"I've Got A Theory Of What's Wrong, But Can't Find Out Why It Does It." 

Just a thought here because I have seen it before but in a small block. Where the oil galley allows oil to the lifters. If the machining or casting for that block isn’t correct, the shouldered area on the lifter will sometimes not be able to get relief and never not be fully pressurized. For me it led to bent pushrods. The machine shop found it after a long long run of destroyed parts. Lifter bores were machined oversized and bushed to put the oil passage in the proper spot.

I was just thinking of this truck the other day and it's status. whether you swap the engine out or not, it needs to be sorted out for educational purposes.

That's the cleanest Commanche I've ever seen 🙉

Dex pull your rockers off and put a straight edge across the top of the valve stems. I think your going to find some are higher then the rest. This happens when the valves are not machined evenly. With non adjustable rockers and hydraulic cam you will have some valves hang open if they are deeper (taller) then the rest. Use a feeler gauge. I’ve seen this before. Hope this helps

I love your channel and attitude! Thank you for being honest in your videos. There are too many out there that are nothing but commercials and ego trips! You will get it figured out! We had a saying in my old line of work "if a man built it, a man can fix it!" Lets follow the oil( I know you have) Oil feeds from the pump to the long galley. It feeds the lifters and the bearings from that galley. If the lifter bores are tight and the bearing specs also tight, the lifters might be getting more oil than they can handle. They can only exhaust a certain amount into the pushrod.They are metered. Cylinders 1 and 6 are at the dead end of the passages so in my very humble opinion they will suffer most. I wish you could have gotten all the bearing clearances cam, crank and rods as well as the lifter bore measurements. It would be interesting to see them all written down. Thanks and keep up what you are doing! Jeff

LOVE This series! this is a head scratcher here

Thank you for your time man!

What if it’s got a big lumpy cam or the cam was not ground correctly? I’d throw a known good stock cam in it and see how it reacts.

You are awesome. Thank you for the update dex. I’ve been asking and you answered👍👍

Love your dedication to solving the problem! Hope this is in your rear view mirror very soon and hope it is worth the time it is taking.

You are so very determined. I admire that

Ok Dex look up Rhodes lifters they used these back in the 60s and 70s . They are the first Variable Timing Flat tappet Lifters . Old schools builders used these when installing a radical cam. At idle they would bleed off internal pressure and basically shorten the lift of the cam . When you ran the motor above 2000 rpm or so they would pump up fully there by increasing the lift. Yea I was one of the guys hollering deck height but you are definitely onto something here. Also the Cam , here on RU-vid there is a channel, Delta Cams , they do camshaft grinding, actually they take old camshafts and regrind them. After watching your video this time it definitely puts me in mind of a improperly ground camshaft. Just my opinion, hopefully you will get this figured out, bunch of us are waiting with anticipation. Good Luck Fren õ.⁷

I like your willingness to admit what you don't know, and you have a good understanding of what's going to hold interest and what might as well be skipped over in editing

I'm pretty sure your dad KNEW you could change the head gasket correctly and was able to get you to do it for $50 instead of paying a shop!! LOL. Love your videos, keep it up!

Happy New Year, brother. I applaud your dedication and commitment. I would have given up on it a long time ago. You will either figure it out or change it out. You will get it running right. Stay safe.

Glad I found you again Dex!! I have 3 XJ’s I’m trying to restore. Your a huge help man!! Good work.

Love your format. The scattered thoughts are awesome I am glad I am not alone. Keep up the good work I am an XJ guy myself

Soon as you upload This guy is watching , love xj’s

Hey man much respect for going this deep into it! It can be so frustrating to get hung up on a gremlin you cant hunt down. Love the videos thanks for the very detailed one! I like your long form content!

Appreciate the dedication to the brainstorm. If it runs right with no oil pressure and runs like shit with it...the lifters cant get rid of the oil. Something is preventing the oil from coming out of the lifter, theres a blockage somewhere

Dex I just want to cry for you. You've worked so hard on this engine. I pray you figure it out. I'll say the p word because it definitely helps. God bless and be well Brother.

