The Ultimate Guide To Identifying Jeep 4.0 Heads And Spotting Common Problems! 

Let Justin talk. I wouldn’t mind if the video was 1 hour long. It would just keep me from having to dig through all your videos to find one I haven’t watched 😂

I plan to try and rebuild my 4.0 in the next month or so, so im trying to absorb as much info as possible! Thank you for all your helpful videos!

My 05 4.0 had 300k+ on original head. Matter of fact the only thing I did replace on that engine was 1 alternator, maybe 5 water pumps and 3 radiators. It'd been over heated more times than I'd like to admit. One time it got so hot it was only running on a couple cylinders by time I got off the highway and the thing still ran like a top. Another time the rad tank ruptured and exploded coolant all over the car ahead of me in the drive thru 😂 It was a good jeep. Barely had any issues with it besides rebuilding the front end a couple times and the usual frame rail rot. Considering I put 300k miles on it from new I think that's pretty good

Thank you, thank you, thank you! I asked you to do video about this and here we are. 👍🏼😎

This is a life time of info. Thanks for taking the time to video all of this Keep with long, short and mid length videos they are all good! Also your not a HACK you make things work big difference. WELL DONE.

Best Jeep channel on the internet! Thanks!

Now I really want to see you daily a cracked head. Great video

Can you go through the ls valves and springs on your stroker head? I’m very interested that’s really cool I have a whole bunch of gen 3 valves and want to do that on a jeep engine

Might need a head right now so thanks for the help ,

i like Justin , he should teach more often imo :) good chewin da cud guys ty . your cool to Dex lol

I’m here for it. We’re talking about core engine stuff in 101 before engine class 103 next. 102 is electronics and happens after 103 for me.

Ever run into different length push rods? Put a tuppy head on a 98 block after fighting low compression and finding bent valves for no apparent reason, put a tuppy on and got better but when rockers were tight valves were open, loose they had better compression

Good stuff, Keep the videos coming guys!.

Very interesting guys.

Typically most people would have two or three engines to look at side by side. So when they see a common issue with two or three engines. They will make a generalized statement that all of a similar type engine will have that same issue or will not have an issue. Making a statement based on a small sample my not be true. Dex, you and Justin have literally hundreds of engines to sample and from that you "can" make a generalized statement. Also the year comparison of heads was very interesting. Do more comparison and parts interchangeable vids. Thanks.

I have a 91,92, 94 xj and from my experience on valve seals when buying seals the 94 doesn't list as a fit on the 91,92. all three are 7120 heads. although I think they would fit just fine I went with what was the recommended fit. I personally like the positive lock type. and one other thing I found interesting is cam lift , rocker arm ratio is 1.5 not 1.6 on the older heads. look up melling camshaft specs. and see for yourself

You have put my mind at ease. Thank you guys.

great video guys! thanks

Thank you for answering the head issue's. Please talk about blocks next please

Fascinating information 👍

Imma check tomorrow, butI just think i cracked my head today 😅 hopefully its just the gasket but i hear a hissing in the back of the 4.0. Thank you in advance

You have accumulated a lot of knowledge the 'hard way' but you don''t forget as fast that way. I have 7 WJ's - one has a 4.7 which is a big PIA to R&R, any secrets you'd like to pass along ? Keeping my TUPY's and using 0331's only when necessary. I have an XJ but I have to remember the incompatibity issues. Hope you can stay on the money makers and sell the extra parts you gather as you go. Nice to have a machine shop nearby 🙂

You guys have me freakin out now 😂 should take my head off to check for cracks

I dont have a jeep...anymore. first vehicle was a clean 83 cj7. Wish i never sold it. Anyways... i just pulled the head off my 22r. (Low compression on #4)... and about to pull a head on a free new holland 4630 that got so hot i had to pull the pan to get the oil out. Im sure its cracked... its gotta be. Only a 3cyl but im sure its cracked. Ill find out in a few weeks when i pull it. Love the videos man!!!!!

