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Stock Grand Cherokee Tech. All ZJ/WJ/WK Non-modified/stock questions go here!ZJ (93-98), WJ (99-04), WK (05+)
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After lots of reflection I decided to take the head back off.... I got into a hurry and started to have doubts that I cleaned the valves, pistons and head surface well enough. I reused my head bolts and the haynes manual says to only do so once so I need to buy new bolts. Also from what I read I should get a new head gasket instead of taking the risk of reusing the one I already torqued down once. I didn't check the block for flatness either and there is a spot between 3 and 4 where it is evident the gasket was failing. I guess I need to acquire a machinist straight edge and feeler gauges and check. Man I really don't want to have to pull my engine block and have to muscle it to the machine shop 60 miles away BUT I sure as hell don't want to have to go through all this BS again.
To top it all off as I was pulling the cylinder head off the big upturned plastic bin I was standing on broke and I fell through, dropping the cylinder head irregularly back onto the block and scratching the resurfaced area on piston #5 across the fire ring. It isn't a deep scratch but from what I understand it takes literally nothing to break the seal and cause another head gasket problem.
Really one of those "god I'm a *******" moments.
You think I should take it back to the machine shop and have the guy make another quick pass over it? He seems pretty chill and I can see him doing it for cheap. I'm just getting damn tired of hauling this big *** thing back and forth.
Personally, I don't think those scratches are as deep as the milling marks, so I wouldn't worry about it. JMHO, but do whatever you think you should.
It doesn't look like you recut the valve seats either. I would do that and grind in valve faces. You don't HAVE to, but as long as it's apart it's something I would do. That way, any cylinder pressure differences are a result of the rings. If you want to get fanatical about it, you can check the valve's seating with "Prussian Blue" on the valve faces lightly pressed into the seats. Artist's oil paint works just as well. From the picture, yours don't look bad. If the valves have wear grooves in them, I would have them reground. But that's me.
You can check the block deck by cleaning it up real well, LIGHTLY oiling it, and laying a piece of glass across it. That will show you any low spots that don't transfer oil to the glass. Don't press on the glass because that will flex it. A LIGHT pressure on the glass will show you how the gasket will seal it, but heavy pressure will flex the glass too much. Of course the head locator dowels get in the way.
This is just me passing on information I've learned over the years. I'm not trying to tell you what to do by ANY means. Hell, I've put together engines from bits and pieces that were laying around in a barn and just used them are they were!
OH.....I forgot! Put new valve stem seals in it as well.
New valve stem seals came with the gasket kit I bought so no problem there. I looked up how to reseat the valves and it looks pretty simple... Just have to buy some of that compound and suction cup stick thingy. My air intake valves look really bad.... Small pits all over the mating surface on all of them. The exhaust valves look good but I'll still do them also of course.
The glass and oil suggestion is a good idea! I cleaned the block surface again the best I could and tried it but I couldn't tell where the oil was once I pulled it off. Maybe I put it on too thin. Idk... Here is a picture of the questionable area on the block.
I still have the old gasket. The cylinder head side of it between the two pistons looks the worst so I am optimistic that maybe the cylinder head was the problem. I'm still going to buy a straight edge and feeler gauges to check just in case. I'll drive myself crazy thinking about it if I don't.
Also there is this rusty pit on the block.
It isn't on where the gasket mating surface is but should I still be worried about it?
Anyway all of your suggestions help me out a lot and are very much appreciated.
Last edited by Clayto1332; 12-20-2015 at 06:30 PM.
I probably should have told you to look THRU the glass to see the low spots! The oil will make the glass dark where it contacts the glass and light where is doesn't. I think if you check, those pits align with a cooling hole in the head and gasket but not in the block. That's because the coolant flow passages are different in the front and rear so the gasket can go on either way, as in upside down. You can use some fine sandpaper on a steel block to highlight the imperfections on the deck surface if you like. Judging from the cam sensor, that is between 3&4 which is right where I would suspect a warped head to blow.
Common practice today is to triple angle grind the valve seats at 30*, 45*, and 60* so that they are true in the center of the seat, and grind the valve faces at 0.5* more than 45* so they touch the seats only at the outer edges. Then, as they wear, the actual contact gets wider. Lapping was good enough for old engines like the 4.0, but high performance engines need special treatment to live longer. This is where you will find wear grooves in the valve faces. Also, as it was explained to me, lapping gets you a perfect seal at room temperature but that changes at combustion temps when the valves expand. Again, this is just info for future reference. I just happen to have taken a course from SAE on engine rebuilding. You can measure all your valve springs for straightness and free length to see if any are fatiqued. Likewise the rocker arms for wear pockets where they contact the valves.
I think that's enough picky stuff for now, don't you think?
There is a reason to be picky. Also I said at the beginning of this thread, I have no idea what I am doing. I'm becoming more and more glad that I pulled the head back off....
