4 stroke head porting question. Removing some of the valve guide?

[trike savior]

I have a lot of experience porting cylinder heads and I have all the dremel and "windy" grinder stuff. My main question is about removing the hump of the valve guide that protrudes into intake/exhaust passage. To remove or not to remove? that is the question. When I first got into porting and doing research it was a very controversial topic, Keep in mind this was with car engines. The one side of the argument is obvious, that getting that chunk of metal out of the way will help flow. But some made the argument that when the valves began to float at high rpm they could become unstable since the guide is now so short and far from the seat, causing premature wear of the valve and seat.

I was not that bold so I always left those areas alone. however on these little motors (200x) that is a really big chunk of metal in the way, so I am tempted. Can anyone weigh in if they have removed the humps and if it has caused any problems, and how long it lasted. thanks in advance.

[trike savior]

but like the Suzuki, wouldn't removing it completely give you the smallest surface area for the air to travel around, ie. just the valve stem

[RIDE-RED 250r]

Just spit-balling with you here and in no way do I profess to be an expert porter. Feel free to tell me I'm wrong if I am..

One thing I would wonder about is unless you open the intake up significantly with a larger carb and probably a pod filter, would you see a real benefit from porting your head beyond a mild degree? You can get the head to flow alot more, but if it's held back by the stock intake tract and carb would it be beneficial?

Second, intake velocity needs to be above a certain level or the fuel can begin to fall out of the intake charge. From what I have learned over the years, you want some turbulence to keep that fuel atomized and suspended in the intake charge so it makes it all the way to the combustion chamber. Opening things up too much can cause a loss of power due to this, correct? Need to keep that balance of flow volume and velocity.

I'm not saying not to do it. Like I said, just spit-balling with you. Again, if I'm wrong feel free to say so.

[Scootertrash]

I'm not an expert port massager (well, maybe in some instances :naughty: ), but this is what I was told:

Remove the casting imperfections in the intake port, but don't polish it. Like RIDE-Red said, you need turbulence to maintain the fuel air mixture.

I use rough grit stones and wheels on the intake side, so the surfaces are rough and contribute to the turbulence of the fuel air mixture. I also match up the intake manifold opening with the cylinder head opening and the carb on the other end of the manifold. All grinding is done on the head and intake manifold for matching up the intake components, never the carb.

I polish the exhaust port so the exhaust can flow out freely. I wouldn't say it's a mirror like polish, but I shine it up good. If it's possible, I also match up the exhaust port with the head pipe.

Now, there may be some here who might criticize me for doing what I do, But I've had good results from what I can tell. Only problem is, there is usually some other mods installed along with the head work so proving the amount of good the head work did is hard to do, but I figure it can't hurt.

I've done it on my trike(s), quads, and my Harleys and never had a negative result.

I did the head work my 200S along with the XR200 cam and a DG exhaust and I can literally walk away from the other 200's and 185's that I've ridden with. Is it just the cam and pipe, or did the head work help? :wondering

The information in this post is worth what you paid for it.




Peace, Love and Grease. ;)

[trike savior]

all good thoughts, thanks. The heads I usually deal with are the 5.0 ho heads which are super restricted on the exhaust side. so you just hog it out as big as you can and enjoy gobs of extra hp. The more mirror the finish on the exhaust the less sediment that can collect over time and the faster you can get the gasses out.

Port matching the intake side will gain you hp no matter what. the smoother you can keep the intake flow the better it is. Never heard of needing turbulence in the intake side but I am used to fuel injection so good tip, thanks. I would just think hitting the back of the valve would create enough turbulence to keep things mixed up.

so scootertrash, did you remove the valve guide humps in the ports or leave them alone?

[Scootertrash]

Nope, didn't remove them, just cleaned them up and around them. I'm with RIDE-RED on that too. I think they help keep things mixed up in the intake tract. Ya gotta keep the fuel and air mixed, and that means keeping the airflow swirling around.

