7120 head conversion...

Well, it seems after some more digging and Jeep build progress, I have the opportunity to upgrade the head on my Jeep. I have the engine halfway to a head gasket change with all the upgrades I am doing, and figure I am this close, I might as well go a head and change the gasket, and since the old head will be off, go a head and replace it with a newer one. This actually makes things a TON easier with my intake and exhaust upgrades too, which are already thought out and good to go.

Pertinent info: starting with an 88 4.0 rig, and needing a donor 91-95 4.0 head with #7120 casting.

So here is the dilemma though, for the donor head I have 2 options:

- Option 1: I found a local one for $60, for just the head and valves, no rocker arms, push rods, or the caps, pivots and bolts for the rocker arms. Also no valve cover, so I am left to either re-use what I have now (old and possibly non-useable) or replace it with all new stuff, exception being the valve cover, I am pretty sure mine will work. It is less than 100k, and looks to be pretty clean as it sits, and looks pretty good actually, and I know it came off a good running motor.

- Option 2: I called around to some local yards and found one at a you-pull for the same price, $60 complete, so I know from that I can get all those other parts and re-use them, except for maybe the push rods, if not too expensive I might just replace them since that is the only "between block and head" part that is not staying with it's original engine. I also know they will probably let me take the valve cover with it, and the thermostat housing without issue, and all the other bolts that go to this "new" setup. The ONLY downsides here, all I will know about the donor rig is what is written on the windshield, and the odometer, and I DO run the risk of finding the head cracked or damaged once I get it off, or other components therefore wasting my time, and possibly money if I find out later. Then of course taking the time to do all this more than likely by myself (most of my friends are unable to help with something like this) so it may take a while...

Any ideas on which option would be better here?

And one more question, as for head bolts, I am more than likely going to replace them as cost isn't TOO bad and since I don't know this history of the donor rigs (assuming I trust the PO did the paint thing if they re-used them) and my rig is 24 years old (assuming everything is factory still) and has quite a few miles, should I get a set of Renix head bolts, or the head bolts corresponding to whatever donor rig I get the head from?


Thanks greatly in advance for any help you can provide, hoping to get these parts by this weekend so I can start putting my engine back together...

Paint

Renix head bolts will be fine and they may be the same as the HO bolts anyway. Use your valve cover and CCV system off the 88.

cruiser54 said:

Renix head bolts will be fine and they may be the same as the HO bolts anyway. Use your valve cover and CCV system off the 88.

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I know they are different, but I just don't know if it is the ends, or the threads or what that is different about them. Also, the Renix ones are a pain in the ass to find it seems... MAY have to special order them, and I REALLY don't want to have to do that... I was planning to use the cover and those two lines too, unless there is something about Option 2s' cover that is nicer than mine lol. At this point, and after looking up prices last night for all the valvetrain parts I would need for option 1, I think Option 2 would be my best bet right now, then just go ahead and do the pushrods. Then my only real expense aside from the cost of the head will be the head gasket, head bolts, pushrods and maybe the valve cover gasket... Hoping I can do this as cheap as possible.

In the future I would like to go through the whole engine at some point, but for now I am just doing this, finally hit a wall where I can say NOTHING BEYOND THIS POINT! Of course this project originally this thing was just supposed to be a "learn how to fix and rebuild it so I have a stock vehicle that is my own" And has since morphed into something with ~5"lift, 33's, axle swaps, regearing, trans swap, HD floors and rockers. Performance shocks, clutch and clutch hydraulics, intake, exhaust and brakes, custom bumpers and even a 12k winch... On the plus side, it is kind of nice to finally have a reason to say "nothing beyond this point" lol. Oh, not to mention, doing the YJ bracket swap for the alternator and eliminating the mechanical fan too... Still a VERY small chance that won't happen immediately, but again "since I'm in there, might as well"... Thanks for the info,

Paint

I did two swaps Renix to HO. Used 7120 head on a Renix with Renix headbolts.

Any idea if later bolts are compatible? Having a hell of a time finding Renix bolts locally and I really don't want to have to special order them... Or have any idea if either head bolts (assuming donor's aren't marked) could safely be re-used? I have had a couple people tell me they have re-used head bolts multiple times, but I REALLY don't want to if I don't have to...

