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I cannot figure out the source of a tapping sound in my freshly built motor and it’s been driving me nuts. I’ve adjusted the valves 20 times 1/4 turn 3/4 turn everything. Had a collapsed lifter that I replaced still not fixed. Had an exhaust leak from loose bolts, tightened them and sounded like it mostly went away. But now it’s fairly loud and definitely sounds like a metal on metal tap. Lifters all have their retaining clips and rollers all spin nice and smooth with no damage. Roller rockers are all in good shape from what I can tell. I don’t know what else it could be. Timing chain is my next best guess but definitely sounds like it’s coming from the top of the motor towards the center of the intake. This isn’t the typical sewing machine noise I’ve had this motor for years definitely not normal.
I don’t know sounds a bit light to be a rod knock. I had a rod knock before rebuild and I think I remember more of a clunking sound. Also still have great oil pressure
The only RR that clear stock VC were the Crane, also GMPP, Gold Narrow Body ones. Anything else the VC drip baffles need trimming on intake side so if yours are not, look for any witness mark on them. Some did bend them away but most just cut them (pic), courtesy of Golen Engines
The covers are in fact cut already. I just pulled the intake yet again after I watched it run with the covers off. And saw the rocker that seemed to be following the tapping sound. It’s the single lifter I changed out recently. Pulled the lifter and looks pretty good to me. Only thing I noticed is the roller is clearly rubbing on side of the lifter body. So I’m think maybe the cam lobe has a slant and may be pushing the roller to the side every rotation? I find it hard to believe that could make that loud of a tap especially on a new lifter. But I can see the marks from it rubbing on the side of the roller and lifter body next to the roller. This lifter was swapped because the last one collapsed. Not sure if this would have anything to do with that
Replaced all lifters still tapping. Now moved to pulling the chain cover. Was hoping to find rubbing marks on the cover but it’s not that loose. Probably have 3/4-1 inch of side to side slop so it’s not the tightest. I used the old sprockets in the rebuild being impatient. Figuring I’d replaced it soon which I’m likely about to do. What’s the odds this is my tapping sound? Really out of ideas my next and probably final guess would be rockers or something with the oil pump drive. If none of them fix it I guess rods would be only option but I’ve had rod knock really doesn’t sound the same
You didn't happen to put in a new oil pan that needs the windage tray cut up to get the oil pump pickup tube to fit? If you don't carve that windage tray in accordance with the instructions, you will have lower engine tapping. Just please . . . don't ask me how I know this . . . but its solved now. That engine that is meant for my Catalina is perfect now.
Check the ends of the pushrods and rocker tips they are supposed to be shiny and smooth. If you have scratches/marred up I would replace them.
Also if this is a new engine, every time I have put new lifters in an engine they are always super loud to my ears until I go and beat on it, regardless of oil pressure.
It’s a stock oil pan. Have had the rockets and pushrods out a few times and looked them over nothing out of the ordinary. Motor is a 350 I just had bored 30 over
Listening to your video(before you rev it), watching the video timer, and using a mouse click counter to click with the sound....there are roughly 30 clicks in 5 seconds. Multiply that by 12(for rpm) and you get around 400 clicks per minute.....roughly 1/2 of the stock engine idle speed. I think the sound is a rocker or something with the valvetrain. Grab a mechanics stethoscope and you will be able to isolate it to the engine side and general area of the valve cover.
Edit: Just read your comments on listening to it with the covers off.
If you replaced the lifter, it's still doing it, and you are sure that it's the one making the noise....then I would start looking at the lifter bore and holes supplying oil to that lifter.
Another thing to try would be to move that lifter to another cylinder that is working fine. If the sound does not move, the lifter is not the problem and I would suspect oil supply to the lifter if the rocker adjustment is done correctly.
This gentleman is speaking on non roller hydraulic lifters, but I think how the check valve section works is the same. This may also give some additional food for thought.
All lifters are brand new only took one drive to see if it still made sound. Clogged oil holes to one or more lifters is something I’ve thought of. Not really sure how would address that
I had a loud tick once, hard to figure out, and and it turned out to be an exhaust leak between the header flange and the header tube where there was a small spot where the tube wasn't welded to the flange thoroughly, allowing a leak on the under side and one of the pipes near the back of the driver's side where its hard to get in there. I only found it after taking off the header and doing a close inspection. Easy to fix, hard to find.
Another time I found that the copper gaskets I was using weren't the correct port shape to seal completely on the bottom. They were LT1 copper gaskets, and I can't remember the brand name, but it wasn't something that I expected to find when I took them off and saw what was happening. They were all borderline along the bottom wheere the sealing edge was really thin.
06-04-2024, 06:57 PM
Unsolvable tapping sound 94 LT1 
