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Porsche 912 - Engine tapping noise, what could it be?
Posted: Fri Jun 24, 2016 4:03 pm
by tjbates
Hello,
I am trying to get to the bottom of what this noise could be?
https://youtu.be/gEYKqjbyPMw
You can hear it between 0:10sec - 0:14sec.
My Porsche 912 runs great except it has this 'tapping' noise during acceleration whilst under load.
I've checked the compression, timing (28degrees @ 3500RPM), valve gaps, float levels on my Solex 40s.....
Could it be a knock/ping, associated to lean mixture? I'm no mechanic and would really appreciate some guidance.
Thanks.
Tom
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Sat Jun 25, 2016 10:25 am
by neilbardsley
Does occur when accelerating or slowing or all the time? How about if the car isn't moving and you rev the engine?
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Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Sun Jun 26, 2016 11:05 am
by tjbates
Hi Neil,
It only occurs when the engine is under load during acceleration.
I can rev the engine without a problem whist the car is stationary. During declaration I get a slight burble/backfire (which I think is normal?).
Tom
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Sun Jun 26, 2016 12:15 pm
by Nige
Difficult to tell, sure it's not the gearshift linkage or something rattling as the drivetrain moves under load? Essentially are you sure the noise is from the engine.
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Sun Jun 26, 2016 12:22 pm
by cubist
Backfire? Lose silencer jointing or heat exchanger? Rock the tips up and down for excessive movement... when it's cold.
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Sun Jun 26, 2016 3:52 pm
by neilbardsley
What max advance do you have?
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Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Mon Jun 27, 2016 6:46 pm
by Winston Teague
Leaking exhaust flange gasket?
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Mon Jun 27, 2016 8:22 pm
by cubist
This ^^^^^^^^
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Mon Jun 27, 2016 9:05 pm
by tjbates
Nige, i'm pretty confidant it's from the engine as I've ran with 2 different transmissions (4-speed & 5-speed) and the noise is there with both.
Cubist & Winston Teague, i'll check my flange gasket. I'm not sure why i find the word flange funny
Neil, i've got 28 degrees at 3500+ RPM...
Re: Porsche 912 - Engine tapping noise, what could it be?
Posted: Wed Jun 29, 2016 9:08 pm
by Winston Teague
[quote][
Cubist & Winston Teague, i'll check my flange gasket. I'm not sure why i find the word flange funny
/quote]
Well Master Bates, it's all about mating surfaces. The flange around the opening, or port must be in good condition or leakage will occur. A leaking flange is rarely good news........