Paint

I never noticed a difference in them. Swapped head on an 88 Renix block to 7120 and the bolts were the same.

One writeup I had found said something about a difference, I guess they were wrong lol. Going to the yard tomorrow, will just grab the bolts anyways I suppose and evaluate when I get home, maybe I can get away with re-useing them. Though still think I will just replace. Looking thus far like I will be spending $60 on the head, $25-35 for the head gasket and $40 for new bolts if both sets of mine are a no go. Then possibly a valve cover gasket. Hoping there are no broken rocker arms or anything in that area so not factoring that cost in right now...

Seems pretty easy to do the whole thing. Never done anything like this before with an engine, but it will make all the intake and exhaust stuff I was already planning a TON easier, plus whatever power and mileage gains I get out of it too... I mainly just want to make sure I get EVERYTHING I need from the yard so I don't have to go back once I get started. Can take my time pulling my old one off, but really need to make sure I get all I need there tomorrow. Really hoping that I don't get a cracked head or anything like that, or at least hope I find it before I leave... Thanks again,

Paint

I think the real late headbolts had different heads on them.

You'll be fine. I wouldn't even waste the $40 on new headbolts if you're tight on cash.

Maybe that is what I was thinking then...

Only thing to decide now is which set to use lol. I got a call from another yard today as to what they found for Jeeps in the back. I had to call back to get the years (the guy had just stepped out for lunch who looked) when I had called the first time. And they had a 92 XJ and a 93 ZJ. with a 4.0. Asked if he could still do $60 for it as we had discussed yesterday, if I of course pulled it and he said "I'll tell you what, you come and get it today and pull it all yourself, I'll do $50 so I don't have to pull it". Needless to say, my response was "I'm on my way!"

Went there and the XJ's was half pulled. I wanted to make sure I had all the bolts, so went with the ZJ for the donor. It had a few more miles than I would have liked but 1: It's a 4.0, and 2: It was $50 for EVERYTHING!. Got the head and all the rockers, bridges pivots and their bolts, valve cover and its bolts and air fittings on top, head bolts, pushrods and a bunch of other misc bolts. Took me about 2 hours or so to pull it all as all my research into pulling this thing was for XJ's so kind of had to adapt on the ply a bit lol.

The ONLY 2 problems I seem to have run into, a few of the water jackets opened up (I admit, I kinda did a couple of them [tried to scrape off the "gunk"] before I knew what they were...) Which seems easy enough to fix by some of the writeups I have come across thus far (the packing peanuts and pig putty thing); and the second thing being, and I have NO CLUE how the hell I missed this till I got home, but the 2 outer exhaust manifold bolts snapped off a bit in the head... I DO have some power extractors and easy outs and such, so I hope I don't have any issues getting those out... Comparing one of the broken bolts to the pulled ones I have from my current rig, there are only like 6 or so threads in the head still, bolt broke right after the non threaded are of the bolt.

Other than that, aside from a ton of grease, and a tiny amount of rust everything seems fine. No major flaws of any sort that I can see in the rocker arms or anything of that sort. Small amount of rust in 2 of the combustion chambers, but it looks like it will all wipe out pretty easily... So now that I have all the donor parts, it brings up a few more questions:

1. As far as pushrods go, assuming both my sets are good, should I use the ones from the Renix, the HO rods or just get new ones?

2. Assuming I do re-use the head bolts, same thing, Renix bolts or the HO bolts? It doesn't look like the HO ones have paint or markings that they have been used, and I haven't actually checked mine yet to see. The only thing I could really see coming up, I have been working on this Jeep under the assumption that everything is still stock. Under that assumption the Renix bolts are older, but the HO bolts have a few more miles than my Renix...

It looks like my Renix thermostat housing should fit without issue on the HO head, so I don't have to move the coolant sensor, just that sensor on the top drivers side back of the head. Got the head and everything but the bolts and pushrods soaking in a combo of diluted purple power, and simple green right now, going to leave that through tomorrow then power wash it to clean it as best as I can Sunday.

Looks like as long as I can re-use the parts I have, will just need plugs, head gasket and fluids and I am good to go Really hoping this thing cleans up easily (and I can extract those bolts easily) so I can get the engine back together in the next few days... Will be able to get back to the body work then finally...

