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Propane injected 4.7L Stroker


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I guess I could have chosen a few different parts to make this a little easier on myself when it comes time to installing the engine in my Jeep, and being able to figure out how I'm going to run all of my accessories once it's all in, but I guess that's what makes it custom.

 

Here is the run down:

99 or 00 WJ 4.0 block

04 TJ TUPY revised 0331 head

4.0 connecting rods

AMC 258/CJ7 4.2L crank

Keith Black forged pistions- IC945-060- .060 over with 10.80cc dish

COMP Cams 68-232-4 Cam

COMP Cams High Energy Timing Chain Set - 3219

Mopar Performance 0.043" Head Gasket - P4529242

Clifford carburated 4.0L intake manifold

GotPropane.com conversion kit

 

I decided to go with the 99+ Wj/00+ TJ block originally because I had intended on building this for a 00+ TJ, but plans changed. I decided to stick with it for several reasons, ease of installation was not one of them.

For starters, it was free. It had been swapped because the previous owner had failed to change the oil for quite some time, causing sludge build up, so bad that eventually it spun the #1 rod bearing due to lack of oil.

It had enough miles on it that the block is close to whats called a seasoned block. After several years/miles of being heated up and cooled off, an engine will shift and distort as molecules realign themselves through a slow heat treat process, causing parts to not quite line up as perfectly as the day everything was machined. Lots of engine builders prefer old, high mileage engine blocks over a brand new one, for this very reason, believing after you go through and bore it out, deck it, and line hone it, you are not going to have any more movement since they are starting with a block that has already been heat treated, and everything has settled.

The 99+ WJ and 00+TJ blocks are a little different than the earlier style, and has a lot thicker castings around the cam shaft to fix a problem with the cams shaking themselves apart at high RPMs(higher than most factory 4.0s will ever see, but none the less), and have thicker cylinder walls, able to support up to .080 over, safely. Both may not be needed, but better to have it and not need it, than need it and not have it.

 

I wanted the head because, despite how everyone says the older heads flow better, I like the late model exhaust headers better, and since I'm doing all the port work myself, I'm confident I can open the exhaust ports up enough to make them flow similar numbers to the older heads. That and the head only has 13,000 miles on it. Yes I know that goes against the logic of using a seasoned block, but this way I don't have to have a bunch of machine work done, and if it gives me any problems, I'll just upgrade to a Hesco aluminum head.

 

Why Propane?

Originally I wanted to build this motor to put in a 00+ TJ with the coil ignition, and run it on E85, but I decided to build a Comanche instead. Well the Comanche has the old RENIX FI system, and I'm not a fan of it, too many quirks, and I still don't like that it has an EGR valve. I could do a HO swap and update everything to OBD 1 or 2, but then I would have to cut and splice wiring(I hate wiring!), and I would still have to fight a computer tuning the engine.

With Propane, I pull out all of the computer controlled stuff and bring it all back to a carbureted style setup, using a propane injector in place of a carb. Clean, plain, simple, easy to work on, easy to tune, and for as little as this will be driven over long distances, it will work for me.

 

Now for the pics:

 

The donor block

#1 rod journal

Sluge build up in the timing cover

The oil filter

 

4.2L Crank

I was really trying to get a crank from a carburated YJ, since they have the short snout, but due to a mix up at the shop I bought it from, didn't have one to sell me, so they threw in the spacer for free.

 

Keith Black forged goodness

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Block and head just got back from being thermo blasted today, stripped the entire thing down to the bare cast iron.

 

This should make working on it a lot more enjoyable, especially with how sludged up the block was.

 

Spent part of class going through and tapping all of the bolt holes out, this will make it a lot easier to assemble, and ensure I don't get any false torque readings from boogered up threads.