[trike savior]

yeah I did some research and certainly see what you guys mean now on the intake side. one guy actually suggest making a whole bunch of small dimples which seems interesting. he basically leaves the grinding wheel in 1 spot for a second or 2 and repeats it throughout. He does actually suggest grinding some of the valve guide down but not as much as I have seen. I am going to do some more research and will share what I find. maybe we can make a helpful thread here. I was not able to find much searching the site besides who to send it off to.

[trike savior]

want to see some interesting work on the intake side as well as other good ideas, check this out: http://www.allpar.com/fix/holler/head-porting2.html

another good article: http://etonracing1.homestead.com/Two-Stroke-Porting-Technology.html

http://www.popularhotrodding.com/tech/0610phr_cylinder_head_porting/photo_19.html

http://www.cfmmotorsports.com/services/4-stroke-head-porting

I guess I shouldn't be surprised how much the information on this topic has changed in 10 years. this will be fun.

[trike savior]

OK this guys stuff is actually blowing my mind. less intake volume = more hp and he can prove it. however these newer crotch rockets he is working on are more technologically advanced than any of our 30 year old bikes ever dreamed of being. they seem to actually start off too big it seems, which I do not think applies to our bikes. As this guy says, where so many people do a whole bunch of work to a motor; port, cam, high compression piston all at once, and call it a success, who knows what the porting alone did. Holding true to the scientific method can teach you a lot.

http://mototuneusa.com/power_news_--_think_fast.htm

[81Rmachine]

I still have the Audie flow pro sheets to prove it and I can scan them and post them if you'd like to see, but I completely removed the aluminum guide bosses from a 350x head and it was well worth the gain. Many V8 race heads have a bronze guide hanging out in space as Im sure you have already seen such as Brodix for example and I can tell you from experience replacing these sucks because its hard to maintain seat concentricity. However these little honda heads do not need that much aluminum around the guide, there is plenty to support it. The best way to do it is to heat the head, drive the guide out, gring out the guide boss, push the guide back in (if its not wore out), and cut a new valve job. I'm sure your familiar with this on automotive heads and as you know its common on alot of high end drag stuff. Heres a few pics of the head I did. This was worth 12 cfm alone on the intake side with nothing else done.
185357185358185359185360185361

[trike savior]

wow, thanks. that was the exact info I was originally looking for. and your work looks awesome. Now I am rethinking everything I thought I knew about the subject though. Please post anything you can on the subject. I would like to make this a one stop shop for people wanting to try porting their own cylinder head for the first time.

[DohcBikes]

If it comes to porting for the first time, I think trike savior and scootertrash have already nailed it.

To be safe and confident of gains your first time out, port match/gasket match the intake an remove the major to medium imperfections, not too smooth. Exhaust can sometimes be opened up at least moderately, and mirror polish is fine on the exhaust ports, there are even gains from just the polish without enlarging the port.

IMO Its best not to open up an intake too much, or at all your first time on a thumper especially with a stock bore, it just doesn't need the volume.

The method I have had the best gains with on thumpers is to open the exhaust quite a bit and fine polish it. Gasket/port match, and MEDIUM polish, yes I said polish even after I suggested first timers not to, then "golf ball dimple" the intake tract from the opening to about 2/3 of the way in. Works for me.

And oh yeah, my best advice for a first timer, buy an extra head LOL

[barnett468]

I am rethinking everything I thought I knew about the subject though. Please post anything you can on the subject. I would like to make this a one stop shop for people wanting to try porting their own cylinder head for the first time.Wow, ok, fun topic.

As far as porting your particular head, I would suggest doing what 81Rmachine did, however, in addition, if you have a big crack under the exhaust seat like he does, I would fix it.


Without actual flow and dyno comparison tests, it is simply impossible to say for sure what changes do what to what setups etc. What?

The flow required for a certain setup is partially dictated by cam duration, cam overlap, area under the curve, eng displacement and volumetric efficiency etc.. Keep in mind the bikes motoman was working on actually had too much flow for their accompanying parts etc.. There is a threshold where a head can have too much flow. This does not mean that every stock eng has too much or too little flow. Some have just enough. It’s an engine type by engine type based thing. Most stock engines can benefit from mild porting, few can benefit from a reduction in flow like motoman is referring to.

