360 engine... sounds like diesel engine on light acceleration

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Claude C

Claude C

Twin '66 Cudas
Joined
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Have a 1966 Barracuda that had a 360 in it (mfg 1984). Car just got put on the road (bought as a parts car but decided fix up and put on the road). On mild acceleration it sounds like a diesel engine, sort of pinging?? On hard acceleration or holding at steady speed the noise is not heard. Not sure what the issue might be. Otherwise runs great with plenty of power so don't think it's timing. Any ideas?
thanks-
Claude
 
figured I'd add a photo :)
1966 barracuda Red.jpg
 
Maybe it's the chunks of wood dragging under the car?

:rofl:

Couldn't help myself:rolleyes:


We are assuming it has a standard distributer type ignition system.

It sounds like you are describing pinging, an easy way to check is to set the initial advance to 0 and remove the vacuum advance hose and plug the hose.

If the pinging goes away you have a starting place.

In a side note..

If the vacuum advance was supposed to be tied to a particular port on the carb, but is on the wrong port, you might get too much vacuum at the wrong time.

For instance if it was on manifold vacuum...

(NUMBERS BELOW ARE FOR EXAMPLE ONLY NOT INTENDED TO REPRESENT REAL WORLD NUMBERS, JUST THE WAY THE TWO ADVANCE MECHANISMS INTERACT WITH EACH OTHER )

At idle it would be seeing full vacuum (15 inches) but with low rpm no mechanical advance, so timing would be initial plus full vacuum (10+15 deg = 25 deg) At full throttle the vacume would be lower 5 inches, But rpm would be high so mechanical would be all in and the engine would have maybe initial 10 plus mechanical 25 to 30 deg so 35 to 40 deg advance

At part throttle, vacume would be higher (10 inches) rpm would be higher so some mechanical advance would be in. So perhaps you have initial + vacuum + mechanical 10+ 10 + 20 so 40deg or more.

AGAIN NUMBERS FOR EXAMPLE ONLY
 
Dana67Dart said:
Maybe it's the chunks of wood dragging under the car?

:rofl:

Couldn't help myself:rolleyes:


We are assuming it has a standard distributer type ignition system.

It sounds like you are describing pinging, an easy way to check is to set the initial advance to 0 and remove the vacuum advance hose and plug the hose.

If the pinging goes away you have a starting place.

In a side note..

If the vacuum advance was supposed to be tied to a particular port on the carb, but is on the wrong port, you might get too much vacuum at the wrong time.

For instance if it was on manifold vacuum...

(NUMBERS BELOW ARE FOR EXAMPLE ONLY NOT INTENDED TO REPRESENT REAL WORLD NUMBERS, JUST THE WAY THE TWO ADVANCE MECHANISMS INTERACT WITH EACH OTHER )

At idle it would be seeing full vacuum (15 inches) but with low rpm no mechanical advance, so timing would be initial plus full vacuum (10+15 deg = 25 deg) At full throttle the vacume would be lower 5 inches, But rpm would be high so mechanical would be all in and the engine would have maybe initial 10 plus mechanical 25 to 30 deg so 35 to 40 deg advance

At part throttle, vacume would be higher (10 inches) rpm would be higher so some mechanical advance would be in. So perhaps you have initial + vacuum + mechanical 10+ 10 + 20 so 40deg or more.

AGAIN NUMBERS FOR EXAMPLE ONLY
Click to expand...
Well said 67Dart !! Covered all bases and well written :thumbsup: thank you.
 
Post a video of the engine running with audio.
 
Claude C said:
Have a 1966 Barracuda that had a 360 in it (mfg 1984). Car just got put on the road (bought as a parts car but decided fix up and put on the road). On mild acceleration it sounds like a diesel engine, sort of pinging?? On hard acceleration or holding at steady speed the noise is not heard. Not sure what the issue might be. Otherwise runs great with plenty of power so don't think it's timing. Any ideas?
thanks-
Claude
Click to expand...
What'syour timing specs? Initial timing with vacuum advance disconnected and plugged? Total advance at rpm?

Disconnect the vacuum advance hose at the distributor and plug it with a golf tee or screw and test drive. Did the ping go away ? Has your distributor been messed with internally?
 
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