My guess is something with cam, cam bearings like you said or something in the oil valleys blocking oil. Love watching these videos, hope you figure it out.

This engine is super interesting. On the last episode about it I thought it had to be the cam but the slowed oil drain makes me rethink that theory. I can’t wait to find out what it is

From what I have seen in this video, two things need to be done: 1) set proper lifter pre load by shimming the rocker arm pedestals, 2) check/set rocker arm geometry by measuring and/or adjusting pushrod length. These are all standard procedures that need to be done when heads and blocks have been resurfaced, and head gaskets are non-original compressed thickness. If you dont have a service manual on hand for the 4.0L, get one, and study it. Hope this helps. Dont get discouraged, because learning only takes place when mistakes are made.

Man, you're the jeep guy. I'm on the hunt for my first xj. I love the body style. Like the early 90's. I have an 87 samurai and a 2000 f150. But I'm wanting an xj and a 79 f150. Good stuff man.

Owning a Jeep has made me really appreciate & miss my Toyota

Great video, thanks for sharing. Hope you get to the bottom of it.

Dex, you are awesome. I just can't believe you haven't figured it out. I think you will. Looking forward to the next video ❤

What about the cam? Did you verify it's the right cam for that engine and that the base lobe isn't too large making the lifters sit too far up and not letting oil push past them?

Dex, Have you checked cam: crank timing? You should be able to see at what degree the valve begins to open. The wet plug, cold run suggest you either are not firing or firing on the wrong stroke. Almost like a timing chain off a tooth with the computer trying to correct for it. Change the lifters, then change the cam. Only other thing would be lifter bore. Somehow the lifter is creating oil pressure when it "pumps". It probably acts like a solid lifter while also being a compression pump for the oil. Are there seals in the lifters allowing blowby when the lifter cylinder is compressed but not when the piston is maxed out? Fun one, gotta love these ones. Black exhaust, unburnt fuel possibly oil leakage. " Compression in the intake? Raw fuel mixed in, backfire. Exaust in the intake especially from an unfired/dryfired cylinder, not so much raw fuel but addittional heat within the intake? So if i understand correctly the oil pump is driven by the engine rpm to deliver quantity more than pressure relative to motor speed. The pressure should remain fairly constant over the rpm band. Oil is pumped through galleys into the lifter bore where slots in the lifter housing allow oil to pass above the lifter? Or into the bottom of the lifter? The oil forms hydraulic pressure to push the push rod while simeltaneaously allowing the oil to dampen the motion by creating an outlet for the oil through the lifter and up through the push rod to the valve train. But somehow the oil is not passing through the lifters and push rods. The lifters themselves with no outlet for the oil will become pressurized and could act as little compressures feeding oil pressure back through the galley's. Can you check pressure from the pump vs back into the pump? Something between the oil going into the lifters and how it gets back out isnt working. You end up with solid lifters tightened all the way down. I dont really understand how the lifters exactly work but the hydraulic part of hydraulic lifter will follow basic principles. What i recall is a valve body and pistion assembly. The push rod activating the release for the pressurized oil to maintain more than just spring force. The oil will need to be sucked in or pumped in with minimal pressure and released at a controlled pressure. I didnt understand from the video how this lifter accomplished the hydraulic valving to maintain constant pressure. Did someone put solid push rods in? Ok now I'm following more here. The resistance of the oil being pushed out of the cylinder around the piston is a precision gap allowing for "float" but designed to maintain a constant proportional pressure to balance valve spring resistance. Your oil pressure is equalizing to overcome valve spring pressure. High crankcase pressure or no? This will be interesting to follow. Gotta love those jeep gremlins.

This is just pure Jeep gold, and always is. Plain and Simple.

