1985 Jeep CJ-7 with a Carbureted 4.0L Inline Six

[rcomm3]

Ok, here is my situation.  i am new to the the jeep owners world.  I have wanted a cj since I was 13 yrs old and I finally got one about 2 months ago.  I bought an 85 cj7, it has a 2.5 l 4 cyl with a t4 transmission.  I bought it with the expectation of putting in a different motor and trans, however,  what I did not count on was how much body work I would end up having to do.  The body work has taken a huge chunk out of my budget for the motor.  A buddy of mine gave me a 4.0 out of his 88 comanche.  the engine ran but had been sitting for 7 yrs and all of the seals leaked, including the main seal.  My original plan was to use this motor and carburate it since I don't have all of the parts for the fuel injection and I want to keep it as simple under the hood as possible.  My question is, would this be possible and could i use the existing motor mounts. Also, what else would I have to do to make this work?  Any help on this would be greatly appreciated. Thanks

[60Bubba]

There are definitely people that run 4.0 with carburetors. I know a few folks on another forum have done it.  My CJ has a 4.0 with the MOPAR fuel injection kit.  It started life as a carb'd 258, then got the EFI kit.  When the original 258 blew up, they just put a junkyard 4.0 in it and reused the MOPAR EFI kit, as it was built using 4.0L parts to begin with.  Weird, but it works pretty much like a standard 4.0HO EFI engine.

I understand your money situation.  My project seemed to grow at every turn.  I personally wouldn't want the hassle of a carburetor swap on a 4.0, and I've read some argue the engines were built around EFI.  I'm not sure I buy that idea, as the 4.0 is nothing more than an evolution of the original 258 anyway.

I've never dealt with a 4 cylinder CJ, so I can't comment on the motor mounts.  I would bet there might be some clutch issues as well.  If I remember correctly, I think the 4 cyl was a hydraulic clutch, but the 6 cyl wasn't.  I could be wrong on that.

I would venture to bet someone will jump on here and give you some better info on the swap you are contemplating. 

[Moses Ludel]

rcomm3...The '88 4.0L engine has a different port height on the cylinder head.  This is likely not a match for the 4.2L head nor is it the same as the 1991-up 4.0L.  All U.S. 4.0L engines from 1987-90 were Renix EFI (not Mopar like the 1991-up 4.0L or the Mopar EFI conversion that 60Bubba describes).  For carburetion, you need to determine what intake manifold would be required.  Take a look at the aftermarket carburetor manifolds available from Clifford and Edelbrock.  See if they fit the 1987-90 4.0L engine.

On the motor mounts, you will need to change the mounts to Jeep inline six-cylinder type.  On your 1985 CJ, this is simpler, unlike the 1987-up frames.  AMC/Jeep used bolt-on side motor mounts on the late CJs plus a cross brace that also bolts in place between the frame rails.  You need to find a donor 6-cylinder 4.2L model and get the engine mounts and any braces that differ from your 4-cylinder application.  There were factory bolt-on side mounts used on the 4-, 6- and V-8 (1980-81) applications.  All CJ frames were the same.

The bellhousing is also different on the sixes.  You will need the 6-cylinder inline or V-8 type bellhousing.  Your 4-cylinder housing is similar to the 2.8L V-6 pattern used by AMC when they borrowed the Chevrolet 2.8L V-6 for use in 1984-86 XJ Cherokees.  (This four-cylinder AMC 2.5L bellhousing helped make engine installations easier at the factory.)  That said, you need to find a 4.2L bellhousing and the spacer "shim" (fits between housing and engine block) if you run carburetion.  You'd need the 4.0L bellhousing plus the spacer shim if you use factory EFI and need the crankshaft position sensor at the back of the engine.  

Note: I'm guessing that 60Bubba's Mopar EFI Conversion is using the conversion kit's bolt-on crankshaft position sensor at the crankshaft pulley?  We haven't discussed that item.

