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Vince
03-19-2012, 07:35 PM
I am struggling to figure out root cause on a slight tapping noise on my TR3A. The engine had not been run for over 30 years until last year. It has great compression and oil pressure, runs very strong. But under load, at about 2500 rpm and higher, it makes a slight tapping noise. You can make the sound come/go purely with throttle position while driving. We were able to re-create the sound while sitting still if you rev the engine quickly, it will make the sound as it ramps up in rpm. Then a friend listened with stethoscope, determined it was cylinder #3, we unplugged that cylinder and the tap went away. Thought maybe it was excessive carbon buildup, looked like a lot of carbon thru the plug hole. Tried Sea Foam spray in plug hole, soaked overnight, then sprayed through carbs - lots of smoke but when done it still makes the slight tapping noise.

Have already made mixture richer, checked timing, and switched to 92 octane fuel. None of these seem to really make a difference. Rocker clearances all look fine.

Any other ideas?

M_Pied_Lourd
03-19-2012, 07:54 PM
Timing Chain?

Cheers,
M. Pied Lourd

NutmegCT
03-19-2012, 08:19 PM
Vince - if it's a *slight* tapping noise, which changes with rpm, I think it's perfectly normal.

Many guys here report something similar - which is just how the valves sound when normal.

Anyway, mine has the slight tapping noise; has had it since new. At first I worried; then a long-time TR owner said it's the way it's supposed to sound.

Tom

TR3driver
03-19-2012, 08:36 PM
The "normal" noises are from the valve train, and don't change with throttle position. They also aren't specific to one cylinder (although a bad rocker or valve might be). Since Vince's noise does change with throttle position, it has to be something that "sees" engine load.

My guess from the description would be piston slap, or (more likely) a loose wrist pin (aka gudgeon pin). Might not be anything to worry about, but if it starts getting louder, those are the things I would look at.

It's not a lot of fun to pull a rod out on a 3A, but at least it can be done without removing the engine or front apron.

BillyB62
03-19-2012, 08:39 PM
Thanks Tom, I pulled my car out of the garage this weekend (winter is almost over in New England, although it never really came) and ran it for a little bit. I just bought the car over the winter and I'm readying it for registration. The slight tapping concerned me but to hear it is normal is comforting. I'll let some of the other local TR3 owners in the state listen when I begin going to shows .

bgbassplyr
03-19-2012, 09:45 PM
Randall beat me to it,but I agree with him.....wrist pin.....or piston slap.

TimK1955tr2
03-20-2012, 06:13 AM
Last summer I had a loud tapping/clacking sound that appeared like it was coming the top end/valve train, it sounded very serious.

But it was just the Woodruff key that mounts the water pump pulley to its shaft being badly worn, allowing the pulley to tap against the housing or pump mounting bolts. I was able to rock the pulley on the shaft with the engine off but didn't notice any movement with the engine running.

Installing new key (found at sears), solved the problem and noise.

Kind of a long shot but worth a look... good luck!!

CJD
03-20-2012, 06:25 AM
Could also be an exhaust leak around the manifold...

John

Vince
03-20-2012, 12:17 PM
John, the exhaust leak occurred to me too recently. Seems to line up better with the symptoms. Any ideas on how to confirm? Of course, it's not that hard to replace the manifold gasket......

EV2239
03-20-2012, 04:46 PM
It could be a big end or crank problem because both will make a noise as you describe.

Oil pressure should be 70 at 2000 rpm and tick over at over thirty.

I'd drop the sump and have a look at the state of the journals.

CJD
03-20-2012, 05:37 PM
I wish I could say I have a good trick to tell a leak, but I really don't. Normally you can run your hand around to feel it blowing, but that's not very easy with the exhaust and intake in the same plane on the TR3!?! An exhaust leak is always sharper, or more piercing, sounding when the engine is cold. It also tends to go away when the engine is not under load. The only thing I can add is that it would be very obvious once you pull the gasket, and it's much easier than pulling heads, pans, or rods.


John

NutmegCT
03-20-2012, 06:01 PM
Vince - just a suggestion ...

Could you make a short audio and/or video so we can actually hear that sound? Maybe upload it to YouTube?

If you need help in doing that, just let us know.

Thanks.
Tom

TR3driver
03-20-2012, 06:06 PM
Any ideas on how to confirm?
Pour something into the intake that causes lots of exhaust smoke, like Casite or Rislone. Even ATF would probably do. Be careful though, don't want to pour in too much! Then look for any wisps of smoke coming away from the exhaust manifold area.

JFeher
03-21-2012, 07:23 PM
Have someone hold a towel or rag temporarily over the tailpipe at idle while you listen for leaks. This will pressurize the exaust and magnify any leaks.

Guest
03-21-2012, 07:47 PM
Randall beat me to it,but I agree with him.....wrist pin.....or piston slap.

X3

Vince
03-24-2012, 05:15 PM
Today I went to a friend's house and we adjusted the timing, ended up removing about 95% of the sound. So I believe it was detonation. Still curious why it seems to dominant on cylinder #3. But the engine seems to run fine with the timing retarded back.

I also found out when I replaced the timing chain and tensioner I put the lower pulley back on wrong, apparently. The timing mark on the pulley is off 180 degrees. But if you put your timing light on cylinder #3 then you can set the timing just fine.

Btw, my older manuals don't give good data on where to set the timing when using a light, and with my conversion to Pertronix I can't do the 12 volt bulb thing. We set it about 2 degrees before TDC (about 1/8 inch from mark), was at about 12 degrees when detonating (about 5/8 inch). Does anyone know where the timing "should" be with a timing light? Not that I'll change it because it seems to be running pretty darn good now.

Vince

Geo Hahn
03-24-2012, 06:21 PM
... if you put your timing light on cylinder #3 then you can set the timing just fine...

That should have some future owner saying a few choice words about you.

I have never used Pertonix but one way to set timing with a light it to set total timing (high RPM) where you want it and let idle timing be whatever it is.

CJD
03-25-2012, 08:06 AM
Glad it was something easy for a change. I am never that lucky!

John