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Clifford/Howell TBI conversion on 1999 4.0 in an 81 CJ-8


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Moses,

I have 1981 CJ-8 in which I have installed a 1999 Cherokee 4.0. I currently have a Davis DUI distributor installed. A couple questions:

1. I purchased Howell TBI kit for this vehicle, a Clifford intake/adapter, Clifford dual out Header. I have the engine bare to the manifolds. Installing the header was fine, but Clifford wants the intake manifold dowel pins removed, a pain.  Can I oversize the  holes in the manifold in order that the dowel pins will not restrict positioning the intake manifold?

2. Will an MSD distributor fit without issues? I used MSD ignition with a stock Motorcraft distributor and it worked well in another Jeep years ago. I installed a MSD advance module with that system and it allowed me to travel from my home located at 7350 ft elevation  into town at 5250 ft. That setup worked exceptionally well. I know the MSD distributor would work, but is pretty pricey. Should I go back to stock or go ahead and upgrade the distributor? My interest is mainly for reliability.

Thanks in advance!

Paul

Colorado Front Range

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pesilfven...I'm unclear whether the Clifford manifold has enough flange area to enlarge and center the holes.  More importantly, dowels have a reason.  Apparently, Clifford is not concerned about a shifting manifold.  If the OEM dowels were not a snug fit into the 4.0L manifold holes, there would be less of a concern.  If the OEM dowels aligned the manifold and ports, removing the dowels or enlarging the holes would be a problem. 

If Clifford wants you to remove the dowels, they may design their manifold ports to match the head ports even with the dowels removed.  Share some photos.  I'd like to make sense of the parts relationships before commenting further.

You should have no problem with the MSD distributor and the MSD module.  Confirm which MSD box is compatible and recommended for use with the MSD distributor.  I really like your plan to use the timing module to vary the base timing and spark curve for altitude or octane changes.  

Curious...What led you to opt for the aftermarket Howell TBI conversion and MSD conventional (mechanical/vacuum advance) distributor over the 4.0L factory MPI system, PCM and distributor?  Was the issue engine wiring?  The need for a 4.0L wiring harness and mate-up to your CJ chassis wiring?

Moses

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Moses,

I agree with you and presented that very question to Clifford regarding simply opening the locating holes in the flange, which is large enough to be able to float the manifold somewhat. The manifold is actually restricted/guided by the exhaust manifold. They indicated that the only header that would work with this intake is theirs, which I'm good with (since I have one). I had considered simply cutting the dowels if it was that important. I think I will find out exactly where the intakes align before I do anything else by using and old intake gasket and doing a rub with some acrylic paint.

i previously used a 4.2 intake with an MC2150, but had to be a bit more adventuresome matching the intake to the head. It worked but ended up with leaks, so I had this setup and figured to use it. Clifford didn't have an adapter to an MC2150, they said that that carb wouldn't provide enough flow. They may be right. I also came across a piece of half inch Bakelite phenolic resin with plans to make my own adapter bringing the Clifford manifold and the MC2150 together. While I have this apart, I think I'm going to make the adapter anyway and just to have it. Who knows what will happen.

To answer your questions, I obtained a sub-1000 mile 4.0 from a Chrysler corporate vendor in 1999 and finally, two years ago installed it in my CJ behind a T-176/D300. Pretty simple. At that time I did my rigged MC2150 since I didn't get the factory injection, wiring, the manifold was designed for port injection, so I couldn't use that with a carb. I then started  planning for the Howell unit because of the simplicity of GM injection. I have had several Jeep Cherokees and some issues with factory injection. I could have dealt with wiring, but the Howell unit is basically a three wire interruption into the CJ harness. Add in the availability of GM parts, so on and so forth. I live in Colorado and spend a lot of time in the mountains which are basically out my back door, and I wished to keep things as simple as I could. To me, nothing is more irritating than being way out in the mountains and having a breakdown, even if it's simple, but much worse if it's complex. While I never wheel alone, a strap tow of 20-30 miles is not fun.

I do have a Davis Unified distributor installed, but really liked the MSD timing control setup, so I'm considering the switch to the MSD distributor in order to have that option.

I really appreciate your willingness to spend this time with my project. Any time your name comes up, I come to attention.

Thanks,

Paul

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This all makes sense, Paul...Given that you don't have OEM EFI/MPI or the wiring harness, an MPI distributor and PCM, etc., the Howell TBI conversion kit is a great alternative.  You have the added advantage of altitude compensation for your 'Fourteener forays and other Colorado runs.  Off-the-shelf GM 4.3L componentry is helpful, too.  The simple Howell wiring hook-up is frosting on the cake!  