You'll also need an upgrade on the radiator to a 6-cylinder type and will use the fan shroud from a 6-cylinder model as well.  Beyond this and exhaust system parts, you should be on your way to an inline six conversion.  The best approach is to have a complete donor vehicle as a model prototype:  Note each of the differences between the six- and four-cylinder installations...This is much easier on a CJ than the early YJ. 

For those who would like to see what it takes to install a Jeep 4.2L or 4.0L inline six in a 1987-up YJ or TJ Wrangler originally equipped with a 2.5L four, see my article at:  http://www.4wdmechanix.com/MIG-Welding?r=1.

Moses

   

[rcomm3]

Thanks, yes the clutch is hydraulic i did not think that would be an issue as i was going to try to find an ax15 to drop in there.  Im just really torn, i want to keep it simple but i also want to make sure it is reliable.  I have a bunch of people telling me to just put a chevy 350 in and skip the six.  Thats gonna be a whole lotta money though and then im definitely gonna have to upgrade the tranny. 

[rcomm3]

Thank you Mr Ludel, by the way the first book I bought when I bought the jeep was your rebuild manual.  It is outstanding information.

[Moses Ludel]

Thanks for the feedback on the Jeep Rebuilder's Manual, rcomm3!  If you do an AX15 transmission and 4.0L, you will need an AX15 bellhousing (plus shim) as well.  You will also need to clock the Dana 300 transfer case with an adapter from Advance Adapters.  The AX15 output for the NP231 has a different bolt hole orientation than the Dana 300.

Actually, the V-8 idea is not bad if you can meet your emissions requirements.  By the time you secure each of the inline six parts plus the transmission, you might be looking at a cost similar to the V-8.  The V-8 conversion, however, does require fabrication work.  Again, Advance Adapters will be your treasure trove of information for making a decision.

The V-8 conversions are getting easier, the G.M. small-block V-8 (1986-up to get the one-piece rear main seal would be advisable) fits nicely once you work through all of the conversion chores.  Lately, the 5.3L LS engine has become popular, this involves a wiring harness and high pressure fuel system work.  For emissions, California requires a complete donor vehicle exhaust system.  Here is one swap done on a later TJ Wrangler at Advance Adapters:  http://www.4wdmechanix.com/HD-Video-Advance-Adapters-Jeep-TJ-Wrangler-LS-V-8-Conversion?r=1.

Ultimately, it comes down to personal preferences.  There's even the AMC/Jeep 360 V-8 conversion, these "classic" engines are carbureted right to the 1991 Grand Wagoneers.  That would involve more "factory" parts, and 360 or 401 AMC V-8s have been powerhouses in CJ-Jeep 4x4s.

We can bat this around more...All food for thought.  Do some price shopping on donor engines and transmissions.

Moses

[rcomm3]

Ok, well it has been a while since I last posted anything, but i have made some progress.  Well, i stayed with the 4.0 which has kind of limited me to the Clifford Research intake which as a whole kit including carb, headers, fuel regulator, and gaskets is going to run me about $1300 which is about what the engine rebuild cost.  Turns out getting a free motor is about like getting a free puppy. Unfortunately the head was cracked, otherwise the rebuild would have been $1100.  But I also found an ax15 for about $400, unfortunately THAT is a 92 with the internal slave.  I already have a new slave so I don.t have to replace it anytime soon.  I plan on trying to use the master cylinder from the t4.  I bought the mountain offroad bombproof motor mount, now i have to get the engine brackets for the 258 so i can use them.  Apparently you cant use the brackets that came on the 4.0.   

My question is, does the renix motor take a pilot bearing or bushing? I have tried to look it up but have been unable to find anything definitive.

As far as emissions go, I am in an area of southern Arizona where they have no emissions requirements.  That being said, I dont want to gas myself or anyone else out but I also dont want to deal with the vacuum tube nightmare that was on the 4 cyl. I did get the bell housing with the tr*nny and went to Novak for the transfer case adapter and transmission mount.  I was also planning to go with the DUI distributer with the ignition and coil all in one.  What is the going opinion on those? I know the dui dists. have a good rputation but I was wondering if anyone has experience in 5his application.   Thanks for any info.

