Nucking Futs
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Thanks Moses. I have Howells TBI kit, and I do not have emission requirements on my Frankenstein Jeep. The engine is an 84 so that is how I define my Jeep since this is the heart of the performance. While I cannot say money is no object, I can afford either a stock rebuild, or a 4.6L stroker or V8 swap. I am cognitive of cost and exercise discretion when it comes making these kind of changes. I will ask a lot of questions, ponder for weeks, and act slowly on my decision. It took me a year before I removed the T5 and installed a Ford NP435 (feels at home in the Jeep). My baseline data is the 4.2L. I started with a stock 4.2L with the BBD feedback carb, did the Nutter Bypass with Ford big-cap rotor, added MSD CDI, then the TBI. All changes made improvement in drive ability and reliability. The TBI was by far the best improvement. Not necessarily performance increase in HP and torque (some though), but rather made her very reliable and drivable. Highway speeds have been my problem, and as you noted with the 4.2L head issues, is exactly what I experienced driving on the mountain roads. I know the 4.2L can do better, as I have to back off the throttle because of pinging. With this knowledge, I think you answered an obvious question that I failed to see. The head will contribute more towards drivability. This is a performance increase in itself and will be worth the expense alone. So, if I keep the 4.2L, she will at least be getting a 4.0L head. I better start looking at short tube headers now too. But a 4.6L stroker with an increase in bore diameter. Hmmmm...............Haha, there is no replacement for displacement! Which makes me chase the V8 swap idea too. Thank you again sir. -
The 4.2L is done. Blow-by in crankcase is so excessive now, the increased pressure cannot be managed any longer. Time to pull her out for some major surgery. I am considering the 4.0l head swap, but I am not certain that the extra cost to swap the head is going to help that much to justify the cost. I understand the 4.0L head flows better than the 4.2L head, and is overall a better design. I would like a little more top end power without losing the low end grunt. But.....when I see HP and torque numbers on 4.6L strokers (or a 4.2L with 4.0L head), it is always around 2500/3000-5000 rpm. This is way outside what I care about. I would love to see what the power band will be from idle to 3000 rpm with the 4.0L head on a 4.2L (or a 4.6L stroker). I am not looking for a power monster, just a little boost. I would hate to spend money on a new head, exhaust manifold, and exhaust system, only to find out that it really did not add performance increase where I want it. Does anyone have some useful information they can share? Real data would be optimal, but anything would help. Will the head swap help below 2500 rpm to warrant the cost?
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Compcams 252H, got it! My mistake on the 264H. Thank you sir. I do appreciate the all the advice.
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Thanks Moses. My next journey is to find a quality builder. I do want to have the engine balanced. From my understanding, it will smooth out the engine more which will also aid in prolonging the overall life of the engine, a worthy investment of cost. Searching the internet I have found several business that offer new casting 4.0L heads, and others that prep the head for the 4.2L. Hesco still makes their 4.0L head, and there is always Edelbrock's head. The later two are expensive, and I don't want to blow half the budget on just the heads. I will be visiting the local auto recycler yards in search of intake and exhaust manifolds. I will need to contact Howell about the O2 sensor locations between the 4.2L and the 4.0L stock locations. I don't think it will make a significant difference, but I am sure they will know. I do have a question about cams. I know you previously were a proponent for the Comp 264H grind (I believe that was the one) from one of you videos you made. Considering that I have the Howell TBI and the associated MAP sensor, what differences in cam profile are needed for the TBI system? I drive and live in the low to mid power band, I generally keep the engine under 2500 rpm. That is the sweet spot of the 4.2L. More to come and I will post progress as it happens. One good outcome from all this is I will have a fresh new rebuilt engine.
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Hi Moses. I think the wind was sucked out of my sail after my last go around with the Jeep. Not as good of news as I was hoping, but could be worse. The engine still runs at least. Here is the report. With the valve cover off, I visually looked to see TDC for #1 and went around several times and tested at both positions just to make sure. I did observe the rotor for a last double check. I watched for the rockers to stop moving, and wiggled them to see if there was any tension on them. No tension present with just a slight twisting from my hand on the rockers at TDC. Looking at the timing mark at TDC, it appears that the valves are closed when they are suppose to be. When I did the leakdown test, the engine did not spin, another indication I was at TDC (if I am not at TDC the engine will spin forwards or backwards as I apply 100psi). Sigh! I still have ~45% leakdown. This is disappointing. I was hoping for a simple timing set replacement. Kind of weird that compression numbers where so high with that much leakage. I would say one of the gauges is wrong. Since I can hear air escaping into the intake manifold, I would bet the HF compression gauge is likely off. I need a new timing sprocket/chain this I know. I also have an internal vacuum leak via the intake valves, this I know. The leak could explain why it wants to idle a little higher. The spark knock I would say is from the excess carbon. I thinking that my cylinder head needs servicing, more than I can do. Either carbon is hold valves open or the issues with stem and/or seats, and likely a combination of all of these. If my cylinder head does need work, doing just a top-end rebuild doesn't make sense with 170,xxx miles. I was always taught this with speed accelerate wear on the piston rings. I have some thinking to do. In the meantime, I would like to hear your analysis Moses.
