1988 Jeep comanche AKA the penny sniffer

[zebvance]

I’m currently working on a lot of wiring in the cab of the truck which I will post a update of when I’m done. This weekend I plan on taking the truck to Llano State park to go camping for the weekend. This past week I got it inspected, insured, and registered. It’s about a 4.5 hour trip, the longest trip I have ever attempted to take with the truck. Kind of nervous.
As soon as I get back I’m ripping the front axle and suspension and going to start on the lift. However, until then I still have some things that I have done over the past few weeks to get this tread 100% up to date.

I went ahead and gave the truck a FULL tune up. New plugs, wires, rotor, distributer, cap, and coil. Went a bit overboard on the wires, but I got a good deal on them. They are OML 10mm racing wires.







After some research, I realized why I had such bad blow by. The flute stems in the valve cover of the stock renix 4.0 sat way to low, sucking up oil and dumping it into the oil filter, just a bad design. Now, since I recently found I have a bad ring in piston #2 I knew that this would not fix the problem but hopefully help to contain the oil enough to get me by until the stoker build. So I ordered a newer style aftermarket cover that did not have the flutes in it. I have since put about 100 miles on the truck and NO BLOW BY!





And here it is all done!

[zebvance]

Next up, I wired up a little boom boom for the trails. I had a hard time finding a subwoofer enclosure small enough to fix behind the seats of the cab. After I finally found one what should fit I had to add some wood to the bottom of the box for it to sit level in the cab. I had a real problem trying to figure out how I was going to secure it and the amp in place without it rolling around. I was tiring to avoid screwing in to the back wall of the cab at all cost. So with some brain storming I came up with a idea. I went to harbor friend and got some of their bar magnets and screwed them to the back of the box. PERFECT! They stick to the wall of the cab and don’t move a inch! I also did the same set up for the amp and put it to the left of the sub. I don’t have any pictures of the amp right now but I’ll try to t get some tonight.
That’s not the end though… I have never been a fan of no name cheap electronics but this time I was forced into buying a no name brand because It came with a box that would fit the cab. Well once again I learned my lesson. 3 Days after I installed the 600 watt max “audio pipe” sub on an OLD 300 watt pioneer amp (not bridged), I blew it. Started smelling and them made some god awful racket. I just bought a 1500 watt max Pioneer shallow sub to replace it which I hope to get to tonight.

[Fredo]

Those 10mm wires are comical. No 4L in history has needed 10mm wires.

Also, you still have the blow-by, I promise. The baffles under that crankcase vent and breather are just slowing it down. The "flutes" as you call them are actually a good design and help evacuate crankcase pressure under high rpm/load. If your motor wasn't worn out, they would be functioning exactly as designed.

I remember a buddy of mine had a cherokee with 300k+ on it, and while it was idling you could loosen the oil cap and it would sound like you were opening a 2 liter coke bottle. Ran fairly decent, just a little low on power and a ****load of crankcase pressure.

How many miles are on your truck?

[zebvance]

Yea I only have about 100 miles since the mod so I still don't know for sure. I know because I have a bad ring in #2 I will still have some, just don't know how much. The way I came across my info about the flutes being to long was from a retired Jeep dealership mechanic. He told me that he worked as a head mechanic at a Jeep/ Chrysler dealership for 30 years and these renix 4.0s would come back to the dealership with 10,000 miles on them showing signs of blow by, when the motor was 100% sound. He said a service bulletin was released by Chrysler addressing the problems stating that the flute stems sat down to far on the head and sucked up oil. The fix was to trim a inch off the flutes and send them back on there way.

This is all wait he tells me. Real, or a load of ****, I don't know. But I don't know what reason he would have to lie about it. Any way I thought it was interesting.

[Fredo]

Well, don't take what I'm saying as gospel. I know the crankcase ventilation flutes work better at venting crankcase pressures than the baffles on most engines, but I could totally buy them being too long originally. I would think trimming them would definitely fix the issue if they are too long. To be completely honest, on a 4.0L, the baffles will work just fine. Where you get into really scrutinizing design on crankcase vents is on high compression, high rpm stuff, forced induction applications, etc. For a "stock" or "stockish" motor, it doesn't matter as much.