The burnt valves was interesting. Didn't know that. You can keep the video long as you can

renix motors also have a different cam profile - partly why they have less power

You guys have the inventory of used heads to choose from, what about the average jeep owner? Do you suggest they go to the scrap yard and try to pull heads, or purchase an aftermarket head and try not to overheat it?

This is why I firmly believe the 98 XJ is the best year XJ. 99-01 had the smaller ported head. 97 had air bag issues, 96 below doesnt have air bags. I put in every factory option "Limited/Classic" can have in my 98 so I dont see a reason to get one without a good BCM or engine head. Why I'm saving my rusted 98.

I did not hear you mention it, but when they went from Renix to the HO head they also moved the intake port higher up on the head to allow for better flow. If you look at the two heads at about 2:36 of the video you can see the Renix intake bottom edge is about even with the exhaust and the HO is higher up on the head.

So that 45 digit number that's by cylinder 3 I believe there's a RU-vid video it tells you certain numbers are more prominent to crack than other numbers.

Well, I have a 2002 WJ with the 4.0, that I bought from some folks that definitely overheated it, then it did it again on me once, as the fan control relay has gone-out twice. Between a shop and myself, the motor ended-up getting new pistons (shattered #4 and cracks in 3 of the others)/rings, rod bearings, head, intake/exhaust manifold, valve cover & oil pan gaskets, rocker arms/pivots & valve springs, with pushrods and a new fully-welded aluminum radiator. The shop swore the head wasn't warped or cracked, but after watching this video, well............... 😐

I need to know more about those LS valves n springs

Sooooo , you have a LOT of what you consider Junk Heads ,so can tje Cracked seats be fixed reasonably "ie" machine the seats out and replace them ??? Then weld the other cracks up just thinkin out load , we have welded rare tractor heads before !!! I'm just thinkin Heads are gonna start gettin harder to find , if yer just throwing them in the Iron pile for scrap, it might be worth a shot just to see if it's possible to save a few ??? Might not be economically feasible ???

The wj engines with the two exhaust manifolds are those manifolds prone to cracking also? I have a loud ticking noise on the driver's side and while listening with a stethoscope the ticking is coming from the exhaust.

Would a 0630 or 7120 be a viable performance upgrade for a renix engine? Im finally getting my dream vehicle, the 89 Comanche!

15:00 the re...what? Oh you had an X at the end...ok lol

I’m deep steeped in SBC but new to the 4.0. I heard that in 96 rhe 0630 with the new valve cover and gasket won’t interchange with the 7120 or Renix gasket and cover. Same with the 0331 that followed it. True or not?

Great video. Do you have knowledge or an opinion on the aftermarket aluminum 4.0 head available?

Heat,..kills Electronics also. Thanks

So for 4.0s, what is considered to hot? Anything over 210 ?

Any opinions on the Edelbrock aluminum heads?

Dex I need the fuse box located in the passenger compartment on the driver side because mine are corroded and the fuses pop out when I'm driving sometimes my blinkers don't work can you sell me one. I have 87 xj Renix . Would Edelbrock Aluminum head work on a Renix 4.0 ?

I have a question I hydro locked my 94 4.0 xj a week ago and now one of the lifters doesn’t sound like it’s building up a lot of pressure I didn’t bend a rod or a valve. Think I need to rebuild ? Or is there something I can do? I’m getting 40-45 psi of oil pressure when idling

👍👍

just got my first zj for a trail rig it been sittin bc of a tcase but runs so good and smooth any tips to keep it cool i should know ? i wanna avoid getting it hot at all means

Can you put valve seats in a 4.0 inline head ?

0:54 is that the rc jeep?

I have a 05 wrangler automatic, need a trans and wiring loom And computer! Help!

Hey Dex do you have a trail ready jeep for sell? Let me know I’m not very far from ya and I’m looking for a new toy for me and my family.

Where are yall located for purchasing parts?

Do u guys sale used parts looking for a head for a 96 jeep xj

Where can I get tupy head for 01 cherokee?

Can you put a 2005 tupy head on a 1993 4.0l block

The 4.0 was a very torquey engine but they sure had too many issues that should’ve been addressed.

I always thought the high output was primarily the fuel system.

Someone already put chevy ls heads on a 4.0