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if you want to make instalation easy call brown dog offroad up and order theyre superheader bracket kit S2883. its not listed on the website and is a custom kit for clean sheet blocks going into a xj/mj. so far they have only made 3 of these, you can be the 4th :wrench:

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if you want to make instalation easy call brown dog offroad up and order theyre superheader bracket kit S2883. its not listed on the website and is a custom kit for clean sheet blocks going into a xj/mj. so far they have only made 3 of these, you can be the 4th :wrench:

 

That is awesome news, I've been trying to figure out how I was going to pull that off, no way this motor is going in with the stock engine brackets after seeing two blocks go to scrap because of broken bolt bosses. The first being the engine that donated my 0331 head. Was figuring I would have to either make my own, or call up M.O.R.E., Brown Dog, or Liquid Metal Industries and see if I could get them to send me somewhat of a DIY kit.

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the number i mentioned was a complete kit for the wj/tj block into a mj. bought the kit for mine, comes with block brackets/motor mounts and meteric hardware. i got the super flex mounts for mine and there is a noticable vibration, have one more thing to try (think my tcase is mounted low and binding the motor mount bolts causing the vibration) then ill go back to a stock rubber mount because i like a smooth ride. i can't say enough good things about brown dogs customer service, and if your a NAXJA or jeepforum member you get 10% discount

 

 

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the number i mentioned was a complete kit for the wj/tj block into a mj. bought the kit for mine, comes with block brackets/motor mounts and meteric hardware. i got the super flex mounts for mine and there is a noticable vibration, have one more thing to try (think my tcase is mounted low and binding the motor mount bolts causing the vibration) then ill go back to a stock rubber mount because i like a smooth ride. i can't say enough good things about brown dogs customer service, and if your a NAXJA or jeepforum member you get 10% discount

 

Yeah, I've helped a buddy of mine put the Brown Dog engine brackets on his '05 TJ, and then put Super Brackets on when a couple of the passenger side bolts broke, leaving one bolt holding everything in. I strongly recommended upgrading them since he didn't know how long he had been driving on it like that, and that bolt boss was surely fatigued.

 

question: did you stroke the 4.2 crank? or did you just use the stock stroke?

how much did this setup cost minus the propane conversion.

 

Stock 4.2 stroke. Right now I have about $900 into it for the crank, cam, timing set, and pistons, and it was $140 to thermo blast the block and head. The block was free, he just wanted it out of his way. The head and connecting rods came from an engine I bought for $150, then I turned around and sold the crank, oil pump, and A/C compressor for about $400, I'm not counting the head and rods as a cost or money made.

 

I have not bought the rest of the valvetrain yet, I'm going to buy all that and my ARP hardware once we figure out what will work best. As far as the oil pump and all of my gaskets, I work at O'Reilly and get all of that stuff for a great discount, but I will try and keep somewhat of a running total as things progress.

 

If you're going to run just propane, and never run it on gasoline, have you given any though to upping the compression ratio? Propane in an engine set up for gasoline will make less power than gasoline. And it has an octane rating of 110.

 

Been there already, like I said above, when I had started gathering parts I had planed on this being a fuel injected motor and was going to run E85. The Keith Black UEM-IC944-060 piston has a 21cc dish, I was looking at around 9.6:1 compression with those. I went with the UEM-IC945-060 pistons with about a 10cc dish, I'm looking at about 11:1 compression.

 

Based on rule-of-thumb mathematics, educated guesstimate on power is about 335 hp and 400 lbs/ft. When I say "rule-of-thumb", I mean the rule of thumb calculations for compression (on a naturally aspirated V8) is: For every one point of compression you go up, thats good for about 60 hp, for a 6 cylinder that'd be about 45 hp. With the 21cc dish K-B pistons I was looking at about 270 hp/335 lbs/ft so with almost a 1.5 bump in compression, my numbers sound about right.

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Spent a little time working on the head tonight. I've been putzing around with this head on and off for maybe a year and a half, I have about 60% of the intake and exhaust ports gasket matched and roughed in, as well as several of the combustion chambers roughed in. I finally got the #1-2 cylinder intake ports about 90% finished tonight, down to the final polishing.