Edited February 1, 2016 by rcomm3
Additions

[rcomm3]

Oh yeah, found some cracks on my frame sssoooooooooooo i had tofind a welder and learn to weld.  So far so good, the frame is patched up and new rear crossmember welded on.  I actually got the welder for free from a friend who picked up a nicer one.  It is a lincoln 135.  not the biggest but it is a really nice mig w8th thre 75/25 mix gas bottle.  I think I might be hooked.

[Moses Ludel]

rcomm3...DUI makes a quality HEI type distributor that can be re-curved if necessary.  MSC makes an AMC inline six distributor, though that may require the MSD AL box as a package.  (Research this at the MSD site to see if the distributor can be used "standalone".)  There's also an inexpensive HEI knock-off distributor sold by 4WD Hardware and others.  That's an off-shore product and perhaps forum members can comment on its reliability.

If the engine is relatively stock, an original 4.2L Motorcraft distributor and Ford-type module work; you had a 2.5L, so I'm unclear what module type your '85 CJ had originally.  (As early as my Jeep Owner's Bible, I describe easily converting to a common 5-pin Mopar style module if your Jeep 2.5L ignition wiring will not interface.)  The Motorcraft distributor curve is adequate and responsive if you run a direct (non-emission as you describe) ported vacuum hose to the vacuum canister.  We can discuss ported versus manifold vacuum if you need that info.  The DUI distributor or an aftermarket "HEI" prototype distributor would be standalone and easy to wire.  See the 4WD Hardware and other catalogs.

As for the 1987-90 Renix 4.0L engine pilot bearing, the OE part number for the crankshaft pilot bearing is  33004041 (BEARING, Pilot Manual Transmission).  This lists for both the 4.0L Renix and Mopar MPI 4.0L engines from 1988-93.  (Presumably, it would also fit the 1987 XJ Cherokee 4.0L Renix engine as well.)  This should be a needle roller bearing type and not a bushing.  The part number is common and covers quite a few model years of the 4.0L inline six with manual transmission (through the hydraulic clutch release bearing era).

Welding is a very useful skill!  Glad you're in a welding mode, practice makes a difference, stay with it!

Moses

[rcomm3]

Thanks for the info, I bought something that I thought was the right part but the diameter was wwwaaaaayyyyyy off.  So thanks for the part number, I wont go wrong with that.  This is going to sound like a really dumb question, but I was looking at my amc 20 rear today and realized that there is no fill plug on the cover.  How in the smell do you put any fluid in it after draining it?  like I said, im definitly NOT an expert in this.

 

[Moses Ludel]

rcomm3...You're welcome...For checking or filling the AMC 20 rear axle with lube, look to the side at the front of the iron center section.   The center section casting has a fill plug (tapered pipe thread type).  Post a quick cell phone pic of the fill plug to help others find the plug...

Check the gear oil with the vehicle at normal curb height on flat ground or with the axles supported and level.  Filling to the lower level of the fill plug's threads is plenty.  

If the Jeep is lifted with a CV rear driveline and pinion rotation upward, the plug will be raised, and the oil level rises.  The factory recommended refill amount, after removing the cover and draining the lube completely, may not be adequate.  Many 4x4s with a pinion rotation run with gear lube adjusted to the raised plug opening .  As long as this does not create a seal or venting/overflow issue, that's fine.  The main concern is adequate lube to the front and rear pinion bearings and the differential carrier bearings.

Let us know how this works!

Moses

[rcomm3]

So I got a set of 258 engine brackets so I can use the engine mounts I bought, however the 258 brackets dont line up with the original engine bracket holes.  If I move the 258 brackets back a little, then they will work but I would have to use a bolt where the knock sensor would have gone.  Is this going to work? Otherwise I am (oing to have to return the frame mounts I bought.  I guess my issue is that I just dont know enough to know what will work and what wont and will be disastrousif I go forward with it.

[rcomm3]

So I have been frantically searching for replacement frame tabs for a yj because those might actually work with my engines br*ckets.  Im kind of at a loss here, very frustrated.  does anyone know of any solutions here?