Thanks again for the help, I do really appreciate it.

Paint

Use what you want. It all interchanges anyway. What's this stuff about packing peanuts?

cruiser54 said:

Use what you want. It all interchanges anyway. What's this stuff about packing peanuts?

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I am just a bit worried about wear patterns on the pushrods between the cam and rocker arms... both renix and donor are in about the 230k range... Probably will go with the HOs since they are newer though, assuming they check out as straight that is... As for bolts, will probably just re-use whatever looks to be the cleanest, which already seems to be the donor bolts, and they are newer too...

The peanuts thing is basically put a packing peanut in the jacket hole leaving about a 1/4" gap to the bottom of the head, then fill it in with JB weld, or something similar (I have "Pig Putty" for example) then sand/file it flush with the head and they are good to go. The peanut dissolves so no worries there...

Paint

Why?

Was worried there would be a wear pattern from the Renix pushrods on its cam shaft and using those pushrods on the HO head, or using the HO pushrods on the renix cam (worn to the rockers, not the cam) might result with a potential issue. I figured possibly using new ones may resolve that somehow. Though I think I will just use all the HO stuff I have (except the valve cover) and call it good. Even though the parts have a few more miles than my Renix setup, they are a bit newer as well...

It looks like the soaking as at least loosened up a lot of stuff, or some at least. Going to try and see how much the power washer will get off tomorrow now. It is a 3000psi power washer so I imagine it will hopefully get the majority off, though it didn't really touch the deposits on the intake manifold, resorted to brake cleaner and a toothbrush for that. Took a few hours to clean up but it looks awesome now!

Thinking too I may go rent a valve spring compressor, or just buy one so I can pop out the valves one cylinder at a time and maybe take a scotchbrite pad and put it on the end of a drill just to get all those awkward round spaces and such cleaner... Any thoughts on that, or maybe an easier way to do it?

Thanks again

Paint

I meant why concerning the packing peanut deal.

cruiser54 said:

I meant why concerning the packing peanut deal.

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Oh lol. Apparently the peanut just gives the epoxy something to rest against to make a more consistent layer of it. It dissolves in water or whatever and won't clog anything so they say... I do have to say too, I feel like a TOTAL DUMBASS right now. I thought the head gasket was still on the block when I left. After the head sat for close to 2 days in the de-greasing stuff, and I then power washed it with a 3000psi power washer (got just about ALL of the gunk off it) When I was drying it off, I found what I thought was a small chip in the head. So I pushed at it with a screwdriver only to find out IT WAS THE HEADGASKET!! LMAO. It was still on so good it looked like it was part of the head lol. Peeled it off and it actually looks pretty good under there. I may power wash it again once I get the valves out, just to clean inside the head better.

With that development however, it begs the question, do I really even need to worry about the water jackets? They weren't originally blocked except by the gasket so I am not sure now. Most of all the write-ups I came across about water jackets and the 7120 head say to do it as they are going on the 258 block. So I am wondering if I should even bother with it now...

Paint

Don't worry about the water jackets. Put the motor together already!!

Yah, just going to do that lol. Bought new valve seals, a lapping tool and some compound, as well a nice Lisle valve spring compressor and the head gasket tonight. Had to order a different intake valve too since the one that came in had been used! That and they had to order the plugs in for me too... I may not need the valve, but figure it can't hurt to have it in case I need it once I check the other one out... Going to go through and replace the seals and clean inside the cylinders good, then lap them just to make sure I have good seals on everything... Got the head bolts and pushrods soaking in the de-greasing stuff while it is still mixed up and will clean those up too. Think a scotchbrite pad would be to aggressive to clean the pushrods up with?

Still have to get those bolts out too. May just find a place to do it if it isn't too expensive, just easier and quicker... Got part way drilled into one and dulled the bit, that and my extractors are complete GARBAGE! Just hope it isn't too much...

Don't think I need anything else so excited to get going on all this stuff. Having to work tomorrow so going to start tomorrow night probably. At least get all the valves pulled out and bagged/id'd, maybe start cleaning or at least spray some foaming degreaser inside everything. It is still pretty nasty in there lol.