 

Stock intake port

Ported and polished

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I'm not sure I'm satisfied with the roof of the bowl, there is a pretty hard turn at the back of the port at the turn down into the combustion chamber. With all of the material I removed from the valve guide, it makes the turn a lot more noticeable. Air doesn't like to make hard turns like that, really slows down air flow. A common way to take care of something like this is to use an epoxy putty to build the area up, and then grind into a more flow friendly shape. Not sure if I really want to bother with it though. Slow air means Peak torque will come on sooner,

 

Why? Peak torque happens when an engine reaches it's peak volumetric efficiency. The most effective description I have been given was like this:

 

You have two horse troughs, one filled with water and one empty, take a bucket and start taking water from one trough and putting it into the other, each trip you make go a little faster. Your peak volumetric efficiency is when you are going so fast you start spilling water when going from one trough to the other. On an engine it's when, during the intake stroke, the cylinder is no longer getting completely filled when the intake valve closes. There is a fine line on making power, Volume makes Torque, Velocity makes Horse Power. Large ports will deliver a lot of air at low RPM, but as RPMs increase, the air is moving too slow to keep up with the speed that the piston is moving. A smaller port won't deliver as much air at low RPM, but as RPMs increase, a smaller port can pull air through faster(think drinking through a 1/4" dia. straw, VS a 1/8" dia. straw), fast moving air carries more velocity. So when the piston reaches Bottom Dead Center, a large volume port will not have anything pulling more air through, but a high velocity port will have enough speed to keep moving air into the cylinder after BDC, all the way up until the intake valve closes.

 

Make sense?

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In other news, I've been emailing M.O.R.E. and Brown Dog about block brackets. Both of them say that they have what I need. For the complete bracket and motor mount, BD is about $75 cheeper, has free shipping, and a 10% discount through JF, but MOREs brackets hit more bolt bosses(7/8 vs BDs 6/7), and don't come in that ugly yellow. Here is what I've been able to work out, MORE is willing to sell me their block bracket just tacked together for a discounted price, making them a good bit cheeper than the BD ones. This also allows me to cut tacks and easily modify the bracket if need be. Although getting the motor mounts from MORE would wash any savings made by welding the brackets myself, so I will be going to BD for the motor mounts, I'll just have to sand blast the yellow off and repaint them before they go on the Jeep. In all, it will save me about $40 from buying everything from BD, and $115 from MORE.

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  • 3 weeks later...

After discussing my port work with one of my instructors who used to run the port work shop for Lingenfelter, and my instructor/machinist we came to the conclusion I need a bigger cam. With all of my schooling in port design being focused on race motor applications, even though I tried not to, I made my ports to move a lot of air. In combination with the idea of using the LS valvetrain, the desision was made that the 68-232-4 just wasn't big enough to take advantage of the work I had done/will be doing, so I'm looking at probably the 68-235-4, that will also give me a bit more mid range power. The 4-239-68 is a lot more radical cam, for more high end torque and compression that will be great for those "Hammer Down!" moments, but I'm not sure I want to go that radical just yet. We'll see once I get it running.

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  • 3 weeks later...

Block is still at the Machine shop, his mother has been really sick with heart problems the last few weeks, so he hasn't been getting a lot done around the shop, not a big deal since I still have plenty to keep me busy with the head. He is doing the work for free, so I wouldn't complain even if I wanted to.

 

Still porting on the head, intake ports are all roughed in, and most just need polished, I'll wait till after it gets back from getting all the machine work done, and can blend the bowl in to polish. Going to hit the exhaust and combustion chambers next.

Last side by side comparison.

 

 

M.O.R.E Bombproof engine brackets showed up, asked for them to leave them tacked, just incase I need to do any modifications to make the clean sheet block work in the MJ, if I need to make any modifications all I will have to do is cut a few tacks, rather than cutting entire welds.

 

I did end up ordering the COMP Cams 68-239-4 cam and lifter kit, and I did decide to run the LS1 valvetrain, just checking options as to where to get them now.

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