[zebvance]

Time to update some more.
I was able in finally install my altimeter/offroad cpu and a few other things like a volt meter. I ordered a blank switch panel change hole plate from dirt bout offroad and installed the Cpu in it with a digital voltmeter. The Camron Offroad CPU is pretty much just a neat factor. It tells you your tilt and roll, along with Temperature and Attitude. It also Tracks your total altitude. I wish I would have got the White LED display though, the red one I got is not the brightest.
The mounting holes in the panel were pretty hard to get looking nice and straight. To cover up the rough edges I just cut some vinyl decal material and stuck it on there. I plan on making a nice face plate soon not sure yet on what the game plan for that though. I will probably make it out of wood and fiberglass over it.

[zebvance]

While I was doing that I also installed two 3.5” speakers in the dash for better sound. I am really happy with the turn out and the sound in the cab now.





I also Installed a gauge/switch panel where the factory clock was, to put an Rpm gauge (which I had already mounted there, just drilled through the factory clock though.) One of the switches I wired up to more Courtesy/ Cab lighting so I could see better when looking for something in the dark. The other two switches will be for rock lights and cargo bed lighting whenever I get around installing them.



I also installed a new subwoofer because I blew the other one, along with a new radio and wired up sirius XM radio. Oh, and I replaced all dash light, center console lights with LED bulbs (Much better lighting!) Anyway here is the end result!!!!

[aggie4life]

Looks nice, good job

[zebvance]

looks nice, good job

thanks!

[zebvance]

Now on to the bad news.

I did all that work in preparation to take the truck camping at Llano State Park in Junction, Texas about 5 hours away. I got done with all the work on Wednesday and planned on driving the truck around for a couple of days to give it a shake down before I took it on the trip. With all the work that had just been done to it I thought I needed to. New rear main seal, distributor, engine ground, ground and power cables to the starter and alternator, and then of course all the upgrades I did inside. Well the thing was finally not leaking a drop of oil.

Sure enough, drove the truck to work Thursday morning, came out to it to go to lunch and noticed a oil leak. I immediately took it back to Car Docs hoping that they just didn’t do a good job installing the rear main seal and it would be covered under warranty. They called me back and said that both the rear main seal and distributer gasket was leaking again. He said the remembered about the low compression in cylinder #2 and decided to do what they called a “pressure” test and run it up the road. They told me that before he hit 30mph the crank case pressure was up to 3 PSI. They said they won’t replace the rear main seal again because the crank case pressure build up from the worn cylinder rings was the cause of blowing out the seals again.

To me it adds up when I think about it. Over the past two years every time I would replace a leaky gasket or seal and new leak would pop up from a place that was not previously leaking.


I ended up not risking taking the truck on the trip. But this past weekend I did attempt to see how bad the issue really was. I drove it to my buddies deer lease 100 miles away in Sheridan, Texas. On the way there the rear main seal and distributor gasket leaks got worse and worse, I also believe I developed another leak at the oil pan. From the trip there and back I lost well over a quart of oil. Not to mention I averaged 11.8 MPG on the highway…
I hate to say it but I have to call it. The engine is done for. No more Band-Aids. I still plain on getting the lift done to finish that project. After that I am going to start looking for a 96+ motor to build a stroker. I will buy the parts as funds allow and then drop the donor motor and parts off to a very reputable machinist that I trust doing the machining and assembly in my home town. I plan on leaving the current engine in the truck until the stroker is built and ready to drop in. Since it still can move under its own power I feel it’s best to do that if I need to move the truck from time to time.

I did consider a V8 swap also, but there are a lot things that offset the benefits of how cheaply I can get a SBC. Here is a list of major concerns with that.

- Keeping it cool.
I have seen plenty of these swaps done on Cherokees and I always hear the frustrating stories of trying to keep it cool in the small engine bay. The only way I have seen it work is with a $1000+ custom cooling set up. Which I don’t want to have to deal with

- Firewall Modifications
A good bit of fabrication will have to be done to the firewall to make the V8 fit.

- Mounting the Motor
It will take custom motor mounts not to mention I would need to plate the unibody around the motor to deal with the additional weight.

- Transmission set up
2 options, buy a high dollar adapter plated to keep my current transmission or buy a TH350 and a adapter plate to mount it to the NP231

- Computer Compatibility
I don’t want to even look into what it’s going to take to make the renix computer and SBC computer talk to each other.

- The want for a fresh engine
At the end of the day I want a fresh rebuild. So that will mean I will get the SBC rebuilt regardless.

All of these reasons add up to me not perusing it. I think It will end up taking longer to get the truck back running again, cost more than a stroker when it’s all said and done, and be more of a headache. All for what? When the stroker will be putting out the same numbers maybe even better than a stock vortec 5.3 or something.