Ok,  figured out the photo issue. Mount issue next.  these are the original engine side motor mounts.  There are two holes to the rear of the motor mounts that line up with the 258 engine brackets but one of those holes is the hole for the knock sensor on the drivers side.

 

 

 

Edited February 4, 2016 by rcomm3
adding images and text

[Moses Ludel]

rcomm3...I have provided a PDF with details on the 1981-86 Jeep CJ motor mounts.  You will see the major difference between the YJ Wrangler 4.2L and newer YJ and XJ 4.0L engine mounting versus your traditional CJ mounting.  Note that the PDF contains info on all Jeep CJ engine mounting types (4-2.5L, 6-4.2L and V-8 304).  Look at the legend to determine the 4.2L inline six mounting system and parts: 1981-86 Jeep CJ Engine Mounting.pdf.  This will apply to your 4.0L engine.  PDF is great, you can zoom-in for sharp details.

The CJ system is actually more practical than the YJ Wrangler.  The YJ Wrangler uses welded frame brackets that pick up the top-down mount common from 1987-up.  Your mounts are angled.  The CJ engine frame brackets are bolt-on, and they differ between the 4.2L and 2.5L engines.  (See details and part numbers, they are different for the 2.5L four and 4.2L sixes.)  The problem you are experiencing sounds like the 2.5L frame brackets.  You need 4.2L frame brackets that line up with the 4.2L engine brackets (1981-86 CJ style).  

Fortunately, Jeep CJs from this era all use the same chassis/frame.  The engine frame mounting brackets for the different engine types fit at different locations on the frame rails.  This is necessary because the 4.2L engine block is longer than the 2.5L.  Note that the frame should have alignment holes for different engine types and engine frame brackets.

We can discuss this further.  I performed a 4.2L conversion into a 2.5L chassis like yours in the Jeep CJ Rebuilder's Manual: 1972-86.  (Bentley Publishers, this book is available from a variety of sources and would be very helpful for your '85 CJ work.)  I have also done a 4.0L into a 2.5L YJ Wrangler chassis that involved frame bracket welding, since the YJ uses a different chassis/frame for four- and six-cylinder inline engines.  So does the TJ.  Here's an article on that changeover:  http://www.4wdmechanix.com/MIG-Welding?r=1.

Once you get the correct 4.2L inline six pieces for a CJ chassis, this should make sense.  You'll be glad you have a Jeep CJ-7 and not a YJ or TJ Wrangler. 

Moses

1981-86 Jeep CJ Engine Mounting.pdf

Edited February 4, 2016 by Moses Ludel

[rcomm3]

Moses,

I have the 4.2 engine brackets as well as the originals.  I guess my question is, if I use the 4.2 brackets then I will have to move them back a little to fit the holes in the block.  Consequently, one of the holes I will need to use is the hole for the knock sensor.  This is located to the rear of the ds motor mount.  I also have the frame side mounts for the 4.2 which I agree will be much easier but the whole knock sensor thing has got me questioning whether I should go that route.  The PDF definitly will help if I go the 4.2 route but this motor seems to be a bit of an oddity because of the collaberation of the 2 companies that built it.  

Thanks

[Moses Ludel]

rcomm3...So if I understand, you're good to go except that one of the threaded holes for the 4.2L (CJ style) engine bracket lines up with a hole in the 4.0L block drilled to accept a knock sensor.  Right?

If so, you can do one of two things:  1) drill out the bolt hole in the engine bracket to accept a bolt the same thread size as the knock sensor threads or 2) find or create a thread "reducer bushing" (of higher grade tensile strength) to take the knock sensor thread down to the size of an engine mounting bracket hole.  It may be easier to find a correct graded bolt with the knock sensor thread size and drill out this one engine mounting bracket bolt hole to match the larger bolt's shank diameter.

Does that make sense?  Is your problem the drilled hole for the knock sensor?  Does this hole otherwise align with the engine bracket?

