Car developed a new tapping sound recently. The sound persists through all RPM, serpentine belt was also removed with the sound persisting. Initially heard a few chirps/squeaks randomly while idling after startup. I thought it was just the belt going. After a few km, the engine now sounds like this cold/warm.
- No new mods recently
- The Sound "seems" to be coming closer to 1 & 3 cylinders on the drivers side but it's hard to pinpoint.
- No apparent loss in power or oil pressure.
- Headers have had no leaks for years (locking header bolts).
- Engine was rebuilt 10 years ago with not a lot of mileage since and no other issues.

Hoping for someone to jump in and say this doesn't sound like an early sign of a spun bearing/rod issue ... hoping it's just a valve issue or exhaust leak. Right now I'm leaning towards an exhaust leak at one of the manifold bolts .

 

Sounds like rushing air to me. I’d be looking for exhaust leaks and maybe also vacuum leaks.

Could be something like a rocker, too — couldn’t hurt to pop the valve cover and check it out.

 

I've never had good results listening to these videos, and I use my high end Sennheiser headphones. Sounds like valve train to me. Are you using a stethoscope to try and pinpoint the noise in the #1/#3 area?

 

Thanks Jake/Injuneer. In person I can just make out a very hard to tell higher pitched "PPfsh" sound that sounds almost like tapping (but not quite), so on one side I'm leaning towards exhaust leak - but with locking bolts and no problems with the headers for years my brain doesn't want to believe it.

I don't have a stethoscope, I ordered a decent one about an hour ago.. should be here in a couple of days (should have bought one ages ago!).

For now I'm going to go hunting for the exhaust leak, is a spray bottle with soapy water on a running cold engine very effective? Based on the rate of the tapping sound, is it safe to assume a leak would be at one of the exhaust manifold ports by the block? I would imagine leaks further down the line would have a faster temp from all of the cylinders hitting it.

*crosses fingers for an easy fix*

Update - spray bottle was a fail, headers got way too hot too fast Listening to the engine from a few different angles, the sound seems more internal... even though its louder on the drivers side its still very noticeable from the passenger side, I would expect an exhaust leak sound to be blocked by the block much more... No obvious signs of a leak either from the headers that I could tell.

 

At first it sounds like lifter clatter, then later more like an exhaust leak from the passenger header.

 

Thanks all for the feedback so far!

I wasn't able to find a header leak with the stethoscope directional sound adapter, sounds more internal when I use the mechanical adapter on the scope (valve covers were on). Using the scope it absolutly seems to be more clear/louder on the drivers side, oddly by exhaust port, but internal sounding. Best I can tell is that it is the #7 cylinder. I haven't had time to do a proper inspection job yet, so will do a 2nd round with the scope more carefully and the see if i can find anything out from under the car (praying for an exhaust leak) very soon. I'm going to remove the valve covers this time too and throw up some cardboard for oil spillage.

I've yet to do anything with the top end of the engine and so am researching the best i can on what to look at and inspect.

Here is what I've got planned so far, please step in and set me straight if I'm missing something, being overly cautious or "doing it wrong" .

• Remove Valve Covers
• Check stock rockers for any obvious excessive play/clatter, visual inspection across springs/pushrod position.
• Bring Engine to #1 TDC (#1 valves should be up/closed and piston should be extended in cylinder) - Arrow on engine hub should be pointing straight up (12 o'clock)
  • Check Intake Valves on 1, 2, 5, 7. Exhaust on 1, 3, 4, 8 (god bless your page shoebox! Method 1)
    • Visually inspect Spring (Not sure what to look for unless catastrophic failure?)
    • Any Clacking Rocker Movement up/down, being careful not to compress the lifter.
    • Roll the pushrod to see if bent, dragging unevenly.
    • Double check pushrod for any up/down play, being careful not to compress the lifter
    • If loose, press down on the rod to see if the lifter has "spring" to it still.
    • Would anyone recommend I just loosen the rockers and Zero lash +1/2 turn the I/E valves at this point if nothing wrong is found? (or is if it ain't broke don't fix it)
• Rotate 360°, Repeat above Checks on Intake on 3,5,6,8, Exhaust on 2,5,6,7

Is the above OK to do with the intake manifold still on? I was hoping to only take the intake off if I have a symptom which leads me to needing to do it... i.e. play in the pushrod and no spring to the lifter when i press down on the rod.

I was considering doing an engine running adjustment, but am I correct to assume that If the lifter is collapsed I may temporarily solve/improve the ticking at the expense of more serious damage to the valvetrain "soon" from not addressing the root cause?

 

Heed Shoebox’s caution about the crank hub being in the correct orientation. The hub is not keyed to the crankshaft, it is remotely possible it moved. Or if someone removed and replaced it, it could be anywhere. To check, as the #1 piston approaches TDC on the compression stroke, you should feel pressure build with your finger over the spark plug hole.

With regard to a possible exhaust gasket leak, a leak will often leave a carbon track on the adjacent surfaces. Use an inspection mirror to check the surface of the heads below the manifold to head gasket.

 

Thanks for the words of warning! I've managed to isolate the sound with the Drivers valve cover off.

The sound is coming from the #7 Intake rocker/area. Using the scope it definitely loudest coming exactly from the middle of the rocker, not the pushrod and not the the top of the spring.