Man oh man! I admire the dedication poured into this issue. I’ve watched both episodes by now. Have the valve spring rates been checked? Seat pressure- open pressure. If you have 40- 50 pounds of seat pressure that could allow the lifter to over come the valve spring allowing the lifter to pump up and hold the valve open. I know it’s two different heads. Don’t know anything about what was done to the valve spring set ups on either. I’d say you’d want to see at least 75-80 lbs on the seat. 170-200 open for stock but that’s just off the top of my head. I’m sure Justin has some specs. May try shimming the springs if you guys don’t have access to a valve spring tester. This is the only thing I can think to help alleviate the situation.

Mannnn you shimmed every valve yooo that’s so awesome man you are a legend

What a conundrum. I think most folks would have given up by now! Way to keep at it! I wonder if oil viscosity is exacerbating the issue? Changing to a lower viscosity will probably just mask the problem though and have never heard of that really affecting lifter performance, only lifter noise. It's almost like the oil isn't escaping the lifter correctly and I believe you already replaced the lifter on the front cylinder? If not, maybe the check valve spring isn't right? Good luck, Dex! We are all pulling for you!

Dex you have lifter pump up keeping the valves open . What really bothers me is that it ran good on your engine stand but went back running bad when you reinstalled it. What changed? Anything on the truck oil related that wasn't used on the stand? ( Filter adapter , distributer/oil pump drive, ECT. I retired 5 years ago from 45 years of mechanics and I feel like I'm reliving your nightmare 😂 . Good luck I really hope you figured it out and you share it with us . Definitely a new new one for me.

You got my respect! Suggestion... adjust rockers while it's running to get best vacuum. I think you have them too tight and the low vacuum is tricking the map sensor thinking the engine is at wide open throttle. This will make it run rich. Hope I helped out.

The valve spring could be weak or valve guide sticking, valve grinding and seating process done incorrectly, push rod length, but I agree with you on those, something going on with the guide itself letting the valve rock to the side when ya put the smallest tension on it, staying strait and sealing with them loose.

You should try getting in touch with Ivan from Pine Hollow Auto Diagnostic. This seems like something he might be very interested in. I personally think it has something to do with oil pressure not bleeding off from the lifters like it should, but I can't think of what would cause that.

whew this is a good one, i think it’s great your grinding through this. I think you have mentioned you changed lifters but I don’t remember you saying you have switched camshaft. If you haven’t I feel like you need to rule that out too. Or measure the base circle very meticulously against a known good camshaft. I think your theory is right to much oil psi in those lifters… but why and how could you test it. maybe you could figure out how to trace the circuit for those lifters and make sure nothing is in the passage effecting psi on those lifters only. looking forward to more episodes on this.

Just to rule them out, see if you have some shorter pushrods that will work, at least a couple for #1 cylinder. Your brother should have a bunch to choose from. Also, on some pushrods The tips are pressed in. you can shorten them by taking the tip off, shorten/ cut rod and reinstalling the tip. *Just for testing. Also there is major cam manufacturer that will make up a set of custom pushrods if you give them the measurements usually expedite a set if needed. Even if everything tells you not pushrods if you quickly eliminate them as an issue it may help the final diagnosis. As others have said, check oil flow through push rods & rocker arms. Love your style Dex,don't change a thing ...okay just one thing slow down a little when explaining important stuff. :)

love the dedication please build this guy a new engine or just swap it.. Fantastic work dex

@justdexit I showed this to my dad whos been a mechanic longer than you and I have been alive, and this is what he said. #1 compression test # 2 vacuum test # 3 verify cam to crank timing #4 smoke test, remove spark plugs, and remove rockers, looking for cracks, will see smoke from spark plug holes if there is an internal issue

I had this exact same issue a few years ago. Drove me crazy along with 2 dealerships. Try changing the throttle body and see if that makes a difference. I know it sounds crazy but after everything you've tried they all told me it couldn't be the throttle body but that's exactly what it was that fixed it on mine.

