help on porting and polishing

[PsychoX]

ok if anyone knows anything about porting and polishing the head help me out here please.... i recently P&P my head on my 200x the intake and exhaust , and i was wondering i have heard two different things... on the intake side i have heard to not polish it b/c the gas needs the ruffness to mix right or somthing on that sort, but i have also heard to polish the intake b/c it will flow better if anyone knows if i should polish it or not please help me out ...thanks

[TeamGeek6]

The carb and cylinder heat do the mixing, any contact that the A/F charge makes with cylinder walls or the head is bad, because they are relatively cold. The charge needs to be hot.

Porting is about getting better airflow, removing restrictions around valve seats and the spark plug nose, even back into the intake manifold. The problem is knowing whether the grinding did anything useful. It's hard to put metal back once its removed.

Any restriction that causes fuel to be knocked out of mixture is bad, that causes fuel droplets or puddles that load up the cylinder and make it misfire. Again, hard to know what works. Either you have lots of trial and error, or a flow bench. A flow bench isnt that hard to build but it takes a few $$$

I approach proting by imagining a particle of fuel moving thru the system at various valve openings, especially at low lift when the A/F charge tries to come out of the valve seat sideways. Fer example, the GL1200 Goldwing heads have serious ridges around the valve seats that restrict flow half way around the valve at low lift. A few hours with a grinder made a huge difference. There was also a hump near the spark plug that shielded the electrodes when the plug was at certain angles, that was also ground away. After that and cc'ing the domes, plus some carb and ignition magic, it burned the back tire 60' in 2nd gear on a stock engine.

Polishing does more than affect flow, it does things with heat losses (efficiency) and carbon buildup, plus some exotic electrical effects I wont get into. Its generally a good idea to have things polished nice and smooth, especially pistons and rods to reduce stress cracks.

There is some truth to roughness making better flow. The Russian MIG fighters had small divots put in the fuselage ahead of the air intakes to increase flow into the engine. A motorcycle drag racer in Cincinnati told me they got some gains by pockmarking their carbs and intakes, he assumed they filled with fuel and were somehow smoother. I have no idea.

[PsychoX]

ok well thanks for the help but just to make sure... lol should it be smooth or some what ruff

[3leggeddog]

definitly smooth,hints the name port and POLISH.polish that biatch smooth

[NOS_350X]

The exhaust you want poslished, as smooth as you can get it.

The complex part comes in the intake, some say that you want it rough, spirolled, and polished. Its all a matter of oppinion. I belive that if you want a even pull throughout the engine make the intake ports larger and keep it rough. If you just want straight power and dont care if its got a flat spot on the power the polish it. Every bike ive rode with polished intake has a huge flat spot right in the middle rpm's. With spirolled porting some use it because it can flow faster (air flows faster in a spiroll than in a strait lines hitting walls.) Each type of porting has its own theorys on why to do it but its all your decision on how you want it.

I say use your own physics knoledge and decide for yourself


My preference is roughed up a little.

[PsychoX]

well thanks for all the help except that crazy **** 3leggeddog haha no im just playin but B we deff wanna go riding sunday and derrick wants to go up to galion and hit up the track for some prac. and i know charlie will be up for it... PLUS i gotta get down the down hill and up hill doubles lol so ill get ahold of ya this weekend but yea thanks everyone again for the help

[conig]

just throwing in some hear say so feel free to disregard it.

A local engine builder to me swears by polishing smooth and then glas beading the surface for super tiny divets, think if a golf ball is his theory. It also makes it to were you can hardly tell a motors been ported if your racing.

[hotroddal]

well i dont know if this