Doesn't make sense 

The timing on the right side is set to the marks all good the ,left side set to cam pulley mark engine runs hot and under load and pings set  mark on left side cam pulley after mark engine pings when not hot under load and  looses power , set to cam pulley before mark engine runs ok doesn't ping or get hot .

 Mark refers to the slot on the back timing belt cover . Any ides why  cam pulley has pin so can't be wrongly positioned , timing is set by no1 plug on opposite side (piston 1 ) 

There are threads on here about how to install timing belts. I'm on mobile, can't link them. The flywheel mark is the center mark of the 3 lines, not the TDC + angle marks. The edge of the arrow in the view port is to align with the center mark. Passenger side belt goes on, hole on pulley aligned with notch on top of plastic. Any belt slack on the tensionerror side. Then turn the crankshaft 1 full turn. Put on drivers side belt, pulley hole aligned with the top notch. Any slack on tensioner side. Re check after setting the tensioners. The timing holes on the cam pulleys must be 180 degrees apart.

These alignments I know and have followed. Left side (facing foward) when the hole in the in the pulley aligns with the notch in the plastic it slowly overheats when driven constantly at 110 kph - (65mph ) or higher and pings under load when temp exceeds normal   .When the hole is after the notch say one belt notch towards  1 'clock it consistently pings when under load but doesn't get hot yet when one belt notch before the plastic notch say towards 11;oclock it runs fine.      Doesn't make sense andI

Maybe the distributor is off position, or off a tooth.

This is an Awesome Video by MilesFox:

 

Sounds like the ignition timing is advanced.

Thanks for help. Problem was distributer vacuums advance bellows stuffed would not advance the timing.

Grandson said sounds like timing isn't advancing under load smart little bugga only 11.. A suck on the tube and tongue over tube hole no hold vacuum . God help us oldies ,New dizzy , reset back to mark runs fine 

 GUESS WHO FEELS STUPID 

You might also want to check and see if the radiator is plugged up or restricted. This can also cause the temperature to creap up at speed. Good on your Grandson, sounds like a tech in the making 

Edited February 27, 201511 yr by Crazyeights

but...overheating can be from too much advance. not from too little advance.....

 

the vacuum advance really drops out under load, when you have foot on it, lesser vacuum - leaving it up to mechanical advance centrifugal weights.

Your old dizzy advance springs gone crappo maybe?

 

Try blocking off the vac line with new dizzy installed and see if symptoms return p'raps?

I have found the difference between vac advance working and not working is more just a crisper sweeter light throttle respnse when it is working

 

Good that you got it sorted easy though