Paint

what intake/exhaust upgrades are you making? I'm thinking of doing the same conversion for my stroker build, but don't want to change out the intake/exhause, just to keep things easier. Since you have all the pieces, can you tell if the Renix intake and exhaust will work with the 7120, perhaps with some light modding?

obaa-xj said:

what intake/exhaust upgrades are you making? I'm thinking of doing the same conversion for my stroker build, but don't want to change out the intake/exhause, just to keep things easier. Since you have all the pieces, can you tell if the Renix intake and exhaust will work with the 7120, perhaps with some light modding?

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The exhaust ports are the same.
I have done 2 HO engines into Renix Jeeps. I match ported the intake manifold to the Renix gasket along with matching the 7120 intake ports to the Renix gasket.

obaa-xj said:

what intake/exhaust upgrades are you making? I'm thinking of doing the same conversion for my stroker build, but don't want to change out the intake/exhause, just to keep things easier. Since you have all the pieces, can you tell if the Renix intake and exhaust will work with the 7120, perhaps with some light modding?

Click to expand...

I am not keeping ANY of the renix stuff coming off when doing these upgrades so won't be of too much help there lol. The ONLY thing staying from the systems being replaced on mine, is the TPS and that is because the newer ones can't be modified to work in a Renix computer system...

For the exhaust I am using the Banks Revolver header, and for the intake I am doing the 99+ intake manifold (2001 in my case though any 99+ would work). Aside from having to extend some wires on a couple sensors the hardest part of this conversion is going to be adapting the TPS to use my old one on the new throttle body. Over all there are a few write-ups and going by those it is pretty easy. Or I could buy Hesco's "kit" which makes it a bolt on, but costs $140 for basically a small piece of aluminum.

Assuming a complete donor manifold (99+) you would also need a newer power steering pump and tensioner bracket, HO throttle cable, 91-95ish fuel rail, fpr and injectors as well as body fuel lines, Possibly a cruise control cable (not checked to see if I can modify mine to work or not yet). No clue what else you would need for an automatic, all I own are sticks and will NEVER own an automatic EVER!

I am also converting the cooling system to an open cooling system, so eliminating the pressure bottle and all the split lines, then adding a splice in coolant cap and overflow bottle. Also putting in a K&N CAI kit. Eventually I am going to be boring the throttle body straight after the butterfly valve, adding a throttle body spacer and putting in the 703 Neon injectors. Still in the air on this one too, was going to be doing the alternator relocation modification (YJ upper bracket, ZJ lower bracket) but that requires me to do an electric fan conversion as well, not 100% sure if I want to do that right now or not... As for fuel lines, found something pretty cool I think is going to work nicely. Using 2 of the end of span fuel lines from an XJ (not sure what year they started but I know 2001's and 99's have them), and 2 of the under hood lines from a 4.0 ZJ, 100% stainless steel including the flex spots (braided stainless). Combining all that with a WJ booster and master cylinder, later model XJ prop valve with ZJ disk internals, custom stainless brake lines, Ford 8.8 with 4.10's and an LSD and disks, front later model D30 with 4.10's, Ax-15 from a 96 XJ and a np231 built with 6 pinion planetaries, SYE kit and HD chain and sprockets. Also doing custom rear bumper, modified Nates 4x4 front bumper along a TON of other things... Needless to say, this project got WAY the hell away from me lol.

Finally at a point now where I can say I am going no further lol. Doing the head swap gives me more power and mileage, and it makes EVERYTHING but the TPS adaptation a DIRECT bolt on. Once done with this I can finish the under the hood stuff and be done with it, then go nuts on the body work and finish this damn thing! I have just about all the parts I need so it will all be quite easy once I finish putting the head back together and get it on the block...

Hope this isn't all info overload here lol. It boils down to this, you have to adapt the renix intake manifold to the 7120 head by messing with the intake alignment dowels/holes. Then you still have the disadvantage of running the renix throttle body (smaller than HO) and all the other stock renix shit like the EGR. If you do a header, or later model exhaust manifold, and the 99+ intake you get the best of everything and the best power for not too much extra work. Also, the power steering pump from the Renix can be modified to work with the newer bracket, but you still need the new tensioner/PS pump bracket. If you are going through the trouble of a stroker, you might want to give some serious thought to upgrading the rest of the intake stuff...

Best of luck with your project,

Paint