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engine parts teardown

Rebuilt is a relative term. This is especially true when used in conjunction with the word engine. On the low side of an engine rebuild is a can of motor honey poured into the crankcase and a set of crossed fingers behind the salesman who hopes the rod knock will go away just long enough to get the car off the lot. Legitimate rebuilt engines are in reality remanufactured. Engine teardown and inspection is followed by machine work. Every part is returned to original or better-than-factory tolerances. The process essentially brings an engine back to new. The middle ground is anywhere in between the motor honey and remanufacture, and why the phrase 'rebuilt engine' holds broad meaning. The catch is that determining if the engine needs a complete rebuild or will benefit from a freshen-up only becomes apparent with the engine out of the car and apart.

Engine Removal
Sometimes there are enough things wrong with an engine that fixing them with the engine out of the vehicle makes more sense than trying to struggle through the work with the engine in the car. A compression check can shed light onto problems that only engine removal and disassembly will completely reveal. A combination of low compression in one or more cylinders combined with a timing chain or chains beyond their expiration date is a good example of an engine best removed for service. More obvious engine wear problems manifest themselves as rod knock or clouds of oil smoke pouring out the tailpipe. Add a spent clutch or leaky rear main seal to the fix it list and out comes the engine hoist.

Engine Disassembly
With the engine out of the car the disassembly and inspection process is the next step. This process itself will determine the extent of the rebuild required. If an engine is just a bit tired but otherwise sound, then a re-ring or re-bearing can be the answer to freshening up stock engine performance. In this case the rebuild fell into this middle ground. Fresh rings and bearings were installed along with some new timing chains. The engine freshen-up return depends on the investment. A hastily rebuilt engine will fall right back into disrepair the same way stars and celebrity fall back into their old bad habits after a cursory stay at rehabilitation. A thorough inspection and meticulous rehabilitation can give even tired old engines a second chance.

Tools for the Job
Here are the things you'll need to do the job: A service manual, an engine hoist, an engine stand, a sturdy chain, a place to park the car while relieved of its engine, hand tools, one-quart plastic zip bags, a felt marker, a punch marking set, a digital camera, and a rubber hose.


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Photo Guide
engine compression check
A static compression check is the first step to finding out what's right or wrong inside the engine. In this case, one cylinder had low compression and the timing chains were making an unnerving racket. The engine had logged over 100K miles. The decision was made to yank it out and put it on an engine stand to see what was going on.
engine pull engine removal
Before yanking the engine, spend a good deal of time taking "before" pictures and labeling all electrical connectors, vacuum lines, and any other easy-to-forget things while still together. Park the car where it doesn't have to move for a while. Wheel chocks will prevent any unwelcome rolling.
engine lift removal hoist
Follow the procedure outlined in the manual for engine removal. Get some one-quart plastic bags. Label them Starter. A/C. Intake Manifold. And so on. Use the bags to store nuts and bolts. Mark the hinges for reference and remove the hood. Use the hoist and a chain to remove the engine from the car for transfer to the engine stand.
engine disassembly
With the engine on the stand, begin disassembly and inspection. Remove the cylinder head or heads. Remove the oil pan, harmonic balancer, timing cover, and any other external parts. Take more photos as you go for future assembly reference. Keep bagging bolts by sets.
engine internals removal
Now it's time to remove the engine internals. Flip the engine over and remove the connecting rod nuts and caps. Any stubborn connecting rod or main bearing caps can be convinced a tapping with a plastic faced hammer. Never strike bearing caps with a metal hammer.
engine connecting rod bolts
Thread a bit of rubber hose over the ends of the connecting rod bolts so they don't nick the crank journals on the way out of the engine block. Remove the pistons and rods by pushing them through the cylinders from the bottom.
engine parts assembly
Marking parts is of vital importance. Everything has to go back together exactly the same way it came out. Use a punch set to mark and index main caps, connecting rods, and any other parts not marked. Keep bearings together and mark backside with a sharpie.
engine crankshaft main caps bearings
Remove main caps and bearings. Remove the crankshaft. Inspect the bearings and crankshaft journals for uneven wear, scoring, and anything other than smooth. Scoring on journals that can be felt with a fingernail means the crank has to go out to the machine shop. Black carbon on journals or bearings is a very bad sign.
engine reading parts surfaces
Inspect the engine by reading its parts and surfaces. Excessive vertical scoring on the cylinder walls or molten pistons are sure signs the engine block will have to be sent out to the machine shop. This Mitsubishi G54B turbo engine still showed factory crosshatch finish hone on the cylinder walls after 100K miles.
engine pistons cleaning
Further cleaning of pistons in a chemical dip will remove carbon deposits for a closer look at piston ring condition. All told this engine looked like it could get by with some new timing chains, fresh rings, and a set of bearings. A new cylinder head will also be part of the rebuild. We'll make all it all happen over the next few installments.


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