Maybe a wiped cam lobe?

by JF74chevelle 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

by clanceman427 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.

by JF74chevelle 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.

by JF74chevelle 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

by wbaker01 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..

by JF74chevelle Wed Apr 12, 2017 8:48 pm

I'll use this at reference because I checked the valvetrain and everything was fine

by pila 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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Maybe a wiped cam lobe?

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