The single biggest area one can gain flow is in the bowls and where the intake takes a curve to the bowls and the valve guides as shown to some degree in 81Rmachine's most xlnt photos. This is called bowl blending and/or pocket porting. Increasing the port size is the second. If one just increases the port size but the air turns into a turbulent mess at the bowl and valve guide etc., it won’t help increase flow much, if at all.

Pocket porting/bowl blending photos.

http://www.moparmusclemagazine.com/techarticles/engine/mopp_0111_porting_the_magnificent_w2/photo_12.html


Ports are rarely modified on the bottom or floor. Doing this can actually reduce flow in some cases.

You can run a small intake port into a large intake port but not vise versa. This is actually beneficial in some instances because it creates what is called a “reversion reduction” area. See more on reversion in the link below. One should never run a port into one that is smaller unless they match the ports so there is a smooth transition from one port to another. If the air runs into a sharp edge, it creates turbulence. This type of turbulence will reduce flow.

Reversion explained.

http://www.circletrack.com/enginetech/ctrp_1008_intake_reversion/



In the 70’s, some porters would polish the entire transfer port on two strokes and some would rough it up slightly. The theories for doing this varied.

Ok, now, there is also some science that states that under some conditions, air flows over a rough surface more smoothly/quickly etc., than a perfectly smooth one. This is supported by the golf ball scenario. Yes golf balls. Why do they have dimples? A smooth ball should fly faster and farther because the smooth surface creates less turbulence right? Bzzz...nope, wrong answer. Ok, this is where I get off the buss, because it has surpassed the limit of my pea brains comprehension, but there is some info regarding this below.

Although I don't understand it completely, if they say so I will not question it. I’ve learned to take some things I don’t understand on faith. Just like E=MC2. Well ok, if you say so, lol.

In the case of a cylinder head, the “shape” of the object referred to below would be the intake and exhaust tracts.

Why do golf balls have dimples?

“At some point, an aerodynamicist must have looked at this problem and realized that the nicks and cuts were acting as "turbulators" -- they induce turbulence in the layer of air next to the ball (the "boundary layer"). In some situations, a turbulent boundary layer reduces drag.

There are two types of flow around an object: laminar and turbulent. Laminar flow has less drag, but it is also prone to a phenomenon called "separation." Once separation of a laminar boundary layer occurs, drag rises dramatically because of eddies that form in the gap. Turbulent flow has more drag initially but also better adhesion, and therefore is less prone to separation. Therefore, if the shape of an object is such that separation occurs easily, it is better to turbulate the boundary layer (at the slight cost of increased drag) in order to increase adhesion and reduce eddies (which means a significant reduction in drag). Dimples on golf balls turbulate the boundary layer.

The dimples on a golf ball are simply a formal, symmetrical way of creating the same turbulence in the boundary layer that nicks and cuts do.

http://entertainment.howstuffworks.com/sports/golf/basics/question37.htm

Ok, this being said, the intake runners on most super high hp cars [includes naturally aspirated carbureted and fuel injected engines and john forces car etc.] are as smooth as glass and have a mirror finish shine, ok.

[atc007]

I still have the Audie flow pro sheets to prove it and I can scan them and post them if you'd like to see, but I completely removed the aluminum guide bosses from a 350x head and it was well worth the gain. Many V8 race heads have a bronze guide hanging out in space as Im sure you have already seen such as Brodix for example and I can tell you from experience replacing these sucks because its hard to maintain seat concentricity. However these little honda heads do not need that much aluminum around the guide, there is plenty to support it. The best way to do it is to heat the head, drive the guide out, gring out the guide boss, push the guide back in (if its not wore out), and cut a new valve job. I'm sure your familiar with this on automotive heads and as you know its common on alot of high end drag stuff. Heres a few pics of the head I did. This was worth 12 cfm alone on the intake side with nothing else done.
185357185358185359185360185361

Love your posts! I am very curious though. How long did that head last with that massive crack in it? Damn shame because that was some nice work!

