Intermittent engine tick (with video)
05-28-2009, 12:39 AM
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Intermittent engine tick (with video) Short version:
01 Z28, H/C setup, LS7 lifters. Engine ate several lobes on the previous cam and took lifters (also LS7). 90 miles ago, the cam and lifters were swapped. The engine ran fine for about 80 of them, and now ticks/knocks intermittently. The noise is substantially worse after reaching operating temperature.
Cold start: http://www.youtube.com/watch?v=ZQfDGfF6X3g
Operating temp: http://www.youtube.com/watch?v=rHAlLjRAIlE
The rest of the story:
After the engine started ticking again, we checked the hardened pushrods, dual valve springs, all the rockers, the exhaust for any leaks, and the spark plugs. The #4 spark plug was fouled after being run ~70 miles, none of the other plugs looked bad. The engine had enough fuel, did not show any knock retard while being run hard, and was not running excessive timing at WOT. With exception to the fouled plug, everything we have checked so far has been okay.
The noise is inconsistent: it is worse when the engine is decelerating. At idle (hot or cold), the noise is sometimes not present. Driving shortly after cold start, the noise is very minimal. After reaching operating temperature, the noise is very prominent while driving.
While hot, the noise comes and goes while the car is stopped. It is much louder as the engine decelerates (returning from ~2k rpm to idle). It is not as noticeable as the engine accelerates.
Any ideas?
EDIT: Oil pressure has not changed, even after the knock developed. It is around 60psi at idle (hot/cold).
01 Z28, H/C setup, LS7 lifters. Engine ate several lobes on the previous cam and took lifters (also LS7). 90 miles ago, the cam and lifters were swapped. The engine ran fine for about 80 of them, and now ticks/knocks intermittently. The noise is substantially worse after reaching operating temperature.
Cold start: http://www.youtube.com/watch?v=ZQfDGfF6X3g
Operating temp: http://www.youtube.com/watch?v=rHAlLjRAIlE
The rest of the story:
After the engine started ticking again, we checked the hardened pushrods, dual valve springs, all the rockers, the exhaust for any leaks, and the spark plugs. The #4 spark plug was fouled after being run ~70 miles, none of the other plugs looked bad. The engine had enough fuel, did not show any knock retard while being run hard, and was not running excessive timing at WOT. With exception to the fouled plug, everything we have checked so far has been okay.
The noise is inconsistent: it is worse when the engine is decelerating. At idle (hot or cold), the noise is sometimes not present. Driving shortly after cold start, the noise is very minimal. After reaching operating temperature, the noise is very prominent while driving.
While hot, the noise comes and goes while the car is stopped. It is much louder as the engine decelerates (returning from ~2k rpm to idle). It is not as noticeable as the engine accelerates.
Any ideas?
EDIT: Oil pressure has not changed, even after the knock developed. It is around 60psi at idle (hot/cold).
Last edited by ryansm1; 05-28-2009 at 01:03 AM. Reason: Added information
05-28-2009, 12:46 AM
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man that first video sounded just like mine did when i had a spun rod bearing, a chirping sound is what it was, i never ran it enough to get it up to operating temp after it started doing it, but thats what mine sounded like! i tore it down and sure enough it was a rod..
05-28-2009, 01:01 AM
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man that first video sounded just like mine did when i had a spun rod bearing, a chirping sound is what it was, i never ran it enough to get it up to operating temp after it started doing it, but thats what mine sounded like! i tore it down and sure enough it was a rod..
I forgot to mention that oil pressure has not changed from the engine's pre-knocking state (holding ~60psi at idle).
05-29-2009, 01:10 AM
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mine didnt change much when mine was knocking too, change the oil (if you havent done so already) and make sure thats not what it is.. if it is a bearing there will be alot of metal flake in the oil, and alot of metal on the drain plug magnet. i didnt think mine was a knock at first cuz the oil pressure was still good, but it def was..
09-12-2009, 06:38 PM
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Sorry it has been awhile, but I haven't touched the car since Ryan posted this up, I am going to change the oil and start diagnosing the problem, any more help is greatly appreciated.
09-12-2009, 10:47 PM
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Well there are no metal shavings in the oil at all. I will cut the filter in half tommorow and see how it looks. Still not sure what the problem is though. I will start taking the top end apart tommorow as well.