What is the thread size for the knock sensor?  Is this a straight thread that can be easily matched or a tapered pipe thread?  Clarify whether the thread is U.S. or metric and its pitch.  If you have the knock sensor, use its thread size as a reference.  Find a bolt of the correct design, shank diameter, thread pitch, length and tensile strength.  Make sure the bolt does not bottom in the block hole.  Measure the block hole's thread depth before buying a bolt.

Let me know if this helps.  It's not surprising that AMC/Jeep or Chrysler would take an existing casting boss on the engine block and machine it to accept a knock sensor.  What year is the engine?  Is this a 1987-90 Renix 4.0L from a Jeep XJ Cherokee?

If useful, post a picture of the knock sensor.  It looks like the 3rd block bolt hole (the knock sensor threaded hole to the rear) aligns with the bracket's hole.  Correct?

Moses 

Edited February 4, 2016 by Moses Ludel

[rcomm3]

Moses,

That is exactly the issue.  I was going to find a bolt with the same diameter as the hole already drilled which, I believe is a SAE with a fine thread.  This would allow me to use the 4.2 brackets and just slide them back a little on the motor.  I do not have the knock sensor as it was gone before I got the motor.  The engine is out of an 88 jeep commanche MJ.  If I need the knock sensor then what you ar saying is that I can drill and tap one of the other unused holes in the block to accept the sensor, right?  I am almost to the point of just selling this motor that I just had rebuilt and finding a rebuilt 4.2.  Just totally exasperated.  Thank You very much for your help with this, I know I'm being a pain but I am trying to play catch up with all of the tech knowledge.  The engine bracket bolts are a 3/8 coarse thread and the sensor hole is a larger diameter with a fine thread pattern.

Rick

Edited February 4, 2016 by rcomm3
additional info

[Moses Ludel]

rcomm3...Re-sizing just that one bolt hole on the bracket should do.  If the oversize bolt's head is too close to the bracket casting, consider using an Allen head (socket head) cap screw, they're available in Grade 8, with a matching split ring lock washer designed for an Allen (socket head) cap screw.  SAE (fine) thread should not be an issue, these socket head screws are often SAE thread.  You may need to seek out a fastener warehouse or check out http://www.mscdirect.com.  They have a large industrial supply catalog that includes this kind of hardware.   

If you can get all three bracket holes to align with the block's threaded holes by just re-sizing the one bracket hole, that would be optimal.  All three bracket holes would then be the size of their bolts, and the bracket would be firmly and securely attached!  

Note:  It is very doubtful that AMC re-positioned these block holes and made them align differently than on a 4.2L block.  The Renix 4.0L engines were built alongside the 4.2L engines from 1987-90.  Block castings and thread bosses should be very similar although the bore is larger on the 4.0L than the 4.2L.  (Despite the bigger bore, the 4.0L's stroke is shorter, that is why the 4.0L is only 242 CI while the 4.2L is 258 CI.)  If you position the frame brackets in the correct frame holes, the mounts should align properly.  Look closely at the frame, there is a different set of frame holes for the inline six brackets than for the four-cylinder's frame brackets.  Find a 4.2L CJ to compare if necessary.  Make sure you're using Jeep CJ 4.2L frame brackets in addition to the Jeep CJ 4.2L engine brackets.

As for the knock sensor, that's not a necessity since you are running a carburetor and a conventional ignition distributor.  Make sure your intake and exhaust ports on the head match the manifold gasket(s) and manifolds.  The '87-'90 4.0L engine has a different cylinder head port height than the later 4.0L engines.  This will not be a problem as long as the intake and exhaust manifolds seal properly and the gaskets and gasket cut-out holes align correctly.  Match carefully.

If you cannot get a port match, there are "universal" aftermarket manifolds and gaskets available from Clifford and other header manufacturers.   Discuss with them that you're running a Renix era 4.0L cylinder head with a carburetor manifold.  Is that manifold aftermarket or a stock 4.2L manifold?  2-barrel type?  What carburetor do you plan to use?