[barnett468]

The heads I usually deal with are the 5.0 ho heads which are super restricted on the exhaust side.Are you referring to Ford 5.0 heads?

If so, as you probably know, you can always just buy some GT40p's from the junk yard or Ebay, whack off around .025" to get the compression up and call it a day.

[Mickey Dunlap]

*************

[fabiodriven]

A lot of good info there,but there is more to building a good head then just flow numbers. Each engine has it's own needs,not just one set up for all bore sizes,cams and compression ect. Matching it all takes years of testing and building and racing all different combos. First off with out a flow bench you are guest guessing weather you made it flow more. I get more heads in here done by people that did their own heads,or their buddies that does car heads that flow less then stock then I get stock heads in. It doesn't just take someone that has a flow bench, you need to have a engine builder that has built motors like you are building, like Sparks,TC,Powroll or my self to know what will work with what you have and the type of riding your going to do. If it was easy everyone could do it. A simple clean up job is fine if it makes you feel good ,but chances are it won't do you any good,it's just for looks mainly. I tell most of my customers to leave the ports a lone so you don't go backwards,it's safer that way. JMO.

This is what always makes me nervous about porting. I've seen many times where people in the know share this opinion, hence why I've never ported anything.

I don't have much to add other than yes, leaving the intake tract rough is usually a good idea for atomization. I know it's already been said, but that's the only thing I know for a fact.

[trike savior]

I was also afraid of porting when I was first getting started. I was a 17 year old who had no one to show me what or how to do things properly. My dad was a car guy but had no knowledge of this subject. However everything I read on the internet told me I could easily unleash some free horsepower out of my motor because the stock ford 302 5.0 HO E7TE casting was so restricted. I did not have cash to buy another set of heads, which added more fear because I had to work with what I had and if I screwed it up I was done. took my time and did as much research as I could. On those motors there was nothing to do on the intake side. the intake manifold runners were significantly smaller than the cylinder head passages so porting the head bigger was pointless. And an aftermarket manifold was not even a possibility at that time. however I smoothed the intake runners so nice which now I see was not the right thing to do. Im lucky it was fuel injection and the injector sprayed directly at the intake valve. if it was carbeurated or TBI I would have been screwed.

The exhaust side was where all the careful work was at. making sure each one was the same as the last one. I went a little bigger than a stock gasket because the cheap set of headers I was able to afford were bigger than that. and I smoothed it all to a mirror finish as well.

No other work to the motor besides the port and headers and everything else was stock. I even had to reuse the stock h pipe for the time being. But wow what a difference. It gave my heavy 1991 Lincoln Mark VII (7) with 300 lbs of stereo weight in the trunk, the ability to break the rear end loose at the tap of the throttle. And I could just shred tires in a parking lot when I felt like it. Before I had to brake torque to get them loose. then once my friends saw what I could do it was "here do mine." come to think of it I guess im lucky everyone I did had multiport fuel injection.

SO I TOLD THAT STORY TO ASK THIS. Can anyone disagree with the idea of "go as radical as you want on the exhaust side but moderate cleaning and increases on the intake." it seems there is sufficient evidence for needing flow and velocity on the intake side. is it correct to assume the bigger the passage way to get the exhaust out the better. all my research so far has yielded nothing about the exhaust side of things.

(P.S. now that I have my 351 W roller cam block my plan is to build a 408 clevor, Cleveland heads on a Windsor block. but don't peg me as a Ford guy. I grew up with and love Corvettes too. there are 4 in the family. they make me itchy though.)

[Mickey Dunlap]

*****************

[81Rmachine]

"As far as porting your particular head, I would suggest doing what 81Rmachine did, however, in addition, if you have a big crack under the exhaust seat like he does, I would fix it."

