I have to say that few of the ideas and little of the information here are mine. I owe it all to the "Strokers" Yahoo! list-serve =D>. We are group of folks that are ALL about maintaing, building, and modifing AMC/Jeep I-6's. Please join us in the on-going development of such.


To all who read this-- please do not hesitate to contact me for any info. I will be more than happy to help you any way I can!


thanks for reading,

TallPeter






Special thanks to Absolute Auto in Middlesex, NJ, Tom and Ruth, Joanna, Kim & Phil Richard, my patient neighbors, Mom & Dad (just because ), Sean Ivey, Dino and the crew on Strokers, and NJJC!


`

[Shark]

fantastic write-up. thanks for sharing. great post to start things off here.

[Shark]

does the filter up by the fuel rail replace the stock location filter or is it a second line of defense?

[Jeep-Power]

As far as i know-- there is a filter in the tank, and one right before the carb. This one just worked there-- ideally, we should have utilized a Fuel Injection rated filter, but it's all we had at photo time...

[76CJ5]

What would be the difference between this mod and stroking a 4.0l. If you used the bottom-end of the 258 and the top-end of a 242 would you have close to the same thing. Just wondering weighing my options. I already have both motors so it really does not matter what parts I have to buy.

[eliv1]

the diffrence would be displacment, peter has a 4.3L engine, while stroking a 4.0L will start at the displacment of 4.5L.

this is an option to overbore the 258 block about 0.125" and fit 4.0 standard pistons, but it will leave a very thin wall and not recomended.

my opinion is go 4.0L block and stroke it to 4.5/4.6 if possible, if not then 4.7.

[Jeep-Power]

If you used the bottom-end of the 258 and the top-end of a 242 would you have close to the same thing.

That's pretty much what we did...

I went with the 4.0 head swap on mine because I had recently (10,000 miles on it) rebuilt the 258. It just so happened that it needed to be bored the 0.030 over during that rebuild.

We did the 4.0 head swap on Toms' because the bottom end of his 258 was solid and he was looking for a cheap, quick, and easy way to get more power and relaibility from his 258.

What would be the difference between this mod and stroking a 4.0l.

for me the difference between the head swap and a full 4.0 Stroker is the head swap is an easy and cheap way of getting alot more out of the 258. The stroker will cost alot more, but if I was going to rebuild the engie anyway, I'd build a stroker. I'd have done it when I rebuilt my 258, but I didn't know aything about it nor had I heard of this group, Strokers.

[cerusmc21]

Awesome post, its been very helpfully. I am doing the same swap on my 80 cj7. I am thinking i am almost done with the whole swap. One question, how much of the new wiring harness did you use. is it just the sensors for the FI and timing? what about the alternator field and the coil?
what about the distributer? can i just put the 3 wires that go to the "sync sensor" to the 3 wires going into the original distributer.

Thanks a lot for your help, and again, great post.

[Jeep-Power]

Thanks, I'm glad to hear this has helped you!

The mod continures to prove itself to be wonderful for me and my Jeep (despite what Simon says )

I recently got a chance to test it out in Moab... works great there too!




We did use the distributor wires-- they are the cam position sensor -- the engie will not run without it hooked up 9as far as I know).

Tom kept his 4.2 alternator, so we did not utilize any of that from the 4.0 harness.

Side note-- there is a way to trick the PCM into thinking that the alternator is hooked up, by mimicing the resistance of the 4.0 alternator. I seem to remember it being something around 10 Ohms. The reason for tricking the PCM into thinking that the alternator is there is that otherwise it will constantly leave the engien light on-- I am pretty sure the same is true for the A/C relay control wire. I tricked that by mimicking the resistance of a standard automotive relay (again, from what I remember, about 5 Ohms...)

If you are not concerned with using the 4.0 check engine light, then disregard the above ramblings...


ps- There was discussion of it on CJ Offroad not too long ago regarding the correct resistaces needed to trick the PCM.. I forget what eventually came of it. It is under the "4.0 swap" forum-- probabally 6 months old now. Oh, wait a minute, [edit CJOffroad is dead...]

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[eliv1]

Peter, that tread is outdated.

a 10ohm resistor will draw too much current,

the right resistor range is 1K to 10K ohm, 2Watt resistor. it will draw as much as few mili-Amps.

[Jeep-Power]

Sweet-- thanks for the correct values!