I had a set of lifters from china and they didn’t work for me it did the same thing this jeep is doing they drill the lifter pressure circuit to high up and cause a whole lot of head aches along with not tapering the top to bleed off the pressure better

sounds like a bad camshaft to me

As you shim the rockers you are delaying the point the valve opens. So if the valve opening a little later gets more compression the cam must be ground or timed incorrectly. Was the cam the original to this engine or a replacement. Also the drive sprocket/gear was not a press fit is that normal. As you said the 1st and 6th cylinders are reacting the worst due to for lack of any other word harmonics. The air charge is partially being sucked out instead of sucked in. Try measuring the amount of degrees,with a degree wheel, when the intake opens vs. a known good engine. The same with the exhaust valve. You could try to figure which is off by shimming only intake or only exhaust. The one that gets compression back is the one ground wrong. My money is on the cam or sprocket/gear that is wrong. As you are aware aftermarket parts are not always good. If it’s not one of of these I’ll send $25 to the Dex fund Ron

Try swapping the camshaft for a known good one out of a running engine . The spec on the cam may be just a little different .. Or even the wrong cam all together . I always thought that the hydraulic lifter filled making it solid with just a little give .and the pushrod rode on the top of the plunger (at full fill ) and not anywhere in the "squish " of the lifter ... . If you have to shim the rockers 1/16" .. Try push rods 1/16" shorter than what you have and see if it runs right ... To me its looking like the pushrods are too long for the camshaft grind .

lots of people talking about timing. Loosening the the rockers is opening the valves a little slower/later almost like changing the timing, and it seems to correct your problem. If the distributor was dissembled to be cleaned (before you touched the truck) and the distributor gear was reinstalled on the distributor shaft 180 degrees out... the timing will be off ( i think its about 11 degrees, i cant remember) but it will still run (the computer will adjust for it) At least some of the newer coil pack models will disassemble

You could do a dynamic compression test “running compression test”. Loosen or tighten the rocker as it’s running to see the pumping loss/gain.

Here is my 2 cents , oil cavitation in the lifter bore causing a oil imbalance on any lifter you throw at it causing the pistons in the lifters to collapse or not let pressure out . In theory the heat of the oil can change its “cavitation rate if that’s a thing “ It could be a slag of metal in a oil journal creating turbulence or a void in pressure for the lifter. I’ve seen this in a Harley oil pump once it came from the factory like that it wiped the crank out . “ Harley wouldn’t own it either “ I’m with you on this man I’m thinking WAY OUT OF THE BOX on this. Hang in there God bless and mechanics unite lol.

They used to thin a oil during the break in period, or skipped it all together. The break in is actually for the seals while all the new parts are still sharp edged. Put the new oil pump back on and throw some thick oil in it. That's why the lower oil pump was working a lil bit better, the oil that's in it is to thin and still has grease in it. Good video! And good luck

It sounds like you're on the right track. It makes better compression when you loosen up the rockers. I don't know the whole history, but is it possible to just buy or acquire lock-nuts for the rocker studs and just set the lash like most other hydraulic lifters. Ex: 0 lash and then add half a turn on the nut. Hope this helps.

I had a similar problem with an 80s gmc suburban. Turned out to be a bad distributor. The magnet inside was weak. Truck wouldn't idle. Replaced the distributor and it ran like a dream.

Valve springs ! valve springs ! Valve springs!

Oh man I feel your pain. I spent 3 weeks trying to fix a multiple cylinder misfire. I lost hours of sleep on it.

I think that oil galley after lifter is clogged up causing too high pressure at lifter topping it out. Try putting 5w30 in it. If it doesn’t help, cut first and last cylinder and call it 2.5 liter (don’t forget to change stickers) ;)

This is gonna sound dumb. Could a pushrod have an obstruction blocking the passage? I love your channel!

Timing is off somewhere bottom line. Check distributor. If correct. Check belt / chain. It’s off by a few teeth

Do they only make one cam for that ? I am leaning towards the cam not being the correct cam for that. I believe by losing the rockers you are changing valve timing and lift.

Wrong length valve stems?

I know this is a lot but you are going to have to pull motor again and get the mic tool out and check against good parts it's right in front of you but you just can not see it with naked eye ..