I was waiting for someone to point that out LOL! This particular head was simply for R&D.
Barnett, great info on airflow! I couldn't have said it better myself! The only thing i can add is that on the topic of attached airflow and turbulence, it is also important info when cutting your seats. Your standard 3 angle valve job is as you know a 45 deg seat angle, a 30 deg top angle, and a 60 deg bottom cut. A 5 angle would add a 15 to the top and a 70 or 75 deg to the bottom depending on the specific head and bowl configuration. It is very important not to use anymore than a 15 degree change between angles as this WILL break the boundary layer and the air will go turbulent drastically reducing airflow.

I'm glad you brought up the golf ball surface as you might already know Rottler Mfg. has patented this surface finish with their cnc porting machine. The grooved tool paths most cnc machines leave perpendicular to flow is very effective in creating a very large boundary layer. This as barnett mentioned prevents any chance of air going turbulent and is very helpful in a cylinder head such as your standard 23 deg wedge sbc. In this instance the air has to essentially navigate a 67 degree turn as the port virtually starts on the deck surface and the air is much more likely to stay attached to the SSR (short side radius) and not go turbulent.

185435

[barnett468]

It gave my heavy 1991 Lincoln Mark VII (7) with 300 lbs of stereo weight in the trunk, the ability to break the rear end loose at the tap of the throttle.Once again, great thread, great info. I have an 85 town car with a 302, lol.





SO I TOLD THAT STORY TO ASK THIS. Can anyone disagree with the idea of "go as radical as you want on the exhaust side but moderate cleaning and increases on the intake." is it correct to assume the bigger the passage way to get the exhaust out the better. ...all my research so far has yielded nothing about the exhaust side of things.

From post 14.

Without actual flow and dyno comparison tests, it is simply impossible to say for sure what changes do what to what setups etc. What?

The flow required for a certain setup is partially dictated by cam duration, cam overlap, area under the curve, eng displacement and volumetric efficiency etc..This includes the exhaust side.





(P.S. now that I have my 351 W roller cam block my plan is to build a 408 clevor, Cleveland heads on a Windsor block. but don't peg me as a Ford guy. I grew up with and love Corvettes too. there are 4 in the family. they make me itchy though.)

You might like the article below, it gives a bit of info regarding intake vs ex flow and thermal coatings etc. Might also give you ideas for your Clevor build.

Joe Sherman, 800 hp 9000 rpm 374 stroker on a 302 block. Booyah!

http://www.hotrod.com/techarticles/engine/hdrp_0607_joe_sherman_built_ford_windsor/

[Mickey Dunlap]

*****************

[DohcBikes]

I'm glad you brought up the golf ball surface

Why thank you, since I did mention it first :D...something I learned about in performance engine building/dyno class at MMI. It was really nice being able to dyno and flow bench different head setups on different bikes.

More flow didn't always make more power, just as has been mentioned. And thanks to everyone for providing the more technical stuff that I don't fully understand....yet, but I'll keep reading.

[barnett468]

Why thank you, since I did mention it first :D...

From post 13.

then "golf ball dimple" the intake tractYes you did, I read every post on here before posting and either missed it or forgot about it [cause I'm old] while I was typing my post, otherwise, I would have acknowledged you for first mentioning it and therefore I apologize for the oversight.

That being said, I [not you, lol] am the one that posted some detailed info on the subject which contained cool big words I barely understand like, "TURBULATORS", "LAMINAR FLOW" and AEROPHYSICS" etc..

Perhaps Tiger Woods's ex wife was simply trying to improve the laminar flow over his head by liberally applying aerophysics to it with the now infamous golf club [now for sale on Ehay] by "Turbulating" it.

:beer

[DohcBikes]

That being said, I [not you, lol] am the one that posted some detailed info on the subject which contained cool big words I barely understand
On the other hand, I did not fail to acknowledge the explanations......;)


And thanks to everyone for providing the more technical stuff that I don't fully understand....yet, but I'll keep reading.

Trike Savior, post below is heard, understood, acknowledged, thanks...no problem here.

