Hgpilot

Yeah that's what I thought, but no they are all touching. Some are just pushing the spring down more than others. Yeah dad is a Bush mechanic alright, he will probably look for a straight enough stick to put in there! 

Thanks, I pulled the rocker cover off (didn't unclip the throttle cable though :/) and sure enough I have a loose intake push rod and the exhaust rod is not even connected! 
 
Check this out! (ignore my noisy kids)
 
 

Ok, So, you guys must be right. Pulled all leads off one at a time and sure enough... stops popping when cylinder 4 lead is off. In fact, it runs smooth as with cylinder 4 unplugged. I can't touch the exhaust on all cylinders except 4 I can grab hold of. I have never worked on a push rod engine before, and I am no mechanic but I will see what I can do. Any suggestions on what I do from here? Thanks! 

Yeah new plugs and new leads Bear 
 

Alright, update! Dad came over and we pulled the 2 lifters and rods out. Both rods were straight so we put them back in and fired it up. It runs! No pop! Revs up and idles no problem!.
The exhaust lifter is working like a new one. The intake lifter on cyl 4 on the other hand is still a bit loose and tapy. Dad thought that with an engine flush and some new oil the rod might pump back up. Put new oil in and had engine flush along with some liquimoli lifter juice stuff but still lifter taps. I think I should have just put a second hand lifter in like you said deankdx. 
Anyway thanks for your help guys! It's going pretty well now because of the advice I have got here. I will no doubt be back with more questions soon. Thanks! 
 

Yeah that's what I thought, but no they are all touching. Some are just pushing the spring down more than others. Yeah dad is a Bush mechanic alright, he will probably look for a straight enough stick to put in there! 

Thanks, I pulled the rocker cover off (didn't unclip the throttle cable though :/) and sure enough I have a loose intake push rod and the exhaust rod is not even connected! 
 
Check this out! (ignore my noisy kids)
 
 

Here is a video of it running when cold
 
https://youtu.be/qquUU1uhZEU 
 
And when its warm
 
https://youtu.be/S0t5a5eNbfE
 
Let me know if links dont work. Thanks!

Yeah it no doubt is perished on this old thing. I will check it out tomorrow arvo!