I think you are on to something with the oils pressure issue. It runs fine after the pressure bleeds off but after it builds pressure you have valves stuck open. Something is blocking the oil passages. Oil passage plugs in the block installed too far in? Wrong depth of plugs? Oil pump too high pressure?

Awesome man!!!! Smart guy love your knowledge thank you. This is interesting. Could oil viscosity be a issue???

If you can see a difference in the two cams with your eyes something is up .Right? there is not that big of difference in two stock cams . Right? Ether something is up with the cam or you have a recurring problem ( lifters maybe) remember inspect don't expect!!! (Measure the cam damn cam lol !!!!!) I sure hope you get it soon . I don't see how you can work without being paid I'm praying for you!

you cannot compress a liquid. once the oil is the lifter, it will not fluctuate. it will push the piston of the lifter to the top. Im still leaning towards something being out of spec. cam having a higher lift shouldnt do that, cause like you said its the back side of the lobe. but if its a wrong geind from the begining possible. but again im leaning towards the block, would have more piston protusion tho. did that seem off??

Geeeze, just watching all the trying without desired results almost makes me cry. 😔😔

Man I feel your pain 🤦🏼😵‍💫.

This is the same thing that caused me to quit a job I loved. Rebuilt engines by other people to save money. After the 4th one, self destructed . I HAD ENOUGH. I got paid but I had no control on quality and besides the insult of my time not being worth the few more bucks I just had enough.

That's why I like solid lifters one less thing to worry about.

I have a question when you had it torn down did you check the centerline and overlap on the cam just a thought but maybe the cam has a weird grind on it to try and bleed off compression because of how much they took off the head and block only way to know for sure would to be to swap the cam even if it's with a know good used one I have also seen cam profiles that push the lifter up too high in the bore for the oil groove to bleed off pressure and a groove has to be added to the lifter to aid bleed off.

Have u tried a larger copper head gasket to put the deck height back to normal. Could also try an adjustable rocker arm so u can set to the height needed to seal the way it is

Head or decked is warped. The fact that 1&6 are giving you trouble basically verifies that. If the head was out of tolerance when the valve job was done that would only amplify the problem

Weak value springs, would me my best guess. Unknown cam, block, could be a weird after market cam that needs a stronger value springs.

If it's the front and rear cylinders only it's got to be timing related or cam related. Providing the lifters are correct and functioning. And if the timing is right then the cam loabs aren't and you'll have to get custom length push rods. The valves are obviously opening before all the fuel is burned

I hope you don't just leave us hanging??? You're incredibly smart I know you can figure this out 👍

Stuck fuel injector wide open…

Weak valve springs. You were on the right path when you had to shim the rocker stands. In order for hydraulic lifters to function correctly, they have to push against a determined force otherwise they "pump up" and act like solid lifters. With weak valve springs there is not enough resistance for the internal parts of the hydraulic lifter to assume a mid point in their design range so they expand to their full length and function like a solid lifter. Without your shims under your rockers, the valves weren't closing completely since the lifters were pumped up to their full length which is why you had low compression. With the low compression in your cylinders the fuel injectors were spraying the same amount of fuel which caused a severely rich mixture. The injectors didn't realize there was less combustion air and sprayed the same amount but was too much for the reduction in air. You can easily check the valve spring tension without having to disassemble the head by removing the springs themselves from the cylinder head.

I worked on 1000 xj s ,I currently own a rhd xj and 2 wj s .I think the after they cut the seats of the valve and cut the valves.youvalve height is more taller letting the valve stay open too long .have the valves grinded on the to of springs .. I worked for jeep masters in Austin Texas 17 years Good luck you getter done

Do you know any fixes or rigging to make the zj dimmer slider to actually work and not flickering

Not checking previous comments but if that's a renix the REM may assist diagnosis

Shot in the dark , ratio of the rocker arms all the same . I’ve seem intake and exhaust rockers having different ratios. Just a thought.