[trike savior]

I posted this site on an earlier post. any thoughts on this guys intake port design? http://www.allpar.com/fix/holler/head-porting2.html I can make a tool to do that pattern a lot easier than sitting there making dots for hours.

also farther down he shows making the groove on the flat part of the combustion chamber which I have heard other places is a good addition. any thoughts?

I am a fan of smoothing and polishing the combustion chamber and removing any sharp edges. that was 1 other thing I did to the heads on the ford. after 30,000 miles when I removed motor for my more modified motor I noticed barely any carbon build up in the combustion chamber. any arguments for or against?

and gentlemen. can we please not turn this into an "I said but you said". keep it clean so people don't have to look through crap to find info. just figured id say something right away before it goes too far. I really want this to be a plethora of info for people wanting to try this.

[DohcBikes]

Excellent mention of smoothing the combustion chamber, I have never done this, does anyone have any good tips for a first timer on that?

[barnett468]

On the other hand, I did not fail to acknowledge the explanations......;)Hey, I confessed so give me a break...I'm almost a senile citizen. Just wait a while, you'll get old too, old too, old too...and start forgetting, but because you are forgetting, you will have forgotten that you forgot and you will think that everything is just fine.

Ok, now grab a beverage and check out the vid below. No, it's not one of those.



Below is a video I thought might be interesting to some. It is of a before and after flow test of modified seats/bowls, but no “tunnel” work, on a 4 valve single cylinder motorcycle head.

The intake seats AND bowls were worked on but only the seats were worked on, on the exhaust.

First of all he is missing one test line on his graph for some reason.

Notice that on the exhaust port he gained 0 flow from 0 - .100 lift, and actually lost around 7 cfm of flow from .100” -.350” lift and from 400 to 600 he gained around 7 cfm.

On the intake side he lost 100 cfm from 0 – .250 at which point he gained around 15 cfm up to .600.

For whatever it’s worth his intake bowl is ground slightly rough.

There is little to no intake flow going on during the lower lift of the intake valve due to pressure from the last of the exhaust stroke trying to push exhaust gas back into the intake. This is because both the ex and in valves are open during this phase. This is caused by the overlap of the in and ex lobes on the cam.

If one were to assume that this head had the ideal flow from the mfg. for a cam with .325” – .400” lift, then what this particular port job would do is LOOSE power throughout the entire rpm range of the engine, lol. The high performance cams for an ATC350X from web cams are from .350”- .392” lift.

As some others have suggested, doing anything other than just a minor clean up may have adverse effects on performance.

http://www.youtube.com/watch?v=ycrm5We06Mg



PS - You could have at lest told me my Tiger Woods joke was funny. Oh btw, I suddenly seem to have forgotten where those Holley and Ford main jet vs inch size charts are that you wanted.

[barnett468]

Excellent mention of smoothing the combustion chamber, I have never done this, does anyone have any good tips for a first timer on that?One way is to do it with a small red scotch brite pad on a rubber backed attachment for an air gun.

[barnett468]

I posted this site on an earlier post. any thoughts on this guys intake port design? Since the texture of the ports affects both flow and fuel atomization, simple flow tests will not give a full picture of the affect of these different textures etc., therefore, in addition to what I mentioned earlier, before and after dyno tests are also helpful to determine what affect theses changes really make.

If you roughen up a surface, you “might”, in some cases, reduce flow, however, a rougher surface theoretically should atomize the fuel better up to a certain threshold.

You can reach a level of turbulence that reduces velocity, and since the higher the velocity, the more the fuel is atomized, it would be a trade off to some degree, but again, without proper, thorough testing [or unless one is an aerophisicist], it is pure speculation imo.

If I were to speculate, I would say that his ports are way too rough. Part of this speculation is based on the fact that I have seen hundreds of stock, and ported heads, and I think it might have been discovered a long time ago and used if it was beneficial.

That being said, I for one love testing new ideas, but I wouldn’t grind up a set of my own heads to test it on.





farther down he shows making the groove on the flat part of the combustion chamber which I have heard other places is a good addition. any thoughts?