I have started doing research on the renix 4.0 to the 96+ 4.0 HO motor swap and it doesn’t look that bad. The plan is to go with a 96+ because of the better flowing head, intake, exhaust, and bigger throttle body. I will probably get work done on the head or buy one that has already been ported and polished along with a better valve train. They run about $600-750. Or get the new all aluminum head that edelbrock just released for the 4.0, but it runs about $1500.00. In addition I will also have to buy a new header to match up with the 96+ exhaust ports. Also I pain on getting a bored 68mm Throttle body. I want this thing to have plenty of air.

As far as fuel goes, I’m going to need to get a better fuel pump and the hesco adjustable fuel pressure regulator along with ford #24lb+ fuel injectors depending on the size of the stroker. I will also like to get an air to fuel ratio gauge to dial it in, but I know they are pricy, if I have that though I should be able to get the mixture right by adjusting the resistance on the MAP sensor.
As for the build in all I would really like to stay under $3000.00 in just the motor. I know I can probably add another $1000 in injectors, fuel pressure regulator, fuel pump, header, and Throttle body. I think these are realistic numbers and might even come out under 4k total.

I would love to do a 4.9 stroker but I feel it will be more costly and problematic, so I will most likely just go the route of a 4.7. I haven’t picked out the recipe of the build yet because I want to get deep into some more research. However, I did talk to the person that will be doing the assembly and he said to stay away from Keith Black Pistons and Eagle cranks. Both of their quality has really fallen off. He said his experience with SCAT over the past few years has gotten better and better. I trust this guy because he has been doing this for over 30 years and has built hundreds of motors. Furthermore, from the research I have done I should at minimum be looking at 270HP and 300Tq with a stock 96+ 4.0HO head. I am hoping for more like 300Hp and 330Tq though. Which I think are possible numbers.

I’m sure I could attempt to throw this thing together myself and probably save a grand but at the end of the day I am willing to pay more to know it was built right by someone that has a good rep and a tremendous amount of experience.

With all that said….

LET THE FUN BEGIN!

[Sparling]

Need to forget the letters sbc, and learn LS1. If you have any decent fab skills it isn't expensive when you compare it to buying stroker kits, a 1600 dollar cylinder head, bigger injectors, etc. Not to mention all that work to a 6 cylinder and it will maybe make as much power as a stock v8?

It'll probably take more work, but I think in the end you'll be much happier, and have a cooler end product with an aluminum v8 than you would with a 6 cylinder. If you have any doubt go wheel with creighton in his jeep.

[zebvance]

Need to forget the letters sbc, and learn LS1. If you have any decent fab skills it isn't expensive when you compare it to buying stroker kits, a 1600 dollar cylinder head, bigger injectors, etc. Not to mention all that work to a 6 cylinder and it will maybe make as much power as a stock v8?

It'll probably take more work, but I think in the end you'll be much happier, and have a cooler end product with an aluminum v8 than you would with a 6 cylinder. If you have any doubt go wheel with creighton in his jeep.

Been there done that.. The end result was me upside down in a field with a car that was a few inches off the ground and was 1000 pounds heavier than my truck. I tend to act stupid when I have redicuilous amount of power under a heavy foot. I would rather not temp myself with a lot of power in a truck that has a super sloppy roll around corners and sounds really awesome when you hit the skinny pedal.

[KrazyKarl02]

Been there done that.. The end result was me upside down in a field with a car that was a few inches off the ground and was 1000 pounds heavier than my truck. I tend to act stupid when I have redicuilous amount of power under a heavy foot. I would rather not temp myself with a lot of power in a truck that has a super sloppy roll around corners and sounds really awesome when you hit the skinny pedal.

Well then, I guess you should just go buy a Honda Element.

[tommy53002]

Need to forget the letters sbc, and learn LS1. If you have any decent fab skills it isn't expensive when you compare it to buying stroker kits, a 1600 dollar cylinder head, bigger injectors, etc. Not to mention all that work to a 6 cylinder and it will maybe make as much power as a stock v8?

It'll probably take more work, but I think in the end you'll be much happier, and have a cooler end product with an aluminum v8 than you would with a 6 cylinder. If you have any doubt go wheel with creighton in his jeep.

X2. Swap on the cheap.. sure, stick with an I6, but with the money you are talking about spending... LX swap all the way. But... sounds like your mind is made up.

[zebvance]

Well then, I guess you should just go buy a Honda Element.

I heard hippie chicks did Elements.......