engine noise=lifter or piston slap??
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engine noise=lifter or piston slap??
my engine just started tapping noticeably recently. it sounds like a lifter to me, and goes up with the rpms.i tried changing the oil , that being mobil 5w30 clean 5000, and 1 quart of lucas, still tapping. would thicker oil help? maybe some 15w40? even though my engine has 275k on it, it hasnt done this before except on rare occassions on cold start and then goes away.
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The GENIII engines are known for a cold start piston slap, although it is possible to have a lifter problem that presents itself when cold until it pumps up, and then becomes a more permanent issue as it gets older and wears out. Easiest way to determine if it's a piston or lifter noise is the speed of the noise (which can be hard to determine to an untrained ear). If the noise is the same speed as the crankshaft, it's in the bottom end, but if it's half the speed as the crank, it's in the valvetrain. If you have a timing light, you can bring the engine up to TDC and make a mark on the balancer pulley that's on top where you can see it, then start the engine and see if the noise is consistent with the speed of the timing mark while using the timing light. If so, the noise is bottom end. If you determine that the noise is from the rotating assy, you can short cylinders (remove spark or fuel one at a time), to see if the noise goes away. If it does, you have a rod knock, if the noise remains, it is more than likely a piston rocking in the cylinder (piston slap)
Last edited by budhayes3; 04-30-2011 at 05:44 PM.
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The GENIII engines are known for a cold start piston slap, although it is possible to have a lifter problem that presents itself when cold until it pumps up, and then becomes a more permanent issue as it gets older and wears out. Easiest way to determine if it's a piston or lifter noise is the speed of the noise (which can be hard to determine to an untrained ear). If the noise is the same speed as the crankshaft, it's in the bottom end, but if it's twice the speed as the crank, it's in the valvetrain. If you have a timing light, you can bring the engine up to TDC and make a mark on the balancer pulley that's on top where you can see it, then start the engine and see if the noise is consistent with the speed of the timing mark while using the timing light. If so, the noise is bottom end. If you determine that the noise is from the rotating assy, you can short cylinders (remove spark or fuel one at a time), to see if the noise goes away. If it does, you have a rod knock, if the noise remains, it is more than likely a piston rocking in the cylinder (piston slap)
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If you determine that the noise is from the rotating assy, you can short cylinders (remove spark or fuel one at a time), to see if the noise goes away. If it does, you have a rod knock, if the noise remains, it is more than likely a piston rocking in the cylinder (piston slap)
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Backwards Billy. Camshaft speed is 1/2 of crankshaft speed. Faster noise would be crankshaft speed, slower noise would be cam/valvetrain noise.
To help answer the other question, if you remove spark from a noisy cylinder, the combustion process doesn't occur. Since there isn't an explosion in the cylinder, there isn't a load on the piston & rod. Therefore, the noise gets quieter or goes away.
To help answer the other question, if you remove spark from a noisy cylinder, the combustion process doesn't occur. Since there isn't an explosion in the cylinder, there isn't a load on the piston & rod. Therefore, the noise gets quieter or goes away.
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Backwards Billy. Camshaft speed is 1/2 of crankshaft speed. Faster noise would be crankshaft speed, slower noise would be cam/valvetrain noise.
To help answer the other question, if you remove spark from a noisy cylinder, the combustion process doesn't occur. Since there isn't an explosion in the cylinder, there isn't a load on the piston & rod. Therefore, the noise gets quieter or goes away.
To help answer the other question, if you remove spark from a noisy cylinder, the combustion process doesn't occur. Since there isn't an explosion in the cylinder, there isn't a load on the piston & rod. Therefore, the noise gets quieter or goes away.
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#8
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But the compression proccess still occurs and the combustion process on the opposite cylinder firing at the same time still occurs hence still putting a load on the rod, wrist pin, and piston although it is less of a load, if there were a bottom end problem it would still make noise.
If you take away the spark, the air/fuel mixture does not ignite. It just goes thru the cylinder. There is no explosion to force the piston back down, there is no load on that cylinder.
And, only one cylinder fires at a time.
Trust me, this does work. I've been doing this stuff for a long time.