Tapping Sound Question

[msova]

74 Spider

Tappet or Exhaust leak...or eff'd up valve????.....

How 'loose" (too much clearance) does a tappet have to be to start tapping? I've got a pretty broad range of clearances on my intake side (.16, .20, .16, .13) and wondering if this could be the cause of a tapping. Tappet "tapping" seems like it would sound "looser" if that makes sense. This tapping is very rythmic and "tight" sounding. Some of those clearances are "tighht"....could that be the cause?

On the exhasut side I have .19, .17, .19, .17. FWIW, the head that is now on the car came off a "supposed known good" spare engine (i.e.- I bought it off someone...was supposedly rebuild about 10K miles prior). I could not afford to have head work done at the time of a head gasket failure about a year ago, so I removed the spare head and it looked pretty good compared to mine. Tapping sound has been present since.

I've heard that an exhaust leak at manifold can cause a tapping sound. Pretty certain the manifold to head and manifold to downpipe are free from any possible leaks. If anywhere...I suspect the downpipe...specifically the area where the two pipes meet is really rusted. Or where the transmission to centerpipe mount is. Is it possible for a pinhole leak in these areas to cause a tapping sound or would it be more of a typical exhaust leak sound?

Is it possible for a valve or tappet to be sticking or bent or something...in other words...something more serious that allows the engine to still run ok? (engine runs good but feels a little different than I remember)

Marc

[kilrwail]

I won't try to comment on your various clearances and I've never heard of an exhaust leak causing tapping. But, you could probably isolate the location by using either a really long screwdriver or better yet, a broom handle, as a stethoscope. Place one end where you suspect the noise may be originating and the other end in your ear (well, tight against your ear, anyway). You will either hear the tapping very clearly, or just the normal sound you'd expect in that place.

[mbouse]

the exhaust leak tapping sound is very annoying, especially after a freshly installed head-job.

exhaust manifold to down pipe on my '80 is fully tightened with a new gasket, but there is just enough gap there to cause this annoying sound. ONE DAY, i will get around to fixing that leak.

it took a great deal of time to find the source of the noise because i wasn't looking for a leak. my leak is significantly larger than a pinhole, but not large enough to be an immediate concern. even with the hood up, all i hear is the tapping. gotta have my hand within 1-2" of the gap to even determine that the leak exists.

Do you have an exhaust leak? if you can find a leak, i'd suspect it would be the source of the tapping sound.

[msova]

is there a good way to determine a leak?...some magic colored smoke or some other wizardry???? Maybe turn on the gas of a butane torch and see if it ignites from hot escaping gases? lol... I'm reaching here....

I took it to a muffler shop and the guy didn't even seem to want to inspect for a leak since he just assumed it was the engine

[kilrwail]

Get a good cigar going well and fill the engine compartment with smoke You should find the leak and it will smell really cool in there for weeks.

[msova]

Used to smoke cigars a bit...haven't for some time. I'll have to get me a nice dark honduran fatty.

So will I see the smoke being pushed away from the area of the leak, if there is one?.....provided the rad. fan is not on at the time.

[kilrwail]

That's my theory, but I've never tried it. It's a good excuse for a good cigar though

[racydave]

I use a stethescope with only the open tube for exhaust noises. And you will not burn your fingers!

[So Cal Mark]

for an exhaust leak to sound like a tick, it has to be right at the manifold/head flange

[msova]

Thanks Mark....that's what I was wondering (whether it had to be at the manifold in order to make the sound).

hmmmm.....could be that the ex. manfld. mating surface on this head is not perfect. Didn't think of that one. I had the ex. manifold surfaced when I swapped heads...but since this head was from a different motor....crapola!

If I find a leak here....think I can try to seal it up with some red rtv or ultra copper? I know its not a perfect fix....but at least something temporary. Will try the cigar technique this weekend...supposed to be a bit warm on sat.

Otherwise....its back to the tappets.

[ventura ace]

Marc,
You should even out the intake clearances, regardless. I'd leave the 16's as is, and try to get the other 2 somewhere close like 16 or 17.

Alvon