Performance mod - Polished Head???

SuperDave

SuperDave

Member
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.

usflg
 
I was considering doing the same thing, minus the piston polish, though I don't see why THAT wouldn't hurt.

All I need to know is how to go about it. :D
 
Polish isn't easy, well, maybe it is, but it's time consuming & labor intensive. I hand polished the covers of my motor and that took me about 20 some hours. But essentially, you start with 80 grit sandpaper and hand rub the dome of the head until it's all uniform. Then you switch to a finer grit, say 100 or 120. then do it again with 200, 300, 440, 600, then 800 grit. Your hands will get sore and by this point you might be willing to pack it in. I'm OCD so that rarely happens but your mileage may vary. If you can FIND it (try auto paint suppliers or auto body shops if there's any near you) move on to 1000 grit. I couldn't find any so I used Turtle Wax Rubbing compound & a buffing kit I found at the hardware store, it goes on the end of a drill. Once that's as shiny as you can get it, then move on to Mothers Mag Polish. Go over it 2 or 3 times and you'll see a mirror like finish to rival chrome.

Now this is how I polished my motor covers, I haven't popped the head to my motor yet to tackle the combustion chamber. But the method is essentially the same. I also used a Dremmel and used up 2 packages of little buffer wheels, I had to in order to get into the tight corners on the clutch cover that the 4" buffer/drill couldn't do. Depending on how deep the dish on the head, I might have to go buy more.

If this helps you, kudos. It ain't easy, but it is worth it for the looks.
65725_10151432156864894_657188609_n.jpg
 
polished head, piston crown and the exhaust port is a good idea. a satin finish on the intake and the transfers will discourage droplet's from forming. a long pipe made from electrical conduit wont make it faster but will get rid of the weed wacker sound and i think looks better.
 
Going way back to the old drag race days, there were two schools of thought on polishing the combustion chamber. One said, as Dave did, that it enhanced the flow and kept carbon build up to a minimum. The other side said that a rougher surface broke up the fuel/air charge into smaller droplets and therefore made combustion more efficient.

I don't believe there was ever a provable consensus on either theory.

Try it, Dave, and let us know but take the time to do a comprehensive comparison.
Do several speed runs both before and after using the same route each time.

Tom
 
This is really an interesting theory that I have never considered. The perfect explosion also will need a combustion chamber with surfaces that have a mirror-like finish, called surface finish and measured in microns. I used to do moldwork in the plastic injection industry, so I do think you are on to something with the metallurgy with this:

Check out this article:
http://www.balesmold.com/diamondpolishing.htm
 
Looks like I'll have some parts-running to do.

*threadjack*

I don't want a mirror finish, but I want to take off the mini-mountains on the head, what grit paper do I use? I just want to smooth it.
 
2door said:
Going way back to the old drag race days, there were two schools of thought on polishing the combustion chamber. One said, as Dave did, that it enhanced the flow and kept carbon build up to a minimum. The other side said that a rougher surface broke up the fuel/air charge into smaller droplets and therefore made combustion more efficient.

I don't believe there was ever a provable consensus on either theory.
Tom
Click to expand...

Indeed, a rough surface promotes "tumbling" of the mixture, broadening the torque curve, especially in the low-end.

A smooth surface promoting flow will increase peak horsepower, as we all know an engine is essentially an air pump.

In the end, I spose it's up to the person with the engine which they feel is more important. IMHO, for a daily rider, port-matching is a good thing but fully polished is not. When you go fully polished, you will notice that you've gained some horsepower and top speed capability, but you have lost some low-end grunt.

Many automakers have been designing the "tumble" effect in their intakes for years. The GM LSx and new LTx are perfect examples.
 
The_Aleman said:
Indeed, a rough surface promotes "tumbling" of the mixture, broadening the torque curve, especially in the low-end.

A smooth surface promoting flow will increase peak horsepower, as we all know an engine is essentially an air pump.

In the end, I spose it's up to the person with the engine which they feel is more important. IMHO, for a daily rider, port-matching is a good thing but fully polished is not. When you go fully polished, you will notice that you've gained some horsepower and top speed capability, but you have lost some low-end grunt.

Many automakers have been designing the "tumble" effect in their intakes for years. The GM LSx and new LTx are perfect examples.
Click to expand...
So, polish (smooth) the exhaust port, shave the head, but leave the texture in the combustion chamber? I don't know about yours, but mine gets really dirty and I know that can't be good for it as I have cleaned the head then ridden it and there was a marked performance increase.
 
dodge dude94 said:
I don't want a mirror finish, but I want to take off the mini-mountains on the head, what grit paper do I use? I just want to smooth it.
Click to expand...