Either distributor (DUI or MSD) would be good, the timing control is a clear asset.  Actually, the Motorcraft 2150 is adequate enough.  The two-barrel Motorcraft carburetor on our '87 Grand Wagoneer 360 V8 worked flawlessly.  It even had a mechanical altitude compensator, though nowhere near as refined as EFI or the Howell TBI with an O2 sensor and the ECM.  A 360 AMC V8 Motorcraft carburetor would be an inexpensive alternative, but your Howell system takes the fuel system efficiency to the next level!

Thanks for sharing and clarifying.  Your CJ will be very reliable and trail/road worthy when you complete the Howell EFI/TBI conversion!

Moses 

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Moses,

Quick question: Should I use a MC2150 with a 1.08 or 1.16 venturi? Latter was used on 304 V-8s (according to several people) or modified 258s. I was told that the Motorcraft 1.08 doesn't work on Clifford manifold due to low CFM's by Larry at Clifford, they don't provide a suitable adapter. The manifold does have a somewhat larger internal volume compared to a stock 258 log manifold. and, of course, I'm working with a 4.0, smaller displacement. I'm moving forward on my MC2150 1.08 , I'll try it and wait to see what you think is best.

Thanks, Paul

 

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Paul...A 2150 carburetor that I really liked had plenty of CFM.  If this manifold requires more CFM than the 304 V8 unit (your bore stats), there's the 5RHA2 version of the 2150 Motorcraft found on later 360 V8s in Grand Wagoneer models.  Throttle bore size is 1.562".  Main Venturi size is 1.21".  It has an "Altitude Compensator" (Aneroid) and a throttle solenoid.  I did a textbook rebuild of our '87 Grand's version of this carburetor with great results:  instant starts with the choke set right, plenty of air/fuel on demand and seamless altitude compensation.  This carburetor, adjusted to factory specification, is undetectable from EFI performance.  However, it's calibrated for a larger displacement engine.

That noted, the CFM flow might satisfy your open Clifford plenum.  Is that more flow than the 4.2L/258 engine needs or can tolerate?  The 1.08" 2150 flows 287 CFM.  The 1.21" flows 351 CFM.  I'm guessing the 1.16" is an Autolite/Motorcraft that flows around 300-310 CFM.  (Do you know the engine application?)  Glad you started with the 1.08", a good benchmark for your 258.

I'm not concerned about the jetting on late emissions carburetors like the 360 V8.  The concern is venturi size.  I could never get a universal 500 CFM Holley 2300 series 2-barrel to work with a 258 (way too much carburetor).  The smaller, universal 300 CFM Holley was also problematic but for other reasons.  For the record, my Holley pick for the 258 Jeep engine was a stock replacement I-H 266 V8 2300-series carburetor.  Off the shelf or found on an original I-H engine, this was my choice.  They were used in the sixties with manual and automatic choke versions.  I have the Holley tag numbers.

As a rule of thumb, I look for a carburetor that fit an engine close to my engine's cubic inch displacement.  That's how I isolated the I-H 266 V8 carburetor for a 258.  I know that a stock 258/BBD two-barrel intake manifold with an adapter to the I-H 266 V8 Holley 2300 carburetor does work.  You can try the Motorcraft 1.08" or 1.16".  Either should be a prospect if originally from an AMC 304 V8.  An Autolite (essentially a 2100 Motorcraft) two-barrel for a vintage Ford 292 Y-block or 260 and 289 small block V8 would be another possibility. 

In my experience, Clifford manifold/carburetor combinations begin with a 390 CFM carburetor or larger.  Camshaft profile is another concern with your Clifford manifold's open plenum design.  Essentially, this manifold works with the Clifford header and performance camshaft.

Altitude compensation and jetting are always considerations.  The later 360 V8 carburetors addressed that issue with the mechanical altitude compensator.  Let us know how the 258 performs with the 1.08" 2150.  We'll go from there. 

Moses 

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Moses,

I light of your comments, It seems I'm into unknown territory. This project has always been the ability to carburete a 4.0/242 cu in Jeep engine. From the factory, it seems that the engineers went with FI and the third partys never considered anything else. Makes sense to me. My interest in carburetion was based upon the anticipation of being able to do field repairs in areas where I might be stranded off-road. In light of info you provided, and my engine being smaller displacement that the 258 (242 cu in), I'll keep trying with the current plan. I already had the combination of a 258 manifold/ 1.08 Motorcraft/4.0. running quite well. Obviously, I'm in a little over my head, but that seems to be my nature. Let's call it an educational challenge. Had a thought. Perhaps a stroker to 4.6/4.7 bringing the displacement closer to 5.0 L might be better suited to the Clifford manifold. I have a 1980 258 sitting here for a crank, I think that has the required short snout. That's novel, rebuilding an engine to fit a specific manifold, hahaha.

