Engine inspection
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*[[AMC V-8s]] | *[[AMC V-8s]] | ||
| − | ==Estimating stroke== | + | ===Estimating stroke=== |
There can be cases where the casting numbers can tell you what you need to know. But in cases where the engine might have had the crank changed to a different stroke, the displacement won't be known. The most important thing about finding the displacement is the stroke because the bore will be very close to whatever the nominal bore size is for the casting number of the block in question. | There can be cases where the casting numbers can tell you what you need to know. But in cases where the engine might have had the crank changed to a different stroke, the displacement won't be known. The most important thing about finding the displacement is the stroke because the bore will be very close to whatever the nominal bore size is for the casting number of the block in question. | ||
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Remove the breather and PCV to look for obvious signs of sludge. Check cooling system for rust and the radiator for clogged tubes or evidence of leaks that could have caused overheating. | Remove the breather and PCV to look for obvious signs of sludge. Check cooling system for rust and the radiator for clogged tubes or evidence of leaks that could have caused overheating. | ||
| − | Next, start the engine and warm it up. Remove one spark plug wire at a time using an insulated spark plug boot puller, noting any change in idle speed. If the idle speed drops, that cylinder was firing. Go through all the plugs and if there was a plug or plugs that the idle speed remained unchanged or nearly so, the next step is to see if it's a problem with the plug or wire. Remove the plug wire from the weak cylinder and swap it with a plug and wire from a cylinder that was working normally. If the weak cylinder is now OK, it was either the plug wire or the plug. Swap the wire from the weak cylinder with another good wire and see the results. If the miss followed the wire, the wire is bad, If not it's the plug. | + | Next (assuming the engine can be started), start the engine and warm it up. Remove one spark plug wire at a time using an insulated spark plug boot puller, noting any change in idle speed. If the idle speed drops, that cylinder was firing. Go through all the plugs and if there was a plug or plugs that the idle speed remained unchanged or nearly so, the next step is to see if it's a problem with the plug or wire. Remove the plug wire from the weak cylinder and swap it with a plug and wire from a cylinder that was working normally. If the weak cylinder is now OK, it was either the plug wire or the plug. Swap the wire from the weak cylinder with another good wire and see the results. If the miss followed the wire, the wire is bad, If not it's the plug. |
If the miss did not follow the plug or wire, that cylinder or cylinders need to have a compression test performed on them. With the throttle propped wide open and the ignition disabled, crank the engine over letting the cylinder come up on compression three times. Note the reading. Next, squirt oil into the cylinder through the plug opening and test again. If the reading doesn't change, likely the valves aren't sealing. If the pressure comes up, there's a good chance it has worn or possibly broken rings. | If the miss did not follow the plug or wire, that cylinder or cylinders need to have a compression test performed on them. With the throttle propped wide open and the ignition disabled, crank the engine over letting the cylinder come up on compression three times. Note the reading. Next, squirt oil into the cylinder through the plug opening and test again. If the reading doesn't change, likely the valves aren't sealing. If the pressure comes up, there's a good chance it has worn or possibly broken rings. | ||
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| + | {{Note1}}While buying an engine that cannot be started is not the best plan, sometimes this may be the best available option. In that case, plan on doing at least a leak down test. This does not require the engine to be started or even cranked over like when doing a compression test. However, it does require a compressor, a leak down tester and tools to remove the spark plugs and to turn the engine over to TDC for each cylinder. | ||
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| + | Info on leak down testing including a link to an article on doing a proper leak down test can be seen [url=http://www.crankshaftcoalition.com/wiki/Leakdown_tester_homemade_engine_cylinder_troubleshooting_tool][B]here[/B][/url]. | ||
===Some points to check:=== | ===Some points to check:=== | ||
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