Pinto Ping

Hi All,
 
I have just picked up a mk1 with a pinto conversion and it seems to have a relatively consistent slight ping to it that is there when its cold or warm.
 
At idle its there a little bit, when i accelerate it might come and go, when im cruising around 3000 RPM at a constant speed though (like on a main road holding a constant speed) it disappears and then might come back ever so slightly.
 
Things i know about the car that i think may be contributing:
- there is a vacuum leak i suspect somewhere because when i stick my foot on the brake at the lights the rev's raise
- it has a brand new 32/36 carbie on it and im not sure what any of the jetting is
- i have checked the timing and all timing marks are lined up correctly (cam, dizzy, crank) and at idol (with the vacuum advance still connected) its sitting around 8' TDC.
- the temp seems to continue to slowly climb up over a period of about 30 mins where it gets to the point that it is almost at the red and i shut it down.
 
Suppose my questions are:
1) Does it sound like its being caused by running lean, potentially from the vacuum leak, potentially because of the unknown jetting.
2) Would the right approach be to block the booster vacuum connection on the manifold (booster / dodgy line is where i suspect the leak is), fire it up, confirm the timing is correct again and test to see if the ping is there (can replicate the ping by just holding revs slightly off idol)
3) What are the chances its an issue potentially with the vacuum advance on the distributor, is it worth blocking that too and setting the timing again and testing? Is that the best way to set the timing.
 
Any experience that can be shared with this kind of issue would be greatly apprecaited.
 
Thanks,
 
Josh
 
 
 
 
 
 
 
 

Thanks Mark,
Hopefully this weekend i can get a couple of hours to have a look. For the sake of $20 i might just replace it anyway so its one less thing to worry about. Thanks again!
Josh

Whooligan has probably nailed it. 
I have been continually warned by people employed in the petroleum industry that the quality of petrol is now very poor. Apparently Australia is a dumping ground for poor quality imported fuel.
This time last year I had fuel related problems from using 91 octane fuel in a car I have owned since 2001.
I now only use good quality 98 octane.
Very questionable however impossible to prove if 91 octane is actually 91, and 98 octane is actually 98.
Unfortunately we live in a commercial world where the profits of powerful multinational companies take precedence.
 
 

Josh, is your compression ratio too high fir the fuel and perhaps try colder plugs. I had similar issue and part of it was that the machining done on the head created sharp edges which developed heat concentrations. Something to consider
Rodney

Engine ping is usually constant, usually happens during acceleration and is telling you that the ignition timing for the compression ratio and fuel octane and engine speed is incorrect. Is easy to determine on a dyno and usually can be eliminated, but not always as the fuel octane rating may not be available or financially viable even for a track car.
It is the onset of pre-ignition or over advanced ignition in most cases and is not to be confused with actual mechanical noise from any source which have to be eliminated first.
 
 

Hi Deano,
I have a 1600 van. Daily driver until two years ago. Mechanicals all standard.
I use only 98, no additives.
Timing is as factory specs.
If the fuel is more than 1 year old best to drain it completely.
Learn to tune it yourself.  5 minute job.
:)