Intermittent valve tap

[ChrycoDUDE]

....or what sounds like valve tap. Last year I had to install new lifters and cam as one of the lifters on #6 collapsed. The engine would make that oh so familiar tap, tap, tap sound before I did the swap. Once I finished that it was all quiet again.
Now a few weeks ago coming home from a car show I started hearing that sound again, but it comes and goes...not steady with engine rpms...and it goes away completely when idling. I pulled the valve cover on that side to check the rocker arms...(with a collapsed lifter one can actually rock or move the lifter arm with fingers a tiny bit...that's how I find the bad lifter the last time). This time all the arms are nice and tight...can't be moved at all.

So kinda baffled here....anyone care to take a guess? I can start the motor right now and all will sound normal. Yet after five or six mins on the road the tapping will come back.

 

[PurpleBeeper]

Off the top of my head.....
1. Try to use Motor Medic (or similar) engine flush FOLLOW DIRECTIONS EXACTLY and change the oil. Maybe some "schmutz" got into one of the hydraulic lifter oil holes.
2. Put a mechanical oil pressure gage on it to be SURE you don't have low oil pressure.
3. Put on a new oil pump & check the oil pump/distributor gear for wear and replace it too if necessary..... it's cheap & really easy on a big block.
4. "Maybe" you actually have a small exhaust manifold leak that only shows up after the engine is warmed up (head/manifold OR donut gasket)? I've been fooled by that myself before & thought I had a lifter issue.

 

[oldbee]

5. Loose rocker shaft
Just throwing another one out there.

 

[oldbee]

6. Rattling heat riser after warming up?

 

[Yatzee]

View attachment 446032 ....or what sounds like valve tap. Last year I had to install new lifters and cam as one of the lifters on #6 collapsed. The engine would make that oh so familiar tap, tap, tap sound before I did the swap. Once I finished that it was all quiet again.
Now a few weeks ago coming home from a car show I started hearing that sound again, but it comes and goes...not steady with engine rpms...and it goes away completely when idling. I pulled the valve cover on that side to check the rocker arms...(with a collapsed lifter one can actually rock or move the lifter arm with fingers a tiny bit...that's how I find the bad lifter the last time). This time all the arms are nice and tight...can't be moved at all.

So kinda baffled here....anyone care to take a guess? I can start the motor right now and all will sound normal. Yet after five or six mins on the road the tapping will come back.

What you're hearing could be any number of things depending on the overall condition of the engine. Likely suspects are worn lifter bores, rattling oil pump relief valve due to worn or broken spring, reduction of oil pressure when hot, floating lifters due to weak valve springs or maybe worn bearing knock. You indicate it only happens when it's hot so I'd think heat has something to do with it. And if heats the culprit, expansion of metal parts goes along with it. Are your rockers, shafts or valve pushrods worn. Are you even sure that's the source of the noise? More info is definitely required, what you did, what you didn't, oil weight etc. It also seems your noise is directly related to increase in engine RPM's. You could try heavier oil and see the overall effect on engine noise to determine if wear is the issue. Do it temporarily, then dump it and go back to your regular weight of oil. There is so much that could cause this, that, if heavier oil quiets things down at least you know increasing clearances from heat is the issue. That or spend hundreds of dollars on something that really doesn't effect overall performance. At least your rear seal's not leaking!

 

[ChrycoDUDE]

Off the top of my head.....
1. Try to use Motor Medic (or similar) engine flush FOLLOW DIRECTIONS EXACTLY and change the oil. Maybe some "schmutz" got into one of the hydraulic lifter oil holes.
2. Put a mechanical oil pressure gage on it to be SURE you don't have low oil pressure.
3. Put on a new oil pump & check the oil pump/distributor gear for wear and replace it too if necessary..... it's cheap & really easy on a big block.
4. "Maybe" you actually have a small exhaust manifold leak that only shows up after the engine is warmed up (head/manifold OR donut gasket)? I've been fooled by that myself before & thought I had a lifter issue.

1. Good idea. Thx
2. Yeh have had that tucked under the dash for years....don't like idiot lights.
3. I thought about throwing a brand new dist in when I swapped out cams...maybe I should have.
4. This could be true but I think its unlikely. I'm pretty familiar with exhaust gaskets leaks sounds (some of the nuts seem to back off the studs ever so little over time). Anyways I don't think its that...I wish it were though. Simple fix.

