Performance mod - Polished Head???

[SuperDave]

I've been toying with this idea of polishing the combustion chamber to a mirror finish to enhance performance. My reason for thinking is thus: a semi-smooth or textured surface allows carbon to deposit, becoming a heat sink & lends to pre-detonation - knock & ping. If it were mirror smooth, it would
A) Reflect the heat back into the cylinder, aiding the expansion of the gasses and push down on the piston a little bit harder,
B) Discourage carbon buildup which might lead to pre-detonation,
C) Run cooler - the heat isn't absorbed as much into the head but goes out the exhaust.

I've looked around on the forums but haven't found much on this subject. I'm wondering if anyone has tried this, or if anyone has justification as to why I SHOULDN'T do this. Polishing the piston face might also be help too. I figured I could do this when I remove the head & jug to lap (sandpaper taped to glass) the mating surfaces for better seal (already blown 1 head gasket already) & maybe a wee bit of a compression increase.

 

[Deleted member 12676]

Still the carbon will build up on it, maybe at just a slower rate though. Go ahead and do it but be prepared to have to repolish it often if you feel it helps and you want the continued benefit.
These low rpm engines don't have a problem with detonation though.
I always thought that carbon buildup acted as a slight insulation. ... I just looked it up and carbon has only .8% the thermal conductivity that aluminum has. So my advice would be to leave the piston top and head surface "dirty" unless the buildup is causing too much of a compression increase.

 

[Fabian]

Polishing the combustion chamber to a mirror finish to enhance performance is like trying to polish a piece of bread and hoping it won't turn black when you throw it on a raging fire, as well as being more edible than a nicely toasted slice that's made golden brown.

The moment you run fuel through the engine and send combusted waste product out the exhaust port, the mirror finish you so carefully made mirror shiny by spending countless hours of your life polishing it to perfection will instantly become black with nothing more than an oily filth made out of pure carbon.

I'm fairly confident it will have "zero effect" on performance enhancement.

 

[Purple Haze]

On my first engine, I polished the combustion chamber, piston top, and all ports. After riding about 100 miles, pulled head and guess what? Carbon buildup on both chamber and piston top. My advice? Don't bother. Also, I didn't feel any increase in performance or see any gains in fuel economy. Spend your time on mods that will make a difference.

 

[Florida_Trail_Rider]

So you guys are saying port & polishing the intake & exhaust combustion chamber will do nothing in performance?

 

[Fabian]

So you guys are saying port & polishing the intake & exhaust combustion chamber will do nothing in performance?

It will do absolutely nothing for performance - it's a complete waste of time.

 

[Florida_Trail_Rider]

It wont hurt anyt5hing will it?I gutted my ports some and sanded them down smooth thinking I could force more air in and out..I also raised the pin on the needle was that a bad idea?I run 90 with no ethanol and 1 container of lucus smokeless oil to a gallon..New to these engines is that a good fuel source

 

[Fabian]

What i can say is that you "did not" do any research on this issue, despite the massive amounts of information on the internet and this website.

I spent a full 3 weeks researching everything about motorized bicycles and the available technology options; then hitting the credit card and purchasing components for my build.

 

[Florida_Trail_Rider]

No I did not Fabian,I just started researching last night my PC was down..Iv ordered another combustion chamber I take it ill have problems in the long run..

 

[Fabian]

If you do the research and choose the right components and make the necessary modifications, the engine will be surprisingly reliable.
Typically i get 4,000 kilometers (2,500 miles) out of a cylinder and my previous bottom end lasted 10,000 kilometers (6,000 miles) with a Jaguar CDI, which is seriously good mileage for $30 and $60 replacement items respectively.