AC170 gas carb blowup!!

Grinding shelled corn for cow feed(NH353) when the engine misfired, caught again, ran Ok for a few seconds, then misfired again!  Had a strange loud puffing sound instead of normal running.  (Grinder inertia, keeps engine turning long time).  Ran OK for minutes, then misfired again, this time for longer!  Had to shut off grain flow into grinder as this time slowed down to quite slow PTO speed and again with that strange puffing sound, and then stopped.  Examined the tractor and saw that the carburetor inlet hose had blown up REAL BIG like a balloon! and the dust cup on the dry filter in front of the radiator had popped off!!! Towed the tractor away and put WD on the grinder to finish grinding.  Tractor started later when cool, drove over to Jack the friendly neighbor mechanic, who said "Bad exhaust gasket, I heard it coming down the road!!" Carburetor was dripping gas also, so ordered manifold gaskets and Permetex RED for the manifold.  Manifold did not need machine shop work to seal up to the block.  But Jack had a difficult time getting the carb to stop leaking, eventually saw that the float was damaged(see picture, top of left float). So after 2 months, I thought it was fixed! Big surprise, put it on the grinder again, and soon it began missing just as before, stopped before more damage was done, put WD on again.  More guessing and troubleshooting, eventually got smart, put a voltmeter on the junction of the ignition resistor and the coil, should be 6 volts(engine stopped, key on).  Wiggled wires and terminals, made the voltage there jump up and down to 3 volts!  So the resistor is bad, see below.  Ordered a new 1 1/2 ohm resistor labeled as such on webpage(but not on the resistor), measured it before install, it is 3 ohms!!!  Called seller B*******, got him to check his stock, he said "I will refund, do not send back". He did refund, but I sent back anyway! So I went looking for a better quality resistor, found this OHMITE from Mouser:

https://www.mouser.com/ProductDetail/Ohmite/F40J1R5E?qs=00dioisqAT%2F9BXfa7b7AWQ%3D%3D

Ordered the 40 watt size(larger than needed) but I wanted to have it run cool!  Installed, soldered the wires to the resistor(no loose and wiggly Faston terminals) See picture. 

Has run about 6 weeks now, 5 loads of feed grinding, works perfectly!!!

Those resistors can be found on Ebay, at auto parts stores, etc. but are very poor quality and not usually labeled with an ohms value.  The wire winding inside is not sealed, is made of iron and will corrode with condensation and over time. The terminals are crimped on and will loosen as they will wiggle with vibration.  See picture, the ceramic mandrel inside the resistor on which the iron wire is wound is cracked!

This whole episode took about 6 months to unwind,  but glad to get running again!! I am assuming that this carburetor explosion was caused by leakage from manifold gaskets.  Has anyone else seen similar???

I remember starting Dad's WD45 in the dark when I was a teenager. We were amazed how many sparks were jumping around. 

A new set of plug wires made a huge difference.