Additional info/what i did next:

• The car still has stamped rockers, no real issues with the other rockers that i noticed. Plenty of oil ...
• With the valve closed i could turn the pushrod between my fingers with some effort, it definitely was not loose at all. (Not sure if this is good/bad/normal, i know loose would have been bad)
• It sounds more like a metal squeeky sound, not a tapping sound
• I backed the rocker nut while running and the sound went away as soon as the rod's started to begin tapping.
• Tightening the nut a tad got rid of the tapping but brought back the problem sound (more squeeking).
• I relaxed the nut a tad till the problem/squeek sound went away, the tapping just barely came back
• I shut the engine off and with the rocker nut still loosened and the valve closed.
• I was able to freely spin the pushrod, and there was some play now that the nut was loose.
• I couldn't feel any spring /give in the lifter when pushing the pushrod down. How much force is needed? I'm wondering if a seized lifter is the root cause?

I think the next logical step is to take the rocker off next, but I'm not sure what to look for. I'll post a pic in a bit...

 

 

In the second paragraph of SHOEBOX’S procedure, he notes the lifter will bleed down after you find zero lash. Take a look at that and see if it helps. That would suggest that the lifter will continue to bleed down. I can’t relate directly to your question, because I run solid roller lifters, and full roller rockers. That rust looks out of place..

 

Thanks Injuneer, hopefully someone else can chime in. This is very good news if it's just a failed rocker - but I'm more worried about why it failed (there was plenty of oil). I'm now thinking when the engine was rebuilt years ago they reused the rockers so these might have over 160 000+ miles on them.

As much as I want an excuse to go heads/cam/rockers ... this year is not the year for me to do it! ;D Hoping i can throw a new stock one back on and buy a bit of time to do things right!

 

The sound is coming from the #7 Intake rocker/area. Using the scope it definitely loudest coming exactly from the middle of the rocker, not the pushrod and not the the top of the spring.


Okay, so you have isolated the sound to the No.7 intake rocker, and, of course, you still have the driver's side valve cover off, right?

Do this .... remove that "squeaky" No.7 intake rocker arm and pivot ball as an assembly, (i.e. keep the rocker and ball together!), then ...... also remove the No.1 intake rocker and ball, again as an assembly ...... and switch them!

If the "squeak" follows the rocker assembly .... just replace that rocker and ball. But, if the "squeak" continues at the No.7 intake position, even after switching to a different rocker assembly ....... you have a bent or partially pulled rocker arm STUD that needs replacement/service, if you're "lucky". Or possibly much worse, a bent push-rod, collapsed lifter, etc., etc..

And, of course, Good Luck!

 

Thank you for the tip! Unfortunately the ball and rocker have already been separated when i inspected them So it may "go away" with the repositioning on the new rocker, but at least if it stays with the stud I know something else is up.

I did manage to check the pushrod on some tempered glass, it rolled no problem and the passage is clear. The car was running smooth aside from the noise. I noticed nothing until a "chirp/squeak" happened on startup one day, it came and went for a few seconds, then came back permanently after a short drive. Also the sound managed to stop when the lifter was loosened so this means it's likely not major bearing going (whew!) Given the above I'm optimistic this is really just the rocker arm! I would expect worse if a lifter collapsed.

FYI there is a very faint scour mark on the ball nut, I'm guessing it's probably bad.

 

@shoebox @Injuneer Thanks for the heads up regarding the Hub/Pulley not being keyed. "Turns" out mine was off by 180°. The good news is I managed to swap the bad Intake rocker with the good exhaust rocker on #7 with no issues (thanks @97 6SPEED Z for the tip). The bad news is the sound stayed with the #7 Intake right at the stud/rocker. I confirmed with the stethoscope, its 100% for sure loudest there. I'm crossing my fingers it's just a bad Stud, but it does seem like a really odd failure point to me

I found this video, which sounds too similar to mine (in person using the scope, oddly the chirp doesn't pickup as well on my mic). End result was a damaged lifter and trashed cam: https://www.camaroz28.com/forums/lt1...squeak-867779/
In my case, if it is a lifter I'm still wondering how sound would travel right to the #7 intake rocker stud, wouldn't the lifter have to transmit the sound through the pushrod to the rocker, making the pushrod end louder?

I'll post an update when I replace the stud - hoping for the best, preparing for the worst. If anyone knows the stud replacement process on these heads off the top of their head feel free to chime in..

 

It has been a loooooong time since I've had stock cylinder heads on my car, but, if memory serves after you've removed the rocker arm nut, rocker and pivot ball, here's the procedure for removing the stud:

On the stock aluminum F-Body LT1 cylinder head, the rocker stud is a "screw in" type stud. The stock 3/8" diameter stud is removed by using either a 5/8" (English?) or 16mm (metric?) deep well socket, and just unscrewing the hex at the base of the stud.

On the stock head, the threaded hole that the intake stud screws into should be a blind hole. But, if you've had any porting work done, the intake stud hole may extend into the intake port. If the intake hole is blind, just lightly oil the new stud with engine oil and torque it to 50 ft-lbs. But, if the stud hole is now a through hole into the intake port .... the threads on the replacement stud MUST coated with thread sealer, before (again) torquing to 50 ft-lbs.

And again .... Good Luck!