Moses

Edited February 5, 2016 by Moses Ludel

[rcomm3]

I am actually planning on using the Clifford Research  intake and header kit. The kit includes the intake, dual exaust header(which I will y down to one), weber 2 bbl carb and reline fuel regulator with all of the gaskets needed.  It is their 6-8 4.0 series. They are the only company that I could find that made the carb intake for that motor.  Thanks for your help with this, I really appreciate it.

[Moses Ludel]

Gotcha, rcomm3!  Makes sense, I thought you'd be headed in Clifford's direction.  Good products, the Weber should work well as a package, many go this route.  You're on the way to getting that Jeep CJ-7 going!

Keep us posted on the engine mounts and the hardware you use.  You had to work through the ins-and-outs of the 4.2L/CJ versus 4.0L MJ Renix engines, the transmission is next.  Your Dana 300 in good condition is a highly desirable transfer case.  Engine fan, crank pulley, radiator, you'll work this out.  You will need the bigger 4.2L 6-cylinder radiator for this 4.0L engine.  The 4-cylinder radiator is small unless an A/C model.  You'll need more flow rate.  The 2.5L front engine parts and accessories should fit the 4.0L, that's a plus.

You should be happy before this is through!

Moses

 

[rcomm3]

I hope you are right.  I bit off a whole lot with this. I thought id lay out my plan for the rest of the build.

Clifford intake kit

DUI distributor

aluminum 3 row core radiator (going with the mechanical fan. It gets pretty hot here).

painless wiring harness

Im going to run the 4.0 serpentine belt system so I will get the idler pullys and the ac compressor all set up since i have everythig except the pully for the ps pump.

I have already gotten the ax 15 transmission and the novak kit to attach it to my dana 300.  I also got the novak transmission mount.

After I get the drivetrain done I have to get going on the body work which is going to be substantial.  I need to replace the ds body mount as well as both floorpans, the riser and one inner wheel well.  I plan on doing the interior with bed liner and prior to that chassis saver.

 

[Moses Ludel]

rcomm3...Should be a great CJ when done...There are several here at the forums!  Make sure your water pump impeller is for a serpentine belt drive (correct rotation)...

Moses

Edited February 7, 2016 by Moses Ludel

[rcomm3]

Well, the motor is in and id post a pic but for some reason my tablet wont let me upload pics to the site.  I do have a question.  Will the DUI HEI distributer for the 232/258 work with the 242 as well? I thought it would but I am having some doubts even though I have found nothing to the contrary.  as soon as the pilot bearing and transmission parts come in, I will be assembling the trans and motor.  Cant wait, it is the hardest part of the whole build.  Waiting for parts and being able to order them.

[Moses Ludel]

Hi, rcomm3...Sounds like you're making headway!  The DUI or any other distributor should fit the 4.0L block with only one concern.  Is there a locating pin on the machined block base where the distributor housing fits?  You need a smooth surface to rotate the HEI distributor housing when setting the base spark timing.  Does the Renix EFI 4.0L block use a spring roll pin to locate the distributor housing position?

For clarification, here's an example of a common and inexpensive aftermarket distributor that fits the 232, 4.0L and 4.2L:  http://www.summitracing.com/parts/sum-850047?seid=srese1&gclid=Cj0KEQiA6IC2BRDcjPrjm_istoUBEiQASrLz1r8PW3l_sI5HQ2vvV6efx_VzBhcw2jHkJwgLv2vGERkaAgpx8P8HAQ.

Note:  If you were concerned about distributor fit and shaft or housing dimensions, compare the height between the camshaft drive teeth and the block deck where the distributor housing sets.  This measurement should be the same between a 4.2L and 4.0L.  You need the distributor's drive gear to engage the camshaft's teeth properly when the distributor housing is in position and clamped down. 

A new distributor housing base gasket should come with the distributor to seal the housing in the block bore.  The 4.2L and Renix 4.0L engines use the same part number for the distributor base gasket and the clamp.  You'll need a distributor clamp that fits properly with the base of the HEI distributor housing.  Your 2.5L distributor clamp is also the same part number as the 4.2L and 4.0L Renix engine.

Looking forward to pics of how this is unfolding...

Moses

Edited February 15, 2016 by Moses Ludel