BotakBeng

Here is a good video for your references.

Kalali

Watched that video at least half a dozen times before taking the plunge...Great reference. Well, separating the exhaust manifolds from the down pipe did not work out. Just couldn't get a socket on the bolts but did manage to push them aside enough to remove the head. Now the wait begins until the new head arrives from Clearwater. In the meantime I'm going to replace the hoses and might even replace the waterpump. Depending on the cost of the injectors I might even put new ones in there. Anything else I should attend while I have everything apart? I have owned my XJ since new and an aside from fluid changes and tires and with the exception of the belt and an alternator nothing has been replaced within the 175K miles or ownership.
Quick question: How did you folks take the short dowels out of the head? They don't seem to budge no matter how much I try.

BotakBeng

Quick Q for you....did you remove the 80lbs head by yourself?

RenegadeT

new head should have dowel pins in there.

might want to change motor mounts while the intake is off. I would say def. do it if you had the exhaust manifold out. After 175k, they gotta be toast.

5-90

I have - head and manifolds as an assembly, several times on several different rigs - but I'm a fairly large individual.

It can be done, but I usually recommend either having a helper you trust or having an engine crane.

As far as removal of the manifolds - I'll usually pull the head as an assembly and service the manifold gasket on the bench, it's easier that way. A 9/16" "flex" socket (shorty socket with inbuilt universal joint) can make it easier to service the rear lower manifold screws in situ, once you get the airbox out and start playing with extensions. But, I'll pull the whole top end and service everything on the bench, if the head's coming out anyhow. Saves a lot of swearing and knuckle skin.

Manifold collector nuts I usually replace with half hard brass pieces (3/8"-16 thread, most years,) which saves trying to wring them off later. Manifold screws get replaced with silicon bronze or aluminum bronze (half hard or full hard - reports from the field indicate that a number of these pieces are now being shipped "full soft" and failing on install, but heat-treatment of cuprous alloys is simpler than for ferrous) so either check or do the heat-treat yourself (there are a number of useful references online for the Googling.) Why replace the screws? Same reasons I replace the collector nuts:
- Brass and bronze will not seize against steel.
- Copper alloys respond to heat-cycling opposite to ferrous (ergo, they'll actually get incrementally stronger over time, instead of weaker. If it's been better than 100kmiles since I put them in, I'll usually anneal them slightly before they go back in to extend their lives. Steel fasteners that come out get thrown away.)
- Never-seez isn't really a good idea there, so brass/bronze obviates its use
- The threads are easier to deform on cuprous alloys, therefore allowing the modification of the fasteners to make them intrinsically self-locking.

I'm sure I've got a couple more, but those are the primary reasons. If you can't get brass/bronze, get SAE5 instead of SAE8. Yes, I know that the OEM fasteners are SAE8, but the OEMs usually make decisions like that to bring the costs down and simplify logistics. Just because it's OEM doesn't mean it's the best solution...

Why SAE5? Because after 40-50 heat cycles, SAE5 steel will retain more absolute strength than SAE8 (experimentally verified - SAE8 is more sensitive to heat cycles than SAE5.) Maybe it doesn't make them so weak that they'll snap - but it can, and it has (and I've made a few bucks getting ruptured screws out of cylinder heads and engine blocks over the years...)

Kalali

I did but don't recommend it. One wrong move and you could hurt your back. I'll get some help when the new one goes back on.
Looks like Jeep engineers didn't get the memo that aluminum is lighter than iron.....

5-90, thanks for great input on the nuts and bolts. I sure hope I will not have to do this job again...

01cherokeelimited

this video should be shown in theaters... for real. I think I'm gonna have to be doing the same thing on my xj soon. Definitely going to watch this again!

5-90

Aluminum may be lighter than iron, but the use of aluminum heads with iron blocks lead to the development of MLS head gaskets - because the differing rates of thermal expansion causes head gaskets to "scrub out."

Also, it should be borne in mind that AMC was almost always behind the eight-ball, in an engineering sense. They only had two four-cylinder engines (the all-iron 4-150, 1984-up, and the all-aluminum V2-108, early 1960's) and they did do an aluminum version of the 6-196. That's also why the AMC V8s all had forged internals - they were trying to bring these things to market quickly, and didn't have the time or staff to refine the design. So, they went with what worked and worked well.

However, iron is more reliable. I know there's an aftermarket aluminum head for our beloved I6, but I'd not mind an aluminum block to go under it for a "total solution" (this is why the Buick/Rover V8-215 was such a damned durable engine. We used it for 3-5 years here, then Buick sold the tooling to Rover because the engine wasn't popular here. Rover used it for thirty-plus years, and refused to sell the tooling back to Buick about 20 years ago.)

Also, a quirk of aluminum parts is not that you can run higher compression under them, but you must run higher compression, in order to keep combustion temperatures up. While higher compression can make for greater combustion efficiency, higher compression also tends to lead to formation of NOx - which is generally easier to control in iron than in aluminum (because lower CRs can be run without too much trouble.)

Even running Al/Al can be sketchy - for starters, the block must be sleeved. If a "dry-sleeve" block gets too hot, it's possible to drop a sleeve. If a "wet-sleeve" block gets too hot, the sleeves have to be pulled and resealed (the Waukeshaw four-cylinder industrial engines were designed with this in mind - sometime after the third oil change, it looks like you're draining a chocolate milkshake, but this is perfectly normal for that engine! Just keep an eye on your coolant level, as long as you're just "weeping" an taking 1-2 weeks to lose a pint, you're still good...)

I'd have to work pretty hard on the design to get an all-aluminum engine I'd feel good about running "out in the Bush." Iron was more common with off-road gear simply because it is more reliable and easier to keep in service (if you overheat an aluminum head, it will warp about twelve times in ten. Overhead an iron head, and it's about 3/10 you've warped it. And, it's easier to grind the deck on an iron head.)

Aluminum parts are also labour-intensive - whenever I've overhauled an all-aluminum engine, or overhauled aluminum heads, I've always put Heli-Coils in all of the screw holes to improve clamping forces. Then again, I was working with some real fire-breathers...