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This is a very touchy topic and i expect everyone to act in a fine manner (this means no "you stupid cunt" "look retard") we are grown men and women respect each other as such. lastly make valid points were all in here to learn, I love to be proven wrong because it means I learned something as to which to I was wrong before. If you have a problem with a post PM the member and consult further or take it up with moderation very simple. I believe no question is stupid unless you learn nothing from that question, their aren't stupid questions, only stupid people who ignore to ask questions.

okay here we go!

Cylinder heads, probably the MOST important and critical part in a engine build besides rods and pistons and block prep. the cylinder head can MAKE or break a engine literally, it can mean the difference between 475rwhp/AWHP/FWHP or 510hp on a dyno. it also means it plays a HUGE role in reliability of the engine and how everything happens. small gains are the key to large success in the long run, at least I believe that. So, the cylinder head port, valve sizing and texture ALL play a major role when trying to squeeze every bit of power out of a engine.

I personally believe that the best way to make power is to rough the surface before the valve this creates turbulence, I believe swirling the port with a nice rough surface will provide the best performance, you further atomization the fuel while also mixing it better with the air for a more efficient combustion/ burn process. flame front becomes more precise as well and it's easier for ignition to occur. the reason I don't believe in polish is because the fuel cannot atomize as well and so it sticks together it makes it harder to burn and it kinda slaps the valve on the way in as well, it doesn't break apart your burn is not as crisp its a lot more richer and harder to ignite, flame front becomes sloppy as well in extreme cases this can also lead to cylinder wash down (this would be a fueling issue though). I believe your not going to out smart a engineer who studies this stuff for a living however I'm explaining why i believe what i believe. if you think out side of the box for a second... it does make a lot of sense, tried to tell a few friends but they were far too close minded to understand they believed polishing to a mirror finish is best for power.

here are some pictures for thought. (to be honest im not 100% sure of picture sourcing but food for though)

1980's F1 turbo head



nascar cylinder head????

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what are your thoughts on this? still believe in the old hot rod mirror polish it best?

additionally anytime you open up a port you decrease your head velocity and increase air mass. decreasing the port size bottle necks the port and you increase port velocity GREATLY and the amount of air being sucked in by the piston through the valve

This post has been edited by s12drifter on Oct 10 2012, 10:58 PM

no one has any kind of input on this at all?

The finish on the port surface really doesn't make an enormous difference till you're nearing the limit of flow. More air = more power. Bigger ports let you flow more air. Smoother ports let you flow more air (but it's not as big a factor as the port size). Smaller ports increase the velocity per unit of flow, which helps with fuel atomization. Of course, when you get into higher revs, the smaller ports will become a restriction, which isn't so good for power.

What's your goal? Is this engine going to be a high revving race engine? Do you want high compression and a very hot cam? Are you interested in a street engine that produces more torque than power and gets good mileage? Take your horsepower target and work backwards. What will it take to get there? Do you want a very broad powerband? You can probably get by with smallish ports. Do you want max power at high revs, but don't care about the powerband as much? You want the shortest, fattest intake track you can produce.

Please mind that this is not intended to disrespect- merely an observation. It's not that people don't have input, I think people are unwilling to discuss this with you because the statements you made above are somewhat abstract and lack rigour. When you ask for thoughtful discussion in your first paragraph, you immediately follow it up with a long rambling paragraph full of incoherent thoughts and phrases. You use the word believe or some derivative thereof no less than 10 times. What you believe is irrelevant. What matters is reproducible results- which are conspicuously absent in your statement. How can we discuss something if we are not given any reliable material to discuss?

Throw abstract at abstract. That's what I did.

Your only talking about the Intake side, but seem to miss the Exhaust side.

A slight rough texture on the intake side helps rough up fuel like you said so that there is not enough smoothness so that the fuel gathers together. But, as always there must be a process of learn by error, As too rough is also bad.

The Debate is whether to leave obstructions or remove them. As many start removing excess valve guide the comes out of the actual valve guide cylinder. So theory is with removing the valve guide excess, one removes a possible blockage. But, then there's the side effect many mention that there's then the possibility of the valves leaning on a angle... How well, Imagine shoving a 2 feet long thin stick through a 5" tube. By the end of the 5" guide, The stick begins to lean towards gravity. But replace the 5" tube with a 1ft Long tube and the stick angles less... I'm Spilling BS by the load, by the way

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The brown part you see before the valve stem, is the excess valve guide. they remove that and possibly some of the hump you see to help airflow.

The other, Is by sharpening between ports of the valve entrance? You supposedly help guide the airflow into the Combustion chamber more smoothly. But there's also debate about this parts and i can't remember it. Think it had to do with heat dissipation being reduced since you just removed some Metal.

The metal that divides the ports is the part I'm talking about, they sharpen it in hopes to help airflow.


On the Exhaust side many agree that a smooth finish ... Polished finish is best so that air velocity is at highest and There's is no... Blockage? Resistance to the flow of air. Also less carbon deposits collect... Well it's harder.

But care must be taken as to not remove...Wait think this is the debate of the reduction of heat dissipation... Well that's all i could muster.

Also there's talks of, Valve angle's , Many say 5-angle jobs are good but i also know of some tuners that just prefer 3-angles... Can't remember why.

I am MR. BS... Thank you for your attention.

This post has been edited by JEV on Oct 16 2012, 05:11 PM