I noticed when I accelerated to around 50mph the rpm’s began to fluctuate. I’ve rode for about a week now. Considering I’ve installed a VS cam, 7.00 push rods, comp cam lifters an 3 gen m90. I don’t know what sounds are normal for my setup. I’m developing a level of paranoia. lol Now that the exhaust is back on it’s quiet enough for me to hear the motor. I’m hearing a loud tapping sound that sounds to be coming from the back of the engine. Today was the second time changing the oil an the tapping continues. I’ve parked it for now because I don’t want to make things worse. I’m unsure what can cause the fluctuating rpm’s an tapping sound.

 

I'd pull the rear VC and look at the valve train. Could be something as simple as a rocker bolt that wasn't torqued enough and is backing out or it could be a lifter that isn't pumping up right. Lifter failures are not uncommon, even new, and seems to happen OEM or aftermarket.

But with the VC off you can at least compare the parts for a few cylinders to each other to see if one looks different.

 

Thanks, when time allows I’ll check the valve train.

 

This morning I began to open the valve cover by starting to remove the rear spark plugs. I removed spark plug 2 first when I felt another spark plug dangling on the back of my hand as I removed the first plug. With my flash light I witness burn marks on the dangling spark plug which turned out to be plug 6. I suspected maybe that could have caused the tapping sound I was hearing so I plugged the two plugs back up an the tapping was gone. The tapping struck me as weird in the first place because I didn’t recall it tapping after the swap. I also reviewed videos an didn’t hear any tapping. When I noticed the tapping seemed to be shortly after it started ticking. Now I have to figure out why the rpm’s fluctuate at 50mph.

 

Lucky it was an easy fix at least!

 

True, indeed!

 

That "tapping" and plug issue you mentioned. Years ago on a 3100 powered grand am, I change spark plugs and had a problem that the last owner had a plug over torqued in the head. It broke during removal and took an easy out to remove it. I forget how long after having the new plugs, I heard a tapping. Found that plug not torqued (when the engine was idling and I was inspecting, I had a plug wire shaking way more than any other and lead me to that plug), so I tightened it up. Third time it happened, turns out, it barely had any threads in the head. End result to that mess was a heli-coil. BUT, point was a loose plug can make a tapping.

 

That’s something, that’s really cool. I never heard of heli-coil. That’s good to know heads can be saved in such a case. Thanks for the reassurance about the tapping. So far I haven’t heard anymore tapping since the incident.

 

When I did it, I bought a kit called Save-A-Thread. Might be a different name now. But it specially talked about spark plugs. Technically you are to do it with the head off the block. I made sure the tap was oiled, go part way, remove it, clean shavings, re-oil and repeat. Also, got a skinny tube and adapted it to the shop vac and ran it down the plug hole into the cylinder for extra measure. After doing that, NEVER had a problem again on that car. Never had to do it since.

 

Thanks, that’s informative. Props for the extra measures. That’s cool things worked out so well.