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Polishing cumbustion chambers?

3K views 19 replies 9 participants last post by  roberto 
#1 ·
I herd that if u polish the cumbustion chamber of an engine it will give better effeincsy. That the shiny metal would reflct head back, and there will be less turbulance in the ingition of the explosion. Can someone give me feed-back on this.
 
#2 ·
Polishing the combustion chambers works in an all-out race engine, IF the chambers have been cc'd exactly. Polish won't give you any noticable results in a street and/or street strip application. Besides that it is tedious, time-consuming and dirty to do it right. Spend your time getting all the clearances exact and working on the tune-up, you will have better results.
 
#3 ·
I have to disagree. Better air flow increases power. With applicable bolt ons you will notice a difference. If you clean up the intake side and polish the exhaust side you will see a noticable difference. But remember make sure the intake ports and the cylinder head ports match. Also do not clean the intake up to much for a street motor you need turbulance or it will be a turd out of the hole.
But forewaring it is a dirty job.
 
#4 ·
Polishing is a waste of time, a rough finish outflows a polished surface due to reduced surface tension and a thinner boundary layer. How long do you think that shiny chamber will stay shiny? About 10 minutes I would guess.
 
#5 ·
No, the polished chamber won't stay shiney but what it will do is smooth out any rough or peaked areas in chamber. This will ensure EVEN combustion temperatures resulting in less chance for pre-ignition. If you're running stock compression ratios then don't worry about it but if your doing the run of the mill, flat top piston upgrade, which ups the compression a bit, then pay attention to the deck height (good quench is the goal here) and smooth out any rough surfaces on the piston tops and cylinders. The results will be that maybe you can still run regular gas and save a buck or two. The best thing is that we are not talking much money or time here and it WILL make a difference. Cheap SOBs like me pay attention to things like this!
 
#6 ·
I have ported and polished lots of heads, this also includes match porting the inlet and exhaust headers. the heads should always be "cleaned up" by remouving rough casting especialy around the spark plug hole. The results if done properly can be magic, but remember you may need to upgrade your carby jets and reset the ignition. You need to beg borrow or steel ENGINE BLUPRINTING BY RICK VOEGELIN. great read. Have fun
 
#7 ·
I will certainly agree with the recent posts, that MATCHING the intake and exhaust ports along with minor CLEANING UP of the runners, valve bowls and comuustion chambers will help the engine be more efficient. But actually POLISHING the combustion chambers is a futile effort unless you are building an all out race engine. As Jaw said, polishing can actually be detrimental to the intake runners. Clean up any rough casting areas, make sure your deck height is right, have a good quality valve job done, assemble it with care and go out there and kick some b__t! Just my opinion.
 
#8 ·
I've read that the exhaust is polished and the intake is left somewhat rough. Rough intake adds to fuel mixing and distribution in the camber. Smooth exhaust aids in ease of exhaust flow out. I'm not sure polishing the camber at the head would be that beneficial. Porting is definitely a good idea for better flow.
 
#10 ·
I'm going to be running around 9.3 to one compression ratio, so from the advice I have been getting I think it would be a good idea to polish the chambers to insure being able to use regular 87 octane gas. I also herd that polishing the chambers will reflect heat back. Which in term would give better effeincy and the motor would run cooler. Does anyone know how to go about and actualy polish the chambers. I was thinking of using emery cloth but I must insure even sanding. Anyone got any advice on how to do it??
 
#11 ·
Best way to polish cast iron or aluminum is to use a good electric or air powered die grinder that turns 20,000 rpm or more. Begin with an assortment of stones to get the roughness smoothed out (be sure to use stones that are rated for use with a high speed grinder. a cheap stone that comes apart at 20k rpm can be pretty destructive). Then, after the stones, use emory cloth rolls to polish. To get a real polish you can then go over the chambers with polishing wheel, using jeweler's rouge. This will almost make the area look like a mirror. Be careful that you don't take out much material from the chambers and watch out for the valve seats! Put a valve in the head to keep the stone from accidently hitting the seat (real easy to do, I can tell you from experience!). As you can see this is very time consuming and the materials to do it right are somewhat expensive. There is a place in California that sells all the supplies you will need: Cylinder Head Abrasives (www.ruffstuff.com.) Oh, be sure to wear good eye protection and some sort of a respirator. The dust you will create is very hard on eyes and lungs. Good luck and have fun.
 