 

[ChrycoDUDE]

6. Rattling heat riser after warming up?

Had to deep six that part...some how the mechanism had jammed itself completely stuck....in the closed position of course. Afterwards I just put the manifold (sans heat riser) back on.

 

[ChrycoDUDE]

What you're hearing could be any number of things depending on the overall condition of the engine. Likely suspects are worn lifter bores, rattling oil pump relief valve due to worn or broken spring, reduction of oil pressure when hot, floating lifters due to weak valve springs or maybe worn bearing knock. You indicate it only happens when it's hot so I'd think heat has something to do with it. And if heats the culprit, expansion of metal parts goes along with it. Are your rockers, shafts or valve push rods worn. Are you even sure that's the source of the noise? More info is definitely required, what you did, what you didn't, oil weight etc. It also seems your noise is directly related to increase in engine RPM's. You could try heavier oil and see the overall effect on engine noise to determine if wear is the issue. Do it temporarily, then dump it and go back to your regular weight of oil. There is so much that could cause this, that, if heavier oil quiets things down at least you know increasing clearances from heat is the issue. That or spend hundreds of dollars on something that really doesn't effect overall performance. At least your rear seal's not leaking!

Agreed. This is a mostly "stock" 383. Nothing crazy, it has a carb/intake/cam upgrade. Most of the valve train parts are stock...but I replaced the lifters w/the cam....and double roller chain. I also had the heads off and cleaned up with new valves put in because the seats had deteriorated from the shitty unleaded water passing for gas these days (had hardened seats put in). I'm not getting any white smoke when we are rolling along (ok well just a bit on start up...the rings have no doubt seen their better days), but not burning much oil other than that. I first noticed the "tapping" sound when leaving a local classic car corral. There is a four way stop light in front of the location where all the classic cars a parked for people to look at. Light turned green and while I didn't nail it, I did give it enough gas to "move away with certain authority" from the intersection (haha)...it's the ritual after the show ends that everybody does. Anyway down the road I let off it a bit and that is when I first noticed the "tapping" noise. At the next light I put it in idle and the noise completely disappeared. I goosed the pedal just a bit while sitting there just to make sure it was not my imagination playing with me, and still no tapping. So light turns green we drive off, no tapping. This last for about ten minutes. I sped up a little to merge on 55 mph highway. Just as I get up to speed the tapping comes back. It was like this on and off all the way home until I parked it. I'm currently running 10w40 rated oil..and the motor has decent pressure...getting about 40/40+psi at idle, and changes upwards according to speed (ex: 60mph will read around or no less than 55psi or so). Nope. No real seal leaks, lol. Guess I should be thankful for that.

 

[PurpleBeeper]

So....what IS your oil pressure at idle? at 3000 rpm? If the pressure is good, then flush the engine & if the "tick" is still there, then "maybe" a half-spun #4 cam bearing? I believe the upper end oils through there. A PIA to change, but you wouldn't have to pull the motor.

 

[oldbee]

Kinda sounds like 'crap' in a lifter- Marvel mystery oil or similar should get rid of it.

 

[PurpleBeeper]

Kinda sounds like 'crap' in a lifter- Marvel mystery oil or similar should get rid of it.

"schmutz" up I a lifter would be my first guess too.

 

[threewood]

Just a shot in the dark but could it be a flex plate bolt coming in contact with the dust shield? I have had it happen at higher rpms but silent at idle.

 

[ChrycoDUDE]

Just a shot in the dark but could it be a flex plate bolt coming in contact with the dust shield? I have had it happen at higher rpms but silent at idle.

Bingo give that man a prize. Thought I'd have a look at that too and damned if that wasnt it.

 

[threewood]

Glad you figured it out!

 

[RF2]

Be very careful with motor flushes. If you don't get it all out it will eat up your bearings like this.

 

[Officer Higgins]

Just my opinion but i would be scared to use flush seems like it would loosen up alot of stuff to run through rest of engine.

 

[Johnpat]

With it running use a stethoscope & or broom stick with your ear on it & locate the noise first

 

[Officer Higgins]

Yep good advice he said flex plate bolt caused the noise

 

[Johnpat]

With it running use a stethoscope & or broom stick with your ear on it & locate the noise first

 

[TOMRR]

Maybe" you actually have a small exhaust manifold leak that only shows up after the engine is warmed up (head/manifold OR donut gasket)? I've been fooled by that myself before & thought I had a lifter issue.
This did happen to me, changed the exhaust pipes gasket and tap went away

Tom C.