I think there is a tap dancer in my hood

[DissFigured]

I suspect that Michael Flatley has left the river dance, and works inside my Mustang now.


Why do I hear a tapping sound: I hear it when I am accelerating. There is no tapping when I idle, or when I maintain speed. It only does it under strain. If I am in Neutral nd I rev the engine, I do not hear any tapping. It's only when driving.

I have ruled out a Manifold leak by putting a bit of transmission fluid in the carb and verifying that smoke only came out of the exhaust rather than in the engine compartment.(this was advice I got from the Motor Men on a local radio station)

So, how do I determine the cause of the tapping, and how to I resolve whatever the potential issue might be? For example, someone told me it might be a dead lifter. If that is the case, how do I confirm it and how tdo I fix it.

someone told me to put in some wizard mystery oil something or other. that seems to have had no effect.

This just started yesterday by the way.

 

[66stangbluework]

when the tapping happens does it feel like youve lost alot of power? It might be a valve that needs to be tightened, but that would make a sound in neutral me thinks Gotta love these fords

 

[DissFigured]

I do feel like it has less power. Initially, I thought maybe a spark plug was bad because it didn;t feel like I had all my power. I haven;t verified that the plugs are good or bad as they appear to be a pain in the ass to remove.

 

[66Runt]

some simple checks

First check your oil level. If it is too high it can cause the lifters to starve of oil, as well as cause some other weird noises. While in there check your motor mounts and the bolts.

Next put a vacuum gauge on the car. If it is a valve problem the needle will vibrate with the speed of the tapping.

If the tapping stays consistent with the engine rpm, I would try a stall test to confirm the noise is coming from the engine and not the flexplate/torque converter. Or a loose motor mount rubber that allows the fan to hit something under load.

Piston wrist pins being loose will cause a very similar noise. Normally this will sound just a slight bit softer (like hitting the head of a drum versus the rim) and slightly more baritone than a lifter, but is often confused with lifters.

If you still have dificulty isolating the problem, go to a garage with a dyno, where they can strap down you vehicle and put it under load, while listening for the tapping.

Hope you find it is something cheap and simple!

Scott

 

[krash kendall]

Your timing is too far advanced. The engine is pinging under acceleration.

Pouring tranny fluid down the carb to find a vacuum leak? Were they serious? There are so many things wrong with that, but the obvious is that a manifold leak is a vacuum leak, so smoke wouldn't come out of it even if it were 1/2 an inch wide. Spray WD40 or something else flammable at the manifold and carb base to check for leaks. If the RPM goes up you have a leak.

 

[John Z]

Your timing is too far advanced. The engine is pinging under acceleration.

Pouring tranny fluid down the carb to find a vacuum leak? Were they serious? There are so many things wrong with that, but the obvious is that a manifold leak is a vacuum leak, so smoke wouldn't come out of it even if it were 1/2 an inch wide. Spray WD40 or something else flammable at the manifold and carb base to check for leaks. If the RPM goes up you have a leak.

I'm guessing that this suggestion was to see if the exhaust manifold is leaking, not a vacuum leak. An exhaust manifold leak can sound like valves needing adjusting. I agree that since the sound only occurs under load that it is more likely pinging.

 

[krash kendall]

Exhaust manifold. Check! Still question pouring tranny fluid down the carb though.

 

[DissFigured]

so lets say my timing is too far advanced. The engine is pinging under acceleration.

What do I do? How can I check to see if this is the case, and how do I correct it once confirmed? Is this better left to a pro to fix?

 

[John Z]

so lets say my timing is too far advanced. The engine is pinging under acceleration.

What do I do? How can I check to see if this is the case, and how do I correct it once confirmed? Is this better left to a pro to fix?

To adjust your timing you loosen the clamp bolt at the base of the distributor then rotate the distributor. Originally you would set the timing using a timing light connected to the #1 spark plug wire and shining at the marks on the harmonic balancer. It can also be adjusted by ear or by using a vacuum gauge, if you have experience. It is relatively easy, but you may want someone to show you the process, since your question makes it sound like you do not have much experience. Do you have a mustang repair book?

 

[krash kendall]

Well for starters, you need a timing light to actually check it. If you want a quick fix, loosen the distributor hold down bolt and rotate the distrubutor counter-clockwise a couple of degrees to retard the spark slightly then take it out for a drive and see what results you have.

 

[DissFigured]

OK, I swivled my distributer cap all over the place and was able to actually create the sound some of you thought it might be but no dice.

I think it is something else. If I had a bad spark plug would I hear any noise?

Maybe tapping is not the best way to describe it. The clsest description I can some to to describe the sound is an air rifle (bb gun type thing) with no bb. just the puff of air. it seems perfectly timed with the pulsing of the motor

123 pop
223 pop
323 pop
423 pop

that leads me to believe it has something to do with one of the cylinders.
And again, I can gun it in neutral and hear nothing. Additionally if I accellerate ad a slow rate of increase I don't hear it. It is only when the engine is stressed arounf 3000 rpm.


Any other ideas?

 

[2nd Mustang]

I haven;t verified that the plugs are good or bad as they appear to be a pain in the ass to remove.

You are talking about an early Mustang, right? If you are, you are kidding, right? Ever try a front wheel drive V6?

 

[shotsy]

351C stuffed in a 70 is fun, I have to jack the motor still better than the front wheel drive chevy celeb, I dont thing the bit%h plug in the back ever got changed, check for a loose/missing plug if it sounds like an air gun going off under the hood

 

[DissFigured]

Drum Roll................



Loose Header bolts.
After trying everything, ai noticed the header bolts were really loose.
I tightened em. Now it sounds perfect.



Thanks for all the suggestions!

 

[D.Hearne]

Drum Roll................



Loose Header bolts.
After trying everything, ai noticed the header bolts were really loose.
I tightened em. Now it sounds perfect.



Thanks for all the suggestions!

I'm glad you figured this out on your own. I was about to unload on you. ( it can't be the plugs, cause they're too hard to remove?) Then Krash tells you to rotate the distributor a COUPLE degrees , not a few hundred, then you also decide that's not it. OH, and keep that wrench handy, those header bolts are going to be loose again. :damnit: