I was just going to replace a single broken exhaust bolt in my 1979 Jeep Cherokee Golden Eagle’s cylinder head, when I discovered some major issues that threaten to turn this “short” repair into a genuine time-suck. This phenomenon is called “mission creep” and for decades, it’s been plaguing wrenchers around the world.
“Mission Creep” involves gradually changing your project plans, usually from something relatively simple to something time consuming and complex, often after finding unexpected imperfections. This happens to all of my friends and me as we fix our vehicles, and has resulted in significantly more time spent wrenching than actually driving.
Yesterday, Mission Creep reared its ugly head on my beloved 1979 Jeep Cherokee Golden Eagle project, and now I’m worried that this beautiful machine that deserves to be driving on America’s vast highways, will be under the knife indefinitely.
The AMC 360 V8 engine in my Golden Eagle seemed totally fine when I bought it, aside from a stutter under acceleration that I was convinced was a simple issue of spark timing. Still, one little thing bothered me: there was a broken exhaust manifold bolt in the passenger’s side cylinder head.
And because this Jeep is, by far, my nicest vehicle, I wanted to make sure it was in tip-top mechanical shape. So I decided to yank the head.
My friend and I toiled for hours in the blistering heat, removing the accessories, the radiator, a bunch of electrical wiring, the intake manifold, and the exhaust manifolds (one of whose studs I broke), the rocker arms (my friend broke a rocker arm bridge—see above), and pushrods. From there, the cylinder head bolts came out, and the head just needed to be lifted off—for the first time in 39 years. This was not easy.
I wont’ go into how long we had to hang off a pry bar to get that one head off (the driver’s side one is still in place), because it might make me short out my laptop with salty tears. But suffice it to say: I still have scars.
Eventually, I was able got the offending cylinder head off, and observed the broken exhaust bolt up close:
I plan to take it to a machine shop, and have them extract it, since I don’t trust my welding skills enough to risk messing up that exhaust manifold gasket surface.
But that initial objective was relatively painless. What wasn’t painless was inspecting my motor. That’s the intake manifold above, and if you look closely in the runners, what you see is a dark abyss of wet oil:
This is, obviously, far from optimal. Neither is this extremely sludgy valve cover:
But what concerned me most were the cylinders. It wasn’t just the carbon buildup on the bottom of the cylinder head:
Nor was it the crust on top of the pistons:
No no, my biggest concern hit me when I looked at the cylinder walls (note: the liquid below is oil that I poured in to prevent oxidation).
There are tons of vertical scoring marks on the walls. And on the rearmost cylinder wall, there’s an even stranger pattern featuring numerous circumferential rings:
Worse yet is just how tall the lip is where the piston rings stop riding on the cylinder walls. This lip is an indication of cylinder wall wear, and—while some of the lip is likely carbon buildup—the thing feels about as deep as the Mariana Trench.
I didn’t notice a ton of smoke coming from my tailpipe when I drove the Jeep last spring, but then, I wasn’t paying much attention. I really should have been, and I should have done a compression test, too. Because now I’m worried.
I’m concerned that these cylinder walls are worn out, and that the oil in my intake is caused from combustion gases getting past the rings, and into the crankcase—a phenomenon called “blowby.” In other words, part of me wants to yank this motor and do a full rebuild.
That’s a far cry from that initial “extract and replace a single bolt” mission.
I still haven’t decided what my plan is. I could just replace my gaskets and seals, slap in some new bolts and rocker arms, throw the engine together as is, and hope it doesn’t burn too much oil. This thing wont’ be on the road during Michigan’s harsh winters anyway, so it’s not like I need to put a ton of miles on it.
Does it make sense to do an expensive rebuild on something I’ll only put a couple of thousand miles on a year? Should I allow this much Mission Creep ? I haven’t decided yet. But I am deeply concerned about this Jeep now—something that wasn’t the case before I took that dang cylinder head out.