The 1981 CJ-7 my brother acquired a few years ago still had its original, though showing its age, 258 engine. It had a fair amount of blowby due to worn rings. Oil collected in the air filter housing causing a mess over time. The Jeep came with the stock Carter carb, which wasn't working very well. He swapped to a Motorcraft 2100 (or 2150?), which after reworking by a local carb guru ran pretty well.
Several months back, something in the engine suddenly conked out, causing a loss of power and "Oh $%&!, that's going to be expensive" sounds. We towed the Jeep home, pulled the spark plugs, and found that the end of one plug was badly bent/broken.
We then pulled the head and found metal bits in one cylinder that weren't from the ruined spark plug. After some researching, head scratching, and asking around, we figured most likely a ring had broken and somehow flung a piece up past the piston into the top of the cylinder, though a dropped valve guide or such is also a possibility. It didn't really matter. All of the cylinders were scored badly enough, and we knew the engine already had a fair amount of blowby. The bottom needed to be rebuilt. And, of course, the head should be redone too if going that far. Rebuild the whole engine.
With money being tight, and some health issues pressing, Paul took a gamble buying a used 258 motor. It was out of a 1984 Scrambler, with supposedly 98K miles on it.
The seller said the engine ran great when pulled 2 years ago, and should give another 100K miles. Yeah, right. IMO, that's a very ambitious estimate at best. But, it may be in good shape. Or not. We knew it was a gamble despite the claims. "Running" 258's are hard to find around here, so Paul decided to go for it. $600.
We drove a 200 mile round trip picking up the engine. The seller seemed sincere. Upon closer examination, it is not an unmolested factory engine, though I don't recall if the seller ever claimed it to be. It is fairly obvious from the liberal use of blue RTV on almost everything where anything joins -- from the cork oil pan gasket on up the whole motor -- that someone has had this thing entirely apart. Even the EGR valve body has some RTV (though orange or red there, IIRC). What sort of mechanic would RTV an EGR valve? The intake/head gaskets are a hodgepodge of whatever mashed together, not factory.
We swapped engines (well the remaining block for the used engine), which took us about 5 days working in the afternoons.
Before I continue, I want to say that I am not a mechanic. However, I am not ignorant about the basics. I've worked on vehicles over the years troubleshooting and replacing some basic things. And, I've reached a bit beyond that at times. Two years ago, I took on my most ambitious project, which was successfully rebuilding the 22R engine in my Toyota by myself. When I get involved with something, I tend to delve into researching and learning a lot about it. If you'd care to see how detail oriented I tend to be, skim all the way through my rebuild thread at yotatech: http://www.yotatech.com/f116/22r-rebuild-192584/
I mention the above to provide the only basis of qualification that I can offer online to show I'm not a total dummy.
The seller, when Paul contacted him by phone today, indicated that anything possibly wrong with this engine must be our fault, that we must have done something wrong to screw it up. I don't accept that. I make my share of mistakes, at times more than most, but I don't think we did anything wrong here.
I'll list below how we approached this supposedly previously wonderfully running engine that had been sitting for 2 years. Did we miss anything crucial, or do anything wrong? Would you have approached it differently? If so, how?
Got it put in. Aligning the shaft to the tranny was a lot of fun. I see why some prefer to pull and install the whole shebang as one unit. We eventually got it stabbed in and everything bolted up.
Removed the oil filter and drained the oil. The oil was filthy black, though there were no signs of water contamination. Some fair sized metal chunks drained out of the pan. Uh oh. Couldn't tell what they were from. Put on a Napa Gold oil filter and refilled with Quaker 10w30.
Pulled the spark plugs. They all looked ok. The middle ones appeared to have been running a bit rich compared to the outer. Maybe that's normal? No evidence of oil burning on any. Sprayed a 1-2 second shot of WD-40 in each plug hole.
Turned engine to TDC on the compression stroke using a wrench on the crank pulley. Engine turned very easily. The rotor was pointing at #1 position on distributor. We inserted a wood dowel in the #1 spark plug hole and rotated the engine back and forth to assure that everthing was lined up. I had read that the timing mark portion of the harmonic balancer can slip out of alignment, so it is best to make sure everything is right before trusting it for timing. This one was. At true TDC (by testing the piston itself with the wooden dowel), the timing mark was aligned within a couple degrees.
While set at TDC, we used another short wooden dowel to mark the distance from the firewall side distributor cap screw hole to the engine block. That would allow realigning the distributor body in relation to the engine. We also marked and mentally noted (it aligned with a part in the dist body) the rotor's relation to the distributor body. Then, we removed the distributor.
One of Harbor Freight's finest $.50 screwdrivers was sacrificed to make a tool to spin the oil pump. We cut off the handle and chucked the blade portion in a drill. It worked great to spin the pump and wasn't difficult to keep away from rubbing the sides of the dist shaft hole.
The oil pump turned easily at first, but then quickly built oil pressure. Thanks to all who contribute info in forums, I had read that rotating the crank while priming is likely necessary to send oil through everything. So, we did. We spun the drill at TDC, turned the crank, spun again for 20 seconds or so, and so on, until we had turned the crank 2 full revolutions to put us back on the compression stroke at TDC. Reinstalled the distributor with both it and the rotor in the same positions as they were originally.
Here is a good time to mention my concern about timing issues. We were putting an 84 engine into an 81. If you read about the Nutter bypass, which eliminates the computer portion of the post 82 or whatever year models, it mentions needing to readjust the timing to compensate for the lack of computer action. Or something like that. I remember thinking it could be off. We decided to leave the timing as it came, presuming the engine would at least start.
After the distributor was back in, and while plugs were still out, we cranked the motor over for 10 seconds or so with the starter to make extra sure everything was well lubed. Then, we gapped and installed new plugs.
Before starting, we capped off all vacuum lines not used.
The engine cranked and cranked. No gas to carb. The fuel pump was bad. Replaced it. That's even more cold cranking to lube things up.
Cranked some more. The engine wanted to catch. It finally started and ran with a loud knock, but quickly died. We played with timing and the carb mix (ended up at about 3 turns out on the Motorcraft carb), and finally got it going. Original timing was way off, like 20+ degrees off. We set it to about 8 BTC with the vacuum advance line disconnected. As for how rich we had to run the carb, I suspect the EGR valve may be at least partially stuck open. We've looked everything over several times and don't see ay potential sources of vacuum leaks.
The engine runs, but it has blowby like none I've ever seen. The chimney of oil smoke it spouts out through everything (PCV hose through carb base as well as out the dipstick tube would make an old railroad locomotive proud.
We drove around the block and came home with our eyes watering from the smoke. No way will this pass emission testing. And, you'd need to wear a gas mask to drive it.
So, it seems we're back to square one.