I believe in you

Hey Dex great video i just want to say I enjoy the longer videos so you know but I was thinking you know how blocks like Chevy small blocks and big blocks will distort with just simply pushing on them and you can see the cylinder bore indicator drop. Well I’m wondering if this block is distorting in a way either due to poor manufacturing or just weakening with time that it is causing the oil to keep pressure in the lifter and hold the lifter up I don’t honestly know how good of a thought that is or if it may even be logical but just a thought I had. Trying to follow everything you’ve tested has been a feat of its own but really enjoy the videos. Hope you figure this out would really like to see the outcome.

I think you got some valves slightly open I would take an old compression tester and cut it off hook an air hose to it pump air into the cylinders Make sure both valves are shut and take the oil cap off so if you have air coming out of the throttle body it's an intake valve problem if you have air coming out the exhaust it's an exhaust valve problem and if you have air coming out of the oil cap then got ring problems

Could weak or the wrong valve springs cause this? I don't know what would make this happen but thinking maybe it's not pushing against the rocker hard enough to push back onto the lifter allowing the lifter to pump up more that normal. Also, not closing the valve all the way while running.

the only thing I can think on yours is Cracked block in oil passage. Run o weight oil and change to 15-40

I had a similar problem with my XJ and I rebuilt the motor and everything and nothing changed, I had some old guy argue with me for days saying it was an O2 sensor, I finally threw new ones at it and it ran like a dream after. Not saying that’s your issue but I don’t think it would hurt to try. And it’s important to note I never had a code for an O2 sensor either

I have been in these positions before just remember a lesser man would have already gave up you will figure it out its definitely making a good video series btw try a new oil filter

I had tge same problem on a 4.0. Very long story short and lots of parts later it wound up being a bad lifter. It would stick all the way open and hang the valve open causing a miss. I suspect you have a few seized lifters. I got lucky and a little seafoam in the oil freed mine up. If you have more than one might be better to replace them all. Just because the lifters are new doesnt mean they are good.

Valves or cam lobes!

Have you checked valve stem length on the affected cylinders and compared it with the good cylinders?

It sounded good on the stand, Is why I said throttel position sensor in the truck

I have to ask since it’s a Renix motor- did the machine shop monkey with the oil filter adapter parts and (1) get something wrong or (2) use a filter adapter kit to change it from the original oddball metric filter to the later 3/4 x16 (and screw that up) creating a problem? I’ll study on a 4.0 oiling system diagram since I’m relatively new to them, but SBC has a ball in the rear China wall that has to be set just right to direct oiling properly and some shops can’t seem to get those right. If the 4.0 has something similar the shop could have gotten that a little off and made a block with an oil return restriction by accident, leaving the lifter gallery constantly over-pressurized like you said, especially at both ends of it at #1 and #6.

My dad had that issue, but his problem was the harness to the computer, and he had to tie it down with zip ties, and it stopped the shake . I believe it was probably the computer soldering needed to be re solder

That’s it brother, a bug bump on cam.😂

If I was the owner of this Jeep, I cut my losses and have you do an engine swap. Take this engine and leave it at the door of the “engine builder” and TRY not to let the engine fall through his door 😉 if you know what I mean.

Check the valve spring tensile strength . Or put performance valve springs in it

Could be the valve stems are to long now that the head has been shaved and the valve stems have not been ground down to match so now the valves are not seating properly beings it's hydraulic lifter and that's why when you shim the lifter it runs good. Both of the valves are staying open, try putting a whole different head on it and see if that helps, or pull the head and make sure both valves are seating properly. Hope that helps you, and awesome content man

Curious was a new Camshaft installed? Wonder if it is a flawed Camshaft where some of the lobes were cut in the wrong spot, also has base timing been checked?

I skipped some of the video because it was too painful to watch so please excuse if I missed something. When the engine ran fine on the stand you checked the oil pressure but in the vehicle you did not check the oil pressure. After seeing this unfold I find myself asking, "Is this guy so clever he acts like an idiot to get more comments? Because how could a man who foolishly wastes his time acquire all those tools, unless he inherited a fortune?" Anyway interesting content and I've fallen in love with the XJ enough that I have bought 3 since Dec 23rd. I've been watching your content for a couple months.