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Moses, at this point I would say anything is possible! What I do know. I have an C-block with serpentine belt drive. The timing cover has the magnetic probe socket. Is the V-belt cover compatible with the serpentine belt? Pulling the valve cover may be best option at this point since the possibility of mismatch parts is plausible. While I don't think this has happened, I need to verify this to rule out uncertainty. I employed the visual method of looking through the spark plug hole to find TDC. I know that there is a moment when the up-travel stops and the crank is still spinning . How many degrees am I off from true TDC I don't know, but I am close enough that the valve is suppose to be closed at this moment. Looking at the timing mark it is around 4* before and valve is open. If I rotate the crank to the TDC, valve still open. Past TDC and the air pressure will push the piston down. If I try 8* before, the air pressure will spin the crank backwards. Because I am looking at TDC for timing and not the timing mark, this is why I am thinking there is cam timing error. The stretch in the chain has me thinking the chain jump may be a real possibility. So I will pull the cover off and verify when the valves are closed according to the rocker arms. I can then see where the timing mark is. If you know approximately how far off the IH cover is from the Jeep cover that would be helpful. For creep, I'm probably on my own. Inspection of damper when timing gear and chain is replaced may tell. And the Jeep passes smog with no issues btw. The tool looks like a winner and will add it to my collection. In the meantime I have some work to do.
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Quick lunch break test. Timing mark set at TDC. #1 cylinder visible through spark plug hole. Rotor pointing towards #1 position on cap. #1 has 45% leakdown with air moving through intake (sound adjustable by opening butterfly in TBI). Without rotating engine, I removed the hose and tried #6 to see if I was on wrong cylinder. #6 had leaked also. I tried various positions on the timing mark to see if I could find where valve was actually closing. I could no find it as psi pushed piston either backwards or forwards depending on position in stroke. I tried putting a wrench on the crank nut to lock crackshaft from moving, but I had moderate success doing that and still had leakage. I need an extra set of hands! The only way to positively know when valves are closed will be to remove the valve cover off. I may do that later. I decided I would try something a little easier and see how much stretch is in the timing chain. I rotated the engine all the way around to take up slack and I set timing make to TDC on timing cover. I then rotated the crank back until the rotor moved. It took between 3/4rd" to 7/8th" of an inch of movement on the dampener before the rotor moved. That is past the 5/8th" you mentioned. Considering the slack in the chain and my valve closings do not seem to match TDC I am still thinking: (a)-the chain is unable to keep time because of the slack, or, (b) chain jumped and is out of time. I can verify #1 intake valve closing and opening by pulling off the valve cover, rotor through the cycle, and note the position of the crank timing mark in relation to the #1 intake valves opening/closing. But is that really necessary and worth my time with that much slack in the timing chain? I think doing anything else it is an exercise of futility. As you stated, compression numbers are good. Even if the numbers are off 20%, they are still good. I know I need a new chain. In a real simplified way, I see the compression test indicates that my engine is holding air just fine. The leakdown test says I have a timing issue in relation to the movement of air at the correct time. I don't know 100% though. I'm not a mechanic, I just play one on the internet :D.
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Moses, I'm pretty sure I did it correctly. If the timing mark is on TDC, #1 is up to top, the rotor is pointing to #1 plug wire, I should be on intake stoke, yes?. #1-6 are paired but #6 at exhaust and #1 at intake I understand. #2-5, #3-4 are paired if I recall correctly in the same manor. I did follow the firing order, noted where the rotor is in relation to the cap for firing and position of cylinder. I can redo the test to verify, as it is pretty easy to do and will not hurt doing it again, but will have to be after work tomorrow. I will also try rotating the crankshaft back after I stroke is on #1 TDC to check total distance to timing mark travels before rotor begins to move. I hope I did the test wrong.
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Correction, the cam timing is retarded (intake close timing is delayed). Valves are still open at TDC. I don't hear slap or rattle form chain. Intuition is telling me this was done on purpose.
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Every cylinder same results, 40-50% leakage through intake. If I run crank till valves are closed, the air pressure runs to the engine to the next cylinder and reads 100% leakage. I've always thought my cam was not in time for a few years now. That is now confirmed. Why is it is the mystery. I suspect someone has been in there and done some engine work. Block and head are not stock looking color, valve cover has been replaced with an aluminum cover (not really a good one but it shows someone was dressing her up), odds and ends. Compression is pretty darn good for a 170xxx 4.2L being over stock specs. My hypothesis (not geometry) is a rebuild. Maybe the head was shaved too bump compression chasing a few HP? New cam profile timing chasing top end HP? I have no idea. Or maybe the chain just jumped.
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#4-50% leakage, #2-40% leakage, all through intake valve. Odd. Run up to #1 visually into cylinder as I rotated by hand and I could see no cylinder movement as I rotated crank. Timing mark is at 4* before TDC. This would make sense as I tried 4* and it backfires through the carb. So it appears that my valve train is not in time and advanced about 3-4*. Now, is that from chain slack and it jumped, or because someone has been in there and tried some "special" timing. I'm going to see what I can do for the rest of the cylinders.
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Kit is here with adapter. Charging compressor and will start the test today.
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The adapter could have been missing. I hope this one will works. So I have an 1971 DJ5 that I acquired a while back. It was cheap, has lots of issues. Anyways, I thought that pulling the head from the DJ would be a good practice run to see what it will be like pulling the head of my CJ. The bolts are bolts, you turn turn turn them. But lifting that monster of a head off the deck, dam! That head is a beast! WD40 seems to loosen carbon reasonably. Add some elbow grease and brillo pads and it works wonders on removing carbon. So cleaning the carbon won't be too bad. Removing the head will be a chore. Installing the head, that will be a challenge without damaging the head, mating surface, the gasket, my fingers, back, or some other part of my body! A hoist would come in handy for this job.
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Looks like what my second order is but with different name. https://www.amazon.com/5573A-2-Gauge-Cylinder-Leakage-Tester/dp/B000OUX9PO/ref=sr_1_19?dchild=1&keywords=leak+down+tester&qid=1619479896&sr=8-19 We shall see.
