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Teardown - 1.
Drain any used engine oil into a bucket or pan for inspection. Use your sense of smell here too and don’t be afraid to get dirty. Water or a light brown chocolate milk substance is bad and means water has gotten into your block. Look for metallic shavings or chunks of steel. Ours was black as night and smelled of old fuel; we gave it to Editor Stanley as Christmas gift cologne.
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Teardown - 2.
Before the major deconstruction begins, get boxes or bags to place bolts and hardware in. Tag them too. If you are going to use sandwich bags, take the PBJ out first and use freezer bags so they don’t tear open.
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Teardown - 3.
We pulled the valve covers first and discovered very little engine buildup or “gunk”. A sign that the oil had been changed regularly by the previous owner. Good-good!
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Teardown - 4.
A quick glance at the top of the heads and rockers showed nothing amuck. Pushrods were tight and everything was in alignment.
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Teardown - 5.
Closer inspection revealed mismatched bolts and different markings on the rockers. Casting marks were searched online, which revealed that the heads were from a 1977 AMC 360. It was becoming clear that at some point this engine had been cannibalized.
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Teardown - 6.
We pulled the rockers and all the push rods. If you plan on reusing any of the parts it is best to keep them organized and mark what location they came from. To check for bent pushrods, grab a piece of glass and roll the rods on them, any wobbling will be apparent, and a sign of abuse. All 16 of ours were straight.
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Teardown - 7.
Lifters can come out of the block with pliers or a magnet. If you have a roller cam, ensure that the rollers turn smoothly. For a flat tappet cam like our engine has, use a straight edge to see if the lifters are still convex. All of ours were concave, hinting at oil starvation or, seeing as we knew the engine had been opened up before, inferior parts or break-in procedures could be to blame.
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Teardown - 8.
The top of the valve stems can tell a story as well. Most of ours showed little wear, but a few had small divot marks like those on the right intake valve.
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Teardown - 9.
To pull the heads, loosen all the bolts a little at a time to relieve the stress evenly. When all the bolts are out, lift the head straight up to avoid damaging the alignment dowels. Scour the heads like a hound after a squirrel. Look for valve damage, cracks between cylinders, gasket failures, or anything else unusual. You can even put a straight edge across the heads to check for level. Something caught our eye…
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Teardown - 10.
A very bad exhaust valve. Notice the two cracks on either side? This is a burnt exhaust valve. They are normally caused by a poor mating surface with the valve seat or a build up of carbon on the valve. This sort of damage also occurs when an engine is overheated. It’s not a deal breaker, but if you plan on keeping the heads, you will have some additional machining costs to repair.
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Teardown - 11.
Try to keep the head gasket intact after taking the head off. Look for cracks, blow-by, and coolant leaks or burnt sections, all are bad, but repairable. Many head gaskets are stamped with a manufacturing date, as are engine bearings.
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Teardown - 12.
Looking into the cylinders with the head off revealed VERY little wear. You may feel a slight ridge at the top of the piston holes where the piston rings stop. Burn marks, holes, rust, carbon buildup and many other signs of abuse or impending doom may greet you at this point as well. Using a set of simple calipers told us that this block has never been bored out and was still factory fresh. We are making progress, but are only half way done on the teardown. Read up next issue on what other gremlins we find lurking in the Menace.
Story & photos by Bryan Irons
Merican Metal Menace – Engine Autopsy
Words never uttered while behind the wheel of Stinky Jeep would include “powerful”, “smooth” and “low maintenance.” Now we can add “reliable” to the never-to-be-used-again descriptors of the 304 AMC V8. Oil pressure in the single digits and valves that sound like a jogger with a pocket full of change were some of the last nails in the coffin before we pulled the trigger on an engine build. We’re going to cover the whole thing here in 4WDrive from teardown to a dyno run to see where we end up. We wanted something that would make for an easy swap, make power in the 1hp/cu range, be reliable to run in traffic, and easy to make upgrades in the future. Presenting the Merica Metal Menace 401 AMC.
The choice of the 401 AMC was a risky one as they are becoming harder to come by. AMC’s V-8 architecture remained almost the same between their engines ranging from 290 cu up to the massive 401. Minor differences occur, as with any mass produced engine, so do your homework when deciding on what suits your build needs. Sure, the pedestrian 360 cu version would have fit our build specs just fine and are much easier to source, but the added displacement of the 401 coupled with the much stronger forged steel crankshaft could not be ignored. Lucky for us, we “knew a guy” who happened to have one lying around. A deal was struck to score the vintage block that was scavenged from a 1974 Jeep J-20.
With the block in our possession, it was teardown time and we were ready to take a peek at what we had to work with. Follow along as we show you a few ways to check for previous owner shenanigans and what to look for in a good seasoned engine block before shelling out your hard earned clams on a potential Metal Menace.
Read next issue's Stinky Jeep Part 2 - 2nd installment of Merican Metal Menace.