Why is my Torry pinging?

As above suggests, The car in question is LJ XU-1 it runs on BP Ultimate 98 I took it for a long run 160 ks and coming up the Toowoomba range in top gear and gave it some gas and you could here it ping so I dropped it back to third to stop it apart from that it seems to be running fine.

So what have I done or haven't done?

Carbies out of tune? I haven't tuned them for quite a while.

Stale fuel or inferior fuel? I put $70 in it and also put some fuel conditioner in.

I haven't checked the timing yet, it has a Petronix electronic ignition installed 6 years ago.

Thanks in advance. John.

Could be a few things or combination of things... Going up hills in top gear puts the engine under alot of load so is when it will ping if ever.

Could be:

-Old fuel loses octane but you said you put $70 of new fuel in? so shouldn't be that

-Air/Fuel mix too lean under load, Im not familiar with the Toowoomba range? how high above sea level were you? The higher you go the richer your mixture will get.

-Ignition Timing too advanced

-Was the cooling system getting hot? a Hotter engine will put you closer to detonation.

-Too hot a spark plug can also cause it or other hot spots in the combustion chamber.

But is most likely too much ignition advance, Or too lean... Best bet would be to get it on a dyno for a tune. Fit new set of plugs and fresh fuel before going tho.

Does the Pertronix electronic ignition still use the original vacuum advance ?

Thanks for the replies. The carbies are most likely out of tune. The GMH instruction manual states to screw in the needle? untill it just touches the piston? and then screw out 2 1/4 turns is this still correct procedure? Toowoomba is approx 700m ASL.

Yes the dizzy still uses vacuum advance, I haven't checked the timing for ages either. Engine temp normally sits around 1/4 on the gauge but going up the range it climbed up to half.

Again thanks for the info gents.