Weird question

bobcat2

Tractorologist
Senior Member
Member
Hello all,

Let me preface this with the fact that I am not an engine expert...

As I'm rebuilding my HH120, I got to decarbing the piston, valves and head. I have time on my hands while I paint and tinker with other stuff, and wanted to run an idea past y'all. Would it hurt/help if I polished the combustion chamber? I know from lapping rifle barrels that I greatly reduced fouling and improve accuracy a bit, so I assume if I smooth out the rough spots in the combustion chamber, carbon deposits should have a harder time building up on the surface, correct?

I wasn't sure if going over the areas with a Dremel and felt pad using flitz metal polish first, then a round of JB bore paste would hurt anything? I know it's not needed, but it's been one of those projects that I've been going out of my comfort zone and experimenting new things with.

Thanks,
bobcat2
 
I've always been of the opinion that carbon buildup in the combustion chamber, and piston is a result of a worn oil ring letting enough oil leak past it to form the carbon. With a proper overhaul and care it should take many hours for the carbon buildup to start again. The polishing shouldn't do any harm.
Mike
 
Easy way to remove carbon; spray on Permatex Gasket Remover, let sit for 10 minutes and wipe carbon off. To keep carbon out of the combustion chamber, use Seafoam.
No, polishing the combustion chamber won't hurt anything. If you enjoy it, do the ports as well.
 
that was a big part of the Kirk's Killer Kohler....but skip the JB Weld.... it won't last in the combustion chamber very long, under those conditions...

When I worked at a different job about 15 years ago, a fellow coworker told me of his Dad's Ford Exploder, which had cracked its heads, well his Dad had taken the Exploder to the "most recommended" side job guy around at the time, when it came to engine repair.... this genius had done lots of work for the local Mom and Pop used car lots in the area.
One day Steve was telling me what this guy had wanted to do with those heads and I cringed... wanted to seal the cracks in the heads with JBWeld.... "its cheaper than another set of heads"...About 4 days later Steve was telling me that "it ran great the 1st day he had it back but by the 2nd day, it was back to smoking its white cloud and running as bad as it had, before this side job guy had even touched it".... Not a knock against people who do side work, not at all.... but wow/// JB Weld works on SOME things but as I told Steve then, that is one of the absolute last places I'd want to try it..... BEFORE his Dad had told the guy working on it to go ahead and fix it that way. after wasting all that money on labor, gaskets and all the other associated costs with pulling the heads, I think he wound up junking the Exploder. I remember being asked if I wanted to redo it, and I said "sorry I wont touch it"....
 
Normally with head work, you polish the head chamber and exhaust port. The intake runner gets ported, but you don't mirror polish it which helps with atomizing of gas molecules.
Go for it if you want to, won't hurt anything.
 
Let me preface this with the fact that I am not an engine expert...
Taking into consideration your statement I would like to offer this, do not use a wire wheel on the sides or top of the piston. It will remove aluminum almost as fast as carbon. The use of the products listed above or careful use of a putty knife on the head of the piston is acceptable.
 
Probably one or two at the most bottles of K-Seal would have taken care of it. Fixed several leaking heads getting that tell tail white foam in the oil dip stick. A Dodge van I had developed a cracked head. One bottle of K-Seal and drove it up the interstate at 70 mph for 2 hours heal it right up.
 
Hi @bobcat2 , was the HH120 smoking? Like was said by Mike up there, black carbon deposits are usually from oil consumption. Did the top of your piston show a clean spot where the aluminum is visible? That's oil washing up through the rings.
HH120 piston & valves 001.jpgHH120 piston & valves 002.jpgHH120 piston & valves 003.jpg

This is what the front of the top ring land looked like after pulling the piston in the area where that clean spot is.

HH120 piston & valves 019.jpg

The cylinder was egg-shaped bad enough that the piston was cocking in the bore enough to scrape the ring land like you see.
It needed a overbore of .020 to true up the cylinder. At that time in 2013, no overbore pistons and rings could be bought for any price, and I put up with the smoke for two more years after doing a standard bore overhaul. It was getting pretty tiring being the smoke cloud in the neighborhood so I checked on overbore pistons again in 2015. Nothing available. My wife and kids bought me a HF 13 HP engine for fathers day that year and the tractor got a re-power that fall.

I just thought I would let you know that overbore piston/rings may be impossible to find or afford for an HH120.

Good Luck!
DAC
 
@bobcat2 ,

If you'll run a little Sea-Foam in the gas the carbon buildup will go away. You can also clean the carbon out by trickling a little in the carb whiles it's running. Be prepared to give it throttle to keep it from dying and also you can expect a big white cloud out of the exhaust as it cleans and burns out the carbon.

The Sea-Foam will also help keep the fuel system clean and free of issues from Ethanol.
 
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