<VV> strange engine sound (pinging?)

[Tony Underwood]

At 02:36 AM 6/2/2010, Ray R. \(aka Grymm\) wrote:
>Hey guys, since you were talking about pinging I had a question for you...
>
>Under load at medium throttle I get a rather quiet and subtle 
>whistle/jingle bells noise...   It doesn't sound very much like 
>pinging (which I'm very familiar with) but it's just close enough 
>that it worried me for a bit...   the key thing here is that if I 
>step down and give it considerably MORE throttle it goes away 
>despite still being under a heavy load... from my experience pinging 
>would get worse if I did that... but on the other hand maybe it 
>richens it up enough to make the pinging stop?
>
>I've had Corvairs ping before.. I tried for a while to get a 110 
>auto to run on regular (unsuccessfully!) and heard plenty of pinging 
>then.. this is different and subtler but I'm paranoid it could be a 
>VERY light ping I guess.  In case you were wondering I did get the 
>timing retarded far enough to run on regular without pinging.. but 
>with the timing that far off my mileage went from about 20mpg to 
>about 12... LOL!
>
>The sound could also be belt or intake related... but it only does 
>it under load when driving so its hard to track down.  It's a pretty 
>low sound.... like hearing a salvation army guy from accross a 
>parking lot at christmas time...  and it's so close to a whistle 
>that I'm not sure it isn't one.  I might try to get a recording but 
>it will be pretty tough to hear it over the rest of the noise.




Check your vacuum dashpots close, see if one of them has a split diaphragm.

Pinging under light load that stops when you give it more throttle is 
usually gas that's not up to the task, ALL ELSE being equal.   The 
dashpots will kick the ignition advance right up there under light 
throttle and on a 110 with anything less than premium fuel will ping 
in dry summertime weather under light loads.

...and a split diaphragm in one of them will whistle under part-throttle.



tony..