Perhaps there's something here that someone else can use. I certainly appreciate all your help and I'll touch base with you as the project progresses.

Paul

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Paul...I have no problem with the carburetor approach if done right.  You do have the altitude challenge at Colorado.  That means jetting issues with a carburetor.  Some carburetor designs are less altitude sensitive.  A spread-bore Quadrajet GM carburetor is actually one of my favorites.  There was a 252 Buick V6 application for this carburetor, somewhat rare but suitable.  Also, there were 305 Chevy V8 uses of the Quadrajet, again in step with my mantra about "find a carburetor from an engine with similar displacement".

The stroker crankshaft is always an option with many gains and nothing to lose.  And yes, that would make tuning with the Clifford open plenum manifold a bit easier.  A 305 Chevy V8 Quadrajet, a 390 CFM AFB or an Edelbrock carburetor for a small V8 would work here.  You also have the Motorcraft insights to consider or the Holley 2300 for the I-H 266 V8 that I described. 

Your most significant challenge is the open plenum on the Clifford manifold.  No matter how many "barrels" you choose, they all feed simultaneously into that open plenum.  That's not how two- and four-barrel OEM manifolds work.  This is also why I stayed with the stock BBD 4.2L manifold and used an adapter to mate the Holley 2300 two-barrel (I-H variety).

Jack Clifford held national drag racing records and understood how to increase inline six-cylinder power.  Jack and I discussed his engineering in the eighties.  The most significant feature of your manifold is its ability to flow air/fuel mixtures more uniformly to the outer cylinders of an inline six-cylinder engine ("ram" flow).  That's big.  Stock manifolds inherently lean or starve the outer cylinders of longer inline sixes and straight eights.  Jack's aim was performance, which included a higher lift and longer duration camshaft and a header.  This helped mid-range and top-end power—not the tip-in throttle smoothness needed for rock crawling.  This manifold is purpose built for a specific performance gain. 

Keep us posted!

Moses

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Moses,

I appreciate your input. Quick question, Holley has a Sniper kit specifically for Jeep 258's. I'm still playing around with possibilities. Since I also have a stock BBD 4.2 manifold now installed (The dowels actually located the intake by setting the outside of the manifold flange on top of them. The 4.0 being a high port manifold) and the Sniper kit is set up for that BBD manifold. What is your position regarding this EFI system?

Thanks,

Paul

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pesilfven...Do you need to do an emissions inspection?  Does this system have a California E.O. number?  Beyond that, I've not installed a 4.2L manifold on a 4.0L head.  The Mopar EFI conversion went the other way:  A 4.0L ('95 YJ Wrangler prototype) intake manifold was fitted to the 4.2L. 

The Sniper and MSD Atomic have been around for some time.  We followed an Atomic EFI retrofit to a 4.2L at the magazine several years ago.  Again, no E.O. number, but it worked and had a clean tailpipe reading.  The Atomic EFI was adapted to a stock 1989 4.2L BBD manifold:  https://4wdmechanix.com/?s=Atomic+EFI.  This is a 4-part series, detailed, that will walk you through some of the obstacles overcome. 

We took the vehicle over the Rubicon Trail (also covered at the magazine).  However, despite the clean tailpipe that met low emissions, the system was abandoned due to lack of a California E.O. number.  The YJ's owner subsequently installed a complete 1991-95 era 4.0L MPI/EFI donor engine with PCM and peripherals.  He passed California smog as a legal engine conversion...It all depends on your aims and emissions requirements.

Moses

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Moses,

In my County in Colorado, a 1981 vehicle requires an emission inspection, but only an idle tailpipe check. My Howell kit does have an E.O. number. It also came with an adapter for a 258 intake. Glad not to be in California. Anyhow, a number of years ago when I first installed the 4.0, I had a new exhaust fabricated. At that time, I neglected to closely inspect the system and a couple days ago, I realized that the shop also included a cat converter. So, I'll install as if I were in CA utilizing all the required emissions pieces. I'll have to get a vapor can. I will photograph this procedure and send them along if you have interest. Incidentally, when I completed the prior 4.0 install with the MC2150 about 6 years ago, much to my surprise, it ran quite well. I'll do better.

Thanks,

Paul

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pesilfven...Your photos of the install will be helpful to others.  This is an unusual project with the 258 intake, Howell EFI and the 4.0L cylinder head.  Make sure you have good intake port alignment/match-up.  You're essentially creating a CA E.O. install with a 4.0L long block engine.  This will be interesting for others to see!  

The Howell system should make a noticeable difference in performance, electronic altitude corrections (with the 02 sensor feedback) and improved fuel efficiency.  TBI is good for low end torque, and that's your CJ's realm.

Have a pleasant Holiday Season and keep us posted...

Moses

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