I am a fan of smoothing and polishing the combustion chamber and removing any sharp edges. that was 1 other thing I did to the heads on the ford. after 30,000 miles when I removed motor for my more modified motor I noticed barely any carbon build up in the combustion chamber. any arguments for or against? From what I can see, the grove he is installing does not seem like it will create a hot spot that might cause pre ignition, therefore, I don’t see anything negative occurring from it. I am a believer in polishing the combustion chamber. One could polish it AND add the groove if one wanted.


I found the following and posted it on the thread below. It’s a different idea then the one in the link.

2 STROKE CYLINDER HEAD “TURBO” CUTTING

“Trinity tried to think outside the box for a while with cranks and their heads as well.....They still to this day turbo cut the head. I have a head on my bench that is an early model done by JD i believe when they were doing the R&D.

In THEORY it was to create a funnel reaction that would focus the fuel to the spark plug.....Notice how the cuts turn and angle to the plug. Trinity still does this I believe but they have perfected it by using the CNC or another type of non-human method.”

http://www.3wheelerworld.com/showthread.php/163970-84-Tecate-Crank-Stuffing-and-Rebuild-w-pics?highlight=turbo

[DohcBikes]

One way is to do it with a small red scotch brite pad on a rubber backed attachment for an air gun.

I do have the 3M rolock style red pads..... if I were to polish for example a 200x combustion chamber, assuming I only polish and do not remove any measurable amount of material, so as not to increase the cc of the chamber, would that normally be a good thing to do whenever I'm rebuilding an engine, or only with certain setups?

[barnett468]

I really want this to be a plethora of info for people wanting to try this. I am a fan of smoothing and polishing the combustion chamber and removing any sharp edges. that was 1 other thing I did to the heads on the ford. after 30,000 miles when I removed motor for my more modified motor I noticed barely any carbon build up in the combustion chamber.

any arguments for or against?

I do have the 3M rolock style red pads..... if I were to polish for example a 200x combustion chamber, assuming I only polish and do not remove any measurable amount of material, so as not to increase the cc of the chamber, would that normally be a good thing to do whenever I'm rebuilding an engine, or only with certain setups?My opinion, based on personal experience and reading etc., is that polishing the combustion chamber on a cylinder head has no negative effects and only positive ones.

It is more beneficial on chambers with a rough surface such as cast iron automotive heads.

Since most of the chambers on aluminum heads are already pretty smooth, the biggest benefit from polishing them is to reduce the potential for carbon build up.

I have not seen any proof [dyno charts] or even claims that prove or suggest this process increases hp or torque etc., therefore, if that is your goal, I wouldn’t expect any, others might.



PURPOSES FOR POLISHING CYLINDER HEAD CHAMBERS

As you likely know [but some others may not], two of the reasons for polishing a combustion chamber are to reduce carbon build up on the chamber, and to reduce/eliminate the potential for "hot spots" which can be created by “sharp” points which can heat up enough to cause preignition. Preignition is different than detonation and is a very bad thing in a gasoline engine but is a controlled event that is required [per se] in a diesel engine. Diesel engines are designed to withstand the effects/byproducts of preignition.

If one has ever had any vehicle that continued to run [usually briefly] after the ignition was turned off, it is due to preignition [not detonation], irregardless of the type of fuel being used. This process/effect is commonly referred to as “dieseling” or “run on”.

We had one gas engine [60’s Ford V8]that continued to run [albeit badly] at idle, and also a bit under throttle, for 10 minutes until we felt bad enough for it that we put it in gear to stop it tereby putting it out of its misery. Please don’t do this to your own engine, lol.

Preignition is different than “detonation”. See some info in link below.

http://en.wikipedia.org/wiki/Engine_knocking



SOME POLISHING TOOLS AND TECHNIQUES

For polishing aluminum or steel, in addition to Roloc Scotch Brite pads. Sanding rolls can be used prior to the final finish. Some then use small sanding “flappers” then finish off with “cross buff” pads. The sanding rolls and cross buff pads require a tapered spiral mandrel. Carbide bits are used for cutting only and not for polishing. Others may use other tools for polishing.