The bad looking valves aren't the intake, they are the exhaust. I thought the intake valves were exhaust because of the amount of black soot on them. Here is what all my exhaust valves look like:
Pictured is valve #1 and looks the worst. From what I am reading online these probably cannot effectively be resurfaced to the head and should be replaced with new. Also before I cleaned the head up I didn't pay close attention to the valve seal area but imagine it had tons of carbon build up. Hell, maybe my cylinder 1 misfire was a valve issue.... It would go away once the engine got up to temperature which is maybe because of the valve and head expanding.
Anyway I am glad I created this thread. I would have overlooked a ton of really important stuff.
I think you are right about replacing those exhaust valves. It looks like the sealing surface is curved from wear and if ground flat, the outer edge would be so thin it would melt and split.
More info; those exhaust valves run at around 1200* and are only cooled when in contact with the seat, which at high rpms, isn't often. Some heat is dissipated thru the stem, but not much. High output air cooled radial aircraft engines have valves with hollow stems filled with liquid sodium for cooling. I found out the new 6.4L Hemi uses this technology as well as roller valve lifters. My Dad told me that the Warbirds of WWII would occasionally break a valve stem and the resulting explosion blew the cylinder right off the crankcase!
The intakes will be in better shape because they are cooled by the incoming fuel-air charge.
This is why I went with a new head complete with valves and springs when I had to replace mine. All this stuff was new and only cost $455. The only additional charge would have been a $100 core charge if I hadn't returned my old one.
BTW, there is an FSB about cylinder misfire due to carbon buildup on the valves and what to do about it. This seems to happen with engines that are only run below 2500 rpm most of the time. They say the way to tell is to inspect the valve stem end where it contacts the rocker. The valves are designed to spin to maximize seat wear and if they are spinning, the stem will show circular marks and if not will show straight line marks.
LOL welp. I have a funny twist for you. Man, what a learning experience this has been....
I call the machine shop and talk to the same guy that did my head. I asked him about the valves, explained they are pitted and he said "yeahhh I have to look at it but I can do a valve job for 125, up to you whether you want to do that or try lapping the old ones". Like you said, new head with everything on it and set up 450 and this would put me at 375 for machine work only.... By this time I am really feeling the regret.
I borrowed feeler gauges and a straight edge from the auto parts store and check my block... I'm fitting a 5/1000ths gauge in a bunch of places. I'm really seeing dollar signs now. I sat down and invisioned myself buying a hoist and a mount, redoing the whole thing... Merry christmas!
Almost in tears I call machine shop guy back. Explained the whole thing start to finish.... He told me the edges of the block are likely burred up and can carefully smooth them out with a sharp blade or razor, staying away from the gasket seal surface. I start asking him if I need to do that before putting the head back on and then he tells me this:
"In the 25 - 30 years I have owned this shop I have never seen a warped 4.0 block. People take their jeep to a shop, they take the head off, I resurface it, they pick it up and put it back on. That's it. If you keep nit picking at all these little things you are never going to finish. Nothing will be good enough. I think you have been listening to too many people and reading too much bull**** off the internet."
And there it is! He said I could reuse the gasket I already torqued down as long as everything is clean and smooth. I'm still going to buy new exhaust valves and lap them in I think. Other than that I'm ready to get back up and running.
Yes, he's right. The head gasket is thick enough to seal small imperfections. The only important part is the steel fire-ring around the cylinders. I'm sorry if I gave you too much to think about. I guess I'm an perfectionist when it comes to engine rebuilding. Most of the engines I built were drag racing engines. I think you should do what you said with the exhaust valves.
One thing I WILL say is make sure your head bolts are oiled before you put them in. Those rusty holes need to be cleaned out so the torque will be accurate. You've probably heard of "hot torquing"? What I've found is bring the bolts up to max torque, then have a beer or cup of coffee. Then after a while torque them again. After a short run of the engine, AND A COOLDOWN, check the torque and they probably won't have changed.
Dude, do not apologize. If it weren't for you I would be driving a ticking time bomb around.
I asked the guys at the auto parts store about my valves. Showed them a picture and they told me to bring the block and head up there. Turns out they have an angle grinder and used to do head work (before these overhead cam engines came about). He got one grinded down all nice and smooth. It was cutting it close.... But then he took it and banged it down in the valve seat over and over. When he took it out there was a perfect ring all the way around the newly polished surface EXCEPT about a centimeter. He said "this ain't good" and advised me to take it back to the machine shop.
SO... If I would have listened to you I could have bought a brand new bad *** head with all the hardware. I'm going to take it in the morn and he said he would try to bang it out by wednesday at close of business since they don't reopen until the following Monday.
Merry Christmas! If you have any more questions, you can PM me. Just click on my signature header box, a pop down menu will show you "send private message."
