Eagle

I agree. The CAD on my '88 XJ failed once, a number of years ago. Naturally, I was in a valley trying to climb a hill in a snowstorm to get home. I replaced the vacuum harness, and I have a spare that's still new in the factory packaging, but knowing that there's no downside to eliminating it, my choice today would be to just lock it in the engaged position and not worry about it.

You don't have automatic hubs, you have (as already commented) a central axle disconnect. It's a vacuum-operated sliding collar mechanism on the passenger side, between the differential and the outer stub axle. If you lose vacuum, the slider won't actuate. It can be engaged manually, but doing so requires crawling under the vehicle and removing the vacuum shift mechanism from the housing on the axle. There are no solenoids. It's not operated by electricity.

Here's a link to what I consider to be the most accurate chart of tire sizes and engine speeds with different axle ratios. I'm biased -- it's my spreadsheet. It's more accurate than most on-line calculators because I used actual tire manufacturers' revolutions-per-mile data rather than just calculating tire diameter, which doesn't allow for sidewall deflection when the tire is loaded. https://docs.google.com/spreadsheets/d/1pHFuhGgj6dQDfzyfFJH5z7NCDLW2KX3ABQgAJr3lBvM/pub?hl=en&hl=en&output=html Let's assume that a 4-banger originally came with 4.10 gears and 205/75-15 tires. Well, we can't check that, because I didn't go that small, so we'll use a 215/75-15 as the stock tire. Find the column for 4.10 gears, and we can see that at 70 MPH in 5th gear the engine turns 2705 RPM. So now we want to see what comes close to that with 31" tires. Scroll down to the section for 31x10.50-15 tires. We find that with 4.56 gears, at 70 MPH the engine will be turning at 2713 RPM. That's a difference of just 8 RPM from stock. Not worth even worrying about. That's the difference between new tires and tires that are 50% worn. If you want to jump to 4.88 gears, then we see that at 70 MPH (in 5th gear) the engine would be turning at 2904 RPM. That's faster than stock, but not that terrible. Remember, the 2.5L and 4.0L engines are basically the same design. They both were developed from the original 232 c.i.d. engine that AMC introduced in 1964. Back in those days, cars didn't have overdrives -- they were mostly 3-speed manuals, or basic 3-speed automatics. I had a 1966 Rambler American back then. With stock tires and stock gearing, it turned exactly 3000 RPM at 72 MPH. And those engines typically ran for well over 200,000 miles. So getting your 2.5L up to 2900 RPM at 70 MPH isn't going to hurt it. Just keep your oil clean and fresh.

These are critical questions. You can't go much deeper with gears. You have 4.10s -- if you go with Dana-Spicer gears, there's only one more step: 4.56. You can get 4.88s if you go with aftermarket gears. But a lot depends on what you want to do with the truck and what size tires you run (or plan to run).

The 4-way hazards use a separate flasher from the turn signals. You probably need a new flasher for the turns. You also may have one or more turn lights burned out, which will lock up the standard flasher (unless you have a heavy-duty flasher such as used in the trailer tow option). As to the dash lights, have you tried rotating the headlight knob? It's a dimmer, and all the way in one direction (I've forgotten which way) turns them off completely.

Did the crank position sensor (CPS) get damaged or disturbed during the swap?

Power does not come directly from the battery. You may have misunderstood something you read. The blower has four speeds. The lower three speeds are controlled by different resistors in the resitor pack, but high speed doesn't flow through a resistor. That's why if the internal fuse on the resistor pack blows, you have high speed but no lower speeds. BUT ... the fan doesn't run even on high speed when the ignition is turned off, so the power does NOT come direct from the battery.

An open system needs an expansion tank. If the MAC's aluminum tank had been available when I did my '88 XJ, that's the way I would have gone. But ... it wasn't, so I used a Moroso aluminum surge/expansion tank from a local speed shop. It's also sold by Summit racing. I run it with an overflow bottle:

Relays don't lighten the load on the electrical system. Ultimately, whatever component you're switching uses however much current and power as it needs. What relays do is reduce the current through the switch(es), and if properly located they also reduce voltage drop.

Numbers don't lie. The minimum gain you can get from a SOA conversion is the sum of the axle tube diameter + 2x spring perch offset + leaf pack thickness. A D44 tube is what, 2-3/4"? The spring pack is another 1-1/2". and the perch offset is about 1/2" x 2. That's 5-1/4" ... minimum.

Castrol Syntec 5W30 in winter, 10W40 in summer.

Morons. If they were going to round off 2.7 to 3, why not round off 5.4 to 5 ... or 6? It's not like those gauges are finely calibrated, precision instruments.