Below are a couple of short videos I thought might interest some.

Cylinder head chamber polishing.

http://www.youtube.com/watch?v=1TLExYc7I14


Porting and polishing tools.

http://www.youtube.com/watch?v=N7xmKQ0_H7A


Cross buff pads.

http://www.google.com/search?q=cross+buffs&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a



THERMAL BARRIER COATINGS [Performance improvers]

For a combustion chamber finish that does improve performance, I suggest one researches thermal barrier coatings. See some info in the links below.

"EPC 108 - This combustion chamber coating is applied on the piston crown, valve face and stem, and exhaust port and chamber. This thermal barrier process reflects heat into the combustion chamber, which increases exhaust gas velocity and greatly improves engine scavenging potential."

http://www.embeeperformance.com/piston-coating-thermal-barrier-faq.php


More coating info and “test” results from another coating mfg.

http://swaintech.com/category/automotive-coatings-articles/


Article excerpt from link I previously posted.

“Joe Sherman believes engine coatings can add upwards of 15 to 20 hp on a high-end engine. Embee Performance Coatings applied thermal-barrier coatings to the headers, exhaust ports, valve faces, cylinder-head combustion chambers, and piston tops. The piston sides also received antifriction coatings, as did the main and rod bearings. Oil shedders were applied to the crankshaft and connecting rods. Sherman also had the piston pins hard-chromed for reduced friction.”

http://www.hotrod.com/techarticles/engine/hdrp_0607_joe_sherman_built_ford_windsor/


Photo of thermal coating on combustion chambers and valves.

http://www.hotrod.com/techarticles/engine/hdrp_0607_joe_sherman_built_ford_windsor/photo_01.html#photo_08.html?&_suid=139117271588008459596559831634

[El Camexican]

Years back I had the pleasure of riding a 900SS Ducati in stock trim and then again after having the heads done by these guys http://extrudehoneafm.com/ the difference was impressive.

[DohcBikes]

Great link El!! I was very curious about the process so I checked it out in the FAQs, hope no one minds if I copy and paste their explanation......

"In the Extrude Hone process, two vertically opposed cylinders extrude abrasive media back and forth through the passages formed by the workpiece and the tooling. Abrasive action occurs wherever the media enters and passes through the most restrictive passages.
The basic elements in the process include:

the Tooling, which confines and directs the media flow to the desired areas of the workpiece
the Machine, which holds and dispenses the media, and controls the media extrusion pressure, along with flow volume
the Media, which determines the pattern and aggressiveness of the abrasive action that takes place in the workpiece.
By selectively permitting and blocking flow into, out of, and through the passages in the workpiece, the tooling can be designed to provide media flow paths through the workpiece that restrict flow at the areas where deburring, radiusing, and polishing are desired. Frequently, multiple passages and/or parts can be processed simultaneously.
The consistent media slug length through all the cross holes in the cylinder pictured to the right demonstrates the uniformity of the Extrude Hone process. Normally, tooling also contains the flow of the abrasive media to direct it between the extrusion cylinders of the machine.
A typical Extrude Hone machine has two vertically opposed media cylinders that extrude the media back and forth through the passages formed by the workpiece and the tooling. The cylinders separate, for insertion or removal of the workpiece/fixture, and clamp together to seal during processing."

So cool!:beer

[El Camexican]

The odd (to me) thing about the heads they did for my buddy was that although they were smooth as glass they weren’t uniform. There were some dips and humps (very slight) in the ports. I don’t know if CNC porting advances have surpassed the gains this process makes, but 20+ years ago when the Ducati was done the NASCAR and F1 teams were supposedly doing their heads by hand to the best of their abilities and then sending them to Extrude hone for the final finish. As you likely read this process only takes 1mm or so off the base material, so while it can make a stock head run better it is not going to turn it into a race only item.