For a satin finish, I'd start with course grit and then quit at around 600 grit. Use wet or dry sandpaper, but sand it wet, it prevents the paper from loading up fast.

If you've cleaned the gunk from your head & saw an improvement, then yes, this sounds like a good mod for a performance boost.

usflg
 
In my experience, polishing the head won't make enough difference in power to be noticable, but it will stay carbon-free longer. Go for it, but don't expect huge gains...
 
SuperDave said:
For a satin finish, I'd start with course grit and then quit at around 600 grit. Use wet or dry sandpaper, but sand it wet, it prevents the paper from loading up fast.

If you've cleaned the gunk from your head & saw an improvement, then yes, this sounds like a good mod for a performance boost.

usflg
Click to expand...

Alright, cool.

Anybody know anything about that darn ridge extending out from the head mating surface?
 
dodge dude94 said:
Alright, cool.

Anybody know anything about that darn ridge extending out from the head mating surface?
Click to expand...
That is the gasket mating surface. It needs to be absolutely flush with the cylinder to assure a good seal against the head gasket. Some grind it off but if you do that you need to make sure you make it flat again with no high or low places and no angles. The increase in compression is negligible so there's no real advantage to removing it.

Tom
 
2door said:
That is the gasket mating surface. It needs to be absolutely flush with the cylinder to assure a good seal against the head gasket. Some grind it off but if you do that you need to make sure you make it flat again with no high or low places and no angles. The increase in compression is negligible so there's no real advantage to removing it.

Tom
Click to expand...
I'm talking about this ridge, right here:

2wrq73o.jpg


See arrow. :)
 
Yes, and that's what I'm talking about too.
Yours looks a little rough. Lay the head on some 220 grit sandpaper that is laying on a sheet of glass or any known flat surface and move the head in a circular motion. After a few rotations look at the head and you'll see if it is smooth or not and you'll see any high or low spots that need to be removed so the gasket will seal against it properly.

Tom
 
It's not actually rough, I don't think, but I do know that there was some stuff on it.

I have nothing to do today, so I guess I'll go over to wally world and pick me up some sandpaper. :)
 
dodge dude94 said:
It's not actually rough, I don't think, but I do know that there was some stuff on it.

I have nothing to do today, so I guess I'll go over to wally world and pick me up some sandpaper. :)
Click to expand...
I should have added that after you see where the bad areas are and have smoothed them down, work up on the grit of your sandpaper. I usually don't go any further than 400 grit but some will say even a finer grit, down to 600 is needed. I've never had a problem.

While running the head over the paper you'll want to make sure you don't sand an angle into the gasket surface. Keep rotating the head in your hand and use the old "wax on, wax off" motion. Circular, as if you're applying wax to a car but also changing the position of the head in your hand. I hope that's clear. Most important is the surface you use under the paper. Glass is the very best but even a Formica counter top will work. Marble is good too as long as it is smooth with no ridges or bumps. It must be flat; as flat as glass to assure you don't sand gouges into the surface.

Good luck. Show us the results.

Tom
 
2door said:
I should have added that after you see where the bad areas are and have smoothed them down, work up on the grit of your sandpaper. I usually don't go any further than 400 grit but some will say even a finer grit, down to 600 is needed. I've never had a problem.

While running the head over the paper you'll want to make sure you don't sand an angle into the gasket surface. Keep rotating the head in your hand and use the old "wax on, wax off" motion. Circular, as if you're applying wax to a car but also changing the position of the head in your hand. I hope that's clear. Most important is the surface you use under the paper. Glass is the very best but even a Formica counter top will work. Marble is good too as long as it is smooth with no ridges or bumps. It must be flat; as flat as glass to assure you don't sand gouges into the surface.

Good luck. Show us the results.

Tom
Click to expand...
Alright, thanks for the advice. Strangely enough, I've got a large sheet of glass sitting around from our old storm door. :D


I will end up doing it next week more than likely as it's cold right now and I really don't feel like getting out. lol
 
dodge dude you cylinder head looks pretty rough there, to be honest i don't think theres much need to polish it but a bit or work with some finer sandpaper might help a bit. Also if you looking for performance increase there are plenty of mods out there that don't take much time and can yield beneficial results. If your looking to modify the head for more power try making a better squish band.
 
Sand your combustion chamber down a bit by hand, to get most of the paint and/or roughness off, then take a dremel tool and use a BRASS wire brush, that will bring out a real nice smoothness.
 
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