Maybe a wiped cam lobe?

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Maybe a wiped cam lobe?

Post by JF74chevelle on Tue Apr 11, 2017 11:45 am

I think I may have a wiped cam lobe but I'm am not entirely sure, I haven't removed the valve cover to check the rocker travel yet. There is definitely a ticking noise coming from valve train. The exhaust is popping more than usual, I have true dual exhaust so it pops and crackles when downshifting but it does it more now when I depress the clutch to shift and when revving the the motor just mildly. What would you guys check first. The CAm and lifters are not new. Thanks-Justin
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Re: Maybe a wiped cam lobe?

Post by clanceman427 on Tue Apr 11, 2017 2:34 pm

I believe you have an exhaust manifold (or header) leak. The increased popping/gurgling might be the oxygen getting let in thru the leak and helping re-ignite some of the unburnt fuel. I had this same scenario on my old buick and that's what it turned out to be. It was hard to diagnose until I saw that one of the exhaust manifold bolts had broken.

Some say you can take a tissue and hold it around the areas (carefully! use gloves) of the exhaust ports to tell if you have a leak, but of course you'd have to first remove the cooling fan and run the engine without it to try to isolate any leaking exhaust pulses.
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Re: Maybe a wiped cam lobe?

Post by JF74chevelle on Tue Apr 11, 2017 2:53 pm

clanceman427 wrote:I believe you have an exhaust manifold (or header) leak.  The increased popping/gurgling might be the oxygen getting let in thru the leak and helping re-ignite some of the unburnt fuel.  I had this same scenario on my old buick and that's what it turned out to be.  It was hard to diagnose until I saw that one of the exhaust manifold bolts had broken.

Some say you can take a tissue and hold it around the areas (carefully!  use gloves) of the exhaust ports to tell if you have a leak, but of course you'd have to first remove the cooling fan and run the engine without it to try to isolate any leaking exhaust pulses.
that was the first thing I checked but I'll definitely give it another look.
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Re: Maybe a wiped cam lobe?

Post by JF74chevelle on Tue Apr 11, 2017 7:26 pm

Turned out to be a gnarly exhaust leak, some how the very back bolt backed way out, tightened it up and no more noise
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Re: Maybe a wiped cam lobe?

Post by wbaker01 on Wed Apr 12, 2017 8:37 pm

In case you want to know...My big block lost a cam lobe/lifter a few years back. Car had an intermittent knock, backfire through exhaust from time to time and was down on power..

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Re: Maybe a wiped cam lobe?

Post by JF74chevelle on Wed Apr 12, 2017 8:48 pm

I'll use this at reference because I checked the valvetrain and everything was fine
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Re: Maybe a wiped cam lobe?

Post by pila on Wed Apr 12, 2017 10:27 pm

When I suspect a cam lobe going South, I remove & Cut the oil filter apart first. If there's any metal, it may be bad, but no metal.. Very Happy

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Re: Maybe a wiped cam lobe?

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