Absolutely! I love to teach. As a toolmaker, I had 4 apprentices during my tenure that I brought up to NY State Journeymen standards and they got their certificates. Unfortunately, I don't have the creds to teach professionally and nobody is teaching basic metalworking now anyway except in tech schools. Almost 50 years as a toolmaker and now I do everything with a drill and sawzall. I don't have the power equipment to do much else.
Good luck with your jeep. She'll be purring shortly.
As I was read through this I started wondering why you got a head back from the machine shop without valves. Good deal on having them do the valve work as well. I generally do not oil head bolts, but I do clean out the threads in the block really well. The rust on the driver's side is common on the Jeep heads I've pulled, both with head or head gasket problems. Use the Fel Pro head gasket and remember the front left bolt gets a lower torque and thread sealer. Use new head bolts. I would change all the rubber bits while you are in there, including the grommets and elbows on the valve cover.
Yeah I took it to the machine shop and got it back without the valves because I am clueless of what I am doing. I'm stubborn and don't like other men working on my vehicles. It's a pride thing....
Anywho I took the head back to the machine shop this morning and around 4:30 the guy already called and said he was finished and I could come and get it. My wife was in Wichita Falls at the time but she wasn't answering her phone and it was 20 minutes until they closed for the day so I'll just have to make a trip tomorrow. I asked him again about the gasket this morning and explained the one that came in the kit was 3 pieces of metal riveted together. He pondered whether or not I can, or should, reuse it so I told him I would buy whatever type of gasket he thinks is best. He said he would have one when I came and got it. I didn't ask what brand or type... I had my auto shop order head bolts and they will be here in the morning. The kit with the head gasket came with a valve cover and all of its rubber pieces. I had just changed all that out the week before but might as well use the brand new. It also came with "O" rings for the fuel injectors which I had also changed out the week before. However the new rings I had bought seemed loose and not so good. I think I will change those out again as well.
BTW it is the front RIGHT bolt that gets the sealant and 100 ft lbs of torque! I hated to correct you but I would hate even more for someone to read this thread and become misinformed. You know... Someone like me that doesn't know anything.... LOL
I bought some high-heat paint and am fancying the idea of painting the valve cover. Maybe the exhaust manifold, water pump, thermostat housing, fuel rail etc tonight. Only problem is I am really lazy and probably won't do it. I DID see a compression test kit for 20 dollars at harbor freight earlier but jew'd out at the last minute. See? I'm the kind of guy that will blow 20 dollars on paint that I probably won't use but won't buy a 20 dollar compression test kit that I SHOULD run after I get the thing put back together so I will know if I am having piston problems. In fact me cheaping out is why this mess has drug out for so long.
One last thing I thought I would share. I asked the machine shop guy again about the head and that I could fit a 5/1000ths gauge between cylinders 3 and 4. He explained that this was gradual and I shouldn't worry about it. The warpage that is problematic is when it warps that much within a much shorter measurement. This pretty much contradicts everything I read everywhere (Haynes manual and on internet) but I have dropped his name to a few people in the automotive industry around here and everyone says he has been in business for many years and is highly respected. Just food for thought.
Hell, he even told me I could reuse the bolts again as long as they were still in good shape! Even though the Haynes repair manual tells you that you can only do it the one time. 20 dollar set of bolts? I'm not going to chance it. I'm already out around 500 ~ 600 dollars so far and I imagine there will be other issues after we get everything hooked back up and try to crank it for the first time (because again, I don't know what I am doing).
Last edited by Clayto1332; 12-22-2015 at 05:46 PM.
Okay, I'm going to throw another iron into the fire. Did you check the straight-edge for straightness? I've found over the years that steel straightedges, especially ones the are beveled on one side only, will warp with atmospheric changes like temperature (cold to hot) and not always stay straight. If it is NOT single edged, try flipping it over and using the other side. I'm a guy that has used granite surface plates and dial indicators all my life.
.005" is nothing to worry about unless it's in a small area like the web between 2 cylinders. In order to check that, you need a short straightedge that just spans the 2 cylinders and not much beyond. Again, that's what the steel "fire ring" around the cylinders on the gasket is for, to maximize pressure in that area and prevent burn-out.
About the head bolts. Some modern engines use a "torque to yield" type of bolt, where they are designed to actually stretch. When I did the head on my wife's Dodge K-car 4 cyl. the torque spec said "torque to XX, then turn 1/4 turn more". WHAT? That's why you should use new bolts on any engine now. It just good practice anyway. On oiling the bolts, if I've run a tap thru the holes and are sure they are clean, I don't, but if not, I lightly oil them. It's just what I do, nothing more.
The jeep 4.0 is a trusted reliable engine and seems to run forever, even with barnyard rebuilds. I seriously doubt you'll have any problems with it after this. JMHO.
12-20-2015, 01:59 PM
