I'm working on the spare cylinder head for my motor and would like opinions about polishing the combustion chambers. They are as they came from the factory right now with the casting "fuzzies". Is is worth the effort to smooth it out? I don't mind doing it..it's a hobby :).. Of course I'd be wildly happy if I got some performance gain out of it although I doubt I'd ever notice it. I guess it's the old hot rodder reading from way back about ".060 over, ported and polished" what ever motor followed by a cool picture what lingers in my head. Seems like the thing to do. But is it worth the effort?

Thanks:
Paul...aka Xerxes

For the most part,it is just done for cosmetic reasons.
You just need to smooth out all the sharp edges that could cause local hot spots that can cause potential preignition.

Really ,you will not see any performance gain.

If the chamber is smoothed out, it can be able to clean up carbon deposites a bit easier than a rough chamber when injecting alcohol or water injection,,,,but even w/rough chamber the use of water or alcohol injection will keep the chambers clean.

MBHD

I don't know what 6 head you're condsidering porting and polishing,but inline 6's are notorious for not having good exhaust flow.I would consider doing the the job.

Thanks MBHD and Drew.

I think I'll just smooth out the sharp edges as you suggest Hank.

Drew..this is the f-head 161 Willys motor. The exhaust valves/ports are in the block like a flat head. The intake valves and ports are in the head. The six cylinder (mine) was an integral intake cast into the head. I've machined the side off of that to open it so I can install a simple plate/manifold for two side draft carbs. I've been smoothing out the lumps and bumps in the plenum area and rounding the shoulders off of the air passages into the combustion chambers. There were a couple of 90 degree corners and also "L" shaped steps in there.

Thanks for the replys:
Paul..aka Xerxes

LOL! I wasn't even close on that suggestion.So smoothing is definitely the way to go until you gain more info into modifying this type head. It would be nice if you could use someone's experience for blending the "L".

Drew:
Thanks :).. This is definitely a situation where I'm "breaking trail" so to speak. I've seem pictures of two instances where people have done what I'm doing as far as the manifold is concerned. One happened probably 45 years ago, the other I don't know, likely more recent but I can't find the person involved with that. So, I'm on my own, with the collective knowledge of this group. Every bit helps!

Thanks again:
Paul...aka Xerxes

I read an S.A.E. paper written by a Japanese auto maker who studied polishing the combustion chamber and piston tops in a production based engine. They also studied various commercially available reflective ceramic coatings that are available. There conclusions were that polishing all of the components that "see flame" in an engine led to increases in performance and fuel economy on the order of 1 - 2%. Interestingly, none of the high temp coatings showed any improvements in efficiency whatsoever. Their conclusion was that although polishing helped, it was not economically feasible in a production engine.

Or so they told the rest of the world.

I polish my chambers and piston tops in every racing six I build. Hey, in a 500 HP engine 2% is an extra 10 HP for a few hours of work and no money. I'll take it.

Would you have the SAE paper number handy?
It sounds interesting, I would like to read just what they found.
Thanks for the comment

Polishing the chamber also keeps carbon from building up and the polished surface reflects heat back into the cylinder. Our latest race motor has piston tops polished to look like chrome along with the chamber in the head. A lot of builders polish the exhaust port to a mirror finish to reflect heat and to keep the build up to a minimum. The intake runners should be as cast or rougher, you don't want them shinny at all. Fuel will stick to the smooth sides and fall out of atomization then set on the runner floor.

Joe

Sorry Deuce, I don't have it handy - I packed it away when I retired. I seem to remember it was published in the late eighties. S.A.E. probably has a website, but you may have to be a member to get in.

The study was done by Toyota in 1990. As a non SAE member you can buy the paper for $14 or like my local library can get them for free. Check if they can. The SAE technical papers are the best kept secret in racing.

http://www.sae.org/technical/papers/902141