I expected that the Canadian gauge would be in kPa -- that's what the FSM uses. Numbers are numbers, they are more precise than "halfway." That said, if max is 5.4 then straight up (the mid-point) should be 2.7. The U.S. gauge has a range of 0 to 80 psi, and the mid-point is 40. The quarter point is 20 and 3/4 is 60, with tick marks at the tens. The scale is linear, not exponential. The FSM spec for oil pressure (for the 4.0L) is 13 psi (89.6 kPa) minimum (warm) at idle RPM, and 37 to 75 psi (255 to 517 kPa) above 1600 RPM. 80 psi is 552 kPa. 75 psi is 517 kPa, so the FSM is just doing a direct conversion. 40 psi is 276 kPa. To convert kPa to bars, just divide by 100.

Pretty sure he uses a FAST fuel injection system in his MJ drag truck, not Renix. Check it out. :thumbsup: If he does, he has changed it. I know Bob personally and I did a bit of work on the truck and the engine while he was building it. It was pure Renix when he first completed it and started racing it.

What weight oil is in the engine, and how cold does it get at night where you live? It might be helpful if you give us the actual numbers instead of reading the oil pressure like a gas gauge.

Agreed. Bob Salemi is running one in an NHRA pro stock Comanche in Rhode Island. Basically it just needs bigger injectors for a stroker.

On V8s I always liked the 4-barrel because you had small primary venturis for economy, and larger secondaries for when you needed more airflow and performance. I vaguely remember seeing AFBs as small as 400 CFM, and I always thought that might be a good carb for a 4.0L. Does anyone make a 2-barrel that has a primary and a secondary, rather than two primary holes that are the same size and no secondary?

Chrysler also used to (and maybe still does) sell through the Mopar Performance Catalog an MPFI conversion for the 258 engines. It was basically the Chrysler HO system used on the 1995 Wrangler 4.0L, packaged as a stand-alone conversion. Hesco also sold one -- which might have been the same system. None of them are inexpensive. Mopar: http://www.mopar.com/assets/pdf/performance/catalog/19561_JeepPerformanceCatalog_v02.pdf It'll lighten your wallet by about three grand.

If the votage drop still happens with the blower on high speed, the resistor pack isn't causing it because there is no resistor in the circuit on high speed. I would pull your blower motor and check it out physically. When you get it out, there's a round "squirrel cage" blower impeller on the end that goes into the air box. Try spinning it by hand. It should spin freely, with no resistance (or almost no resistance). What you've got is a mechanical device with a metal shaft that rotates in two metal bushings (not bearings) that haven't been lubricated in25 years. It may be running dry at this point, and metal on metal doesn't work very well. It may be possible to dribbly some lightweight oil into the end with the impeller on it. The other end is sealed, but people have carefully drilled a small hole in the little bump where the end of the shaft is located so they can get a few drops of oil in there. Then cover the hole with tape or mastic or RTV. Just don't use too much oil, because you don't want it to seep into the electrical contacts inside.

I've been at this for well over 50 years and this is the first time I've ever heard of a switch to control air shock ride height.

The engine starts with all the bypasses, so of course you can get it running. Just be patient and don't break things while trying to fix it. How did your father "unhook" the ignition switch, and how did you bypass the fuel pump? You may have bypassed some important connections. First, are you aware that the key cylinder in the steering column is NOT the ignition switch? The actual switch is the thingie (technical term) shown in Hornbrod's post. It's at the bottom of the steering column, and the key tumbler connects to it by an operating rod. If that rod is out of adjustment, the switch may or may not function. IMHO you should either take your key cylinder to a locksmith and get new keys made for it, or just buy a replacement cylinder (it's a GM Saginaw steering column, so if you can't find one listed for AMC/Jeep, just buy one for a Chevy). Then check the ballast resister, as shown in Fernando's post. You could also check to verify that the fuel pump has a good ground, although being in Texas I wouldn't think rust and corrosion would be a big issue. One step at a time, and keep us posted on how it's going.

If you want to sell it, take it to the classifieds.

Not just a different mount -- a different bumper. That's not a factory Jeep Comanche bumper.

I agree that it's better to begin with a known good block and do your own build. When I was younger and doing my own engines, I sent the bare blocks and heads to a local shop to be steam cleaned, oil passages cleaned out, bored (if necessary) and honed, and new cam bearings installed. They also checked the head for flatness and trued it up if necessary. Then I brought the block and heads home and did the assembly myself. You'll need a piston ring compressor, and a package of plastigage for checking the bearing clearance. If you don't feel like lapping the valves in yourself, don't strip the head before taking it to the shop -- let the shop do the valve job. But every procedure you can do for yourself keeps $$$ in your pocket. Just remember that a 4.0L is long and heavy engine. You'll need an engine stand. Don't skimp -- buy a good one.

Unless things have changed, they're pretty much universal in fit. The difference is in the strength of the spring.