#12 ·
Little known, less cared about fact; Did you know that a ginding wheel that blows up always breaks into three pieces? I read an car feature in a magazine many years ago ('42 Willys pickup, of course!) and the car owner took a year off during construction to recover from a grinding disk that disintegrated and imbedded in his chest.
 
#13 ·
How many horsepower does the magazine say you will gain by spending 40 hours polishing the chambers to a mirror finish? I'm curious. At 9.3:1 compression I doubt you will notice anything other than the reduced compression you will get from grinding material out of the chamber.

Maybe nickel plating would be a better plan, perhaps chrome? Now I'm starting to sound sarcastic, can you tell! If your looking for polishing compounds <a href="http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=jewelers+supply" target="_blank">here are some suppliers.</a>.

I would suggest you start with a satin finish compound and work your way to tripoli, rouge is a final cut and is very fine. See you in a year. Hey I heard drilling holes in the center of the beams of your conrods will lighten them and make your engine rev quicker, worth a try?
 
#14 ·
4Jaw is making good points and is being very kind. The top fuel dragsters MAY get a horsepower or two from this procedure(like they need it!) but they are running alcohol and take the heads off every run so they can keep them shiny. Trust me, a gasoline engine on the street will stay polished one or maybe two power strokes of the piston B4 it starts to carbon up. My hemi has factory polished chambers and every time I take the heads off I need to scrape off a carbon buildup. The radiant heat reflection benefit is milliwatts. The combustion benefits are negative in my thinking because turbulence is what we are all trying to achieve for good combustion. The only combustion chamber work that makes any sense to me at all for the street/strip engine is to knock off any sharp corners that may provide a hot spot for pre-ignition. Everything else is a waste of time.

[ August 30, 2002: Message edited by: willys36@aol.com ]</p>
 
#15 ·
Hey, if the gent wants to polish his chambers then let him. I know that I look for any excuse to go into the garage to get away from my five screamers and the misses who always has her "hands on her hips". If David Vizard (Chevy God) says that it's benificial, then thats good enough for me. I polished up my chambers and noticed that I don't "need" a drink any more, plus my mariage is doing better!!
 
#16 ·
Hey, I polished and clear powder coated the PowerGlide in my son's Pontiac and you can't even see it from the top! I am not opposed to doing stuff that only makes me feel good, that no one else sees. Just realize, it won't make any performance difference.

[ August 30, 2002: Message edited by: willys36@aol.com ]</p>
 
#17 ·
Im not really looking for horse power out of polishing them im just looking for effeincy. Im 16 now on a low budget with a lot of time to do stuff like this. The heads are for a sbc 350 that is going in my 69 firebird. I hope to get over 20 mpg. So im just hoping that with my 9.3 to one compression I would still be able to use regualr gas to save me a few sence. Also the new cam that i put in has almost no over-lap. So im a little afraid of pre-ignitoin, does anyone think that polishing would be able insure no-pre-ignition??
 
#18 ·
NO! if your polishing reflects so much heat back into the chamber it will preignite sooner. You would be better off ceramic coating rather than polishing. Spend your time on parts of the heads that will gain from your hard work, port matching, short side radius blending, bowl blending etc. etc. etc.

There are many other areas where you can actually gain, this is not one of them. How you spend your time is up to you.
 
#19 ·
No it won't insure against pre-ignition. The part of it that will reduce the chance of pre-ignition is to round off any sharp edges. I'm not talking about taking off 1/8", just gently smoothing anything that looks sharp. 9.3 is not a radical ratio so if you set up your timing and carb anywhere near optimum, you should be fine, even on 89 octane.

If you want to do some head work that improves efficiency, study porting your intake and exhaust passages, matching manifold and head ports, releiving the port area under the valves, and doing a multi-angle valve job. These are things that will give you measurably better efficiency and performance.
 
#20 ·
If you want to polish the chambers I think it will help. CC them before going to work and make them equal too. This way you can maximise the ignition timing. Think also about the shape of them. The hi velocity air movements from the intake accross the valve seat needs to follow the metal wall as it enrters the chamber or velosity is lost. The exhaust should be considered too. Make the exit smooth by radiasing near the seat to guide the air out accross the valve seat. This is not to be done without an in depth study of why you are grinding where but it is done all the time. Follow the shapes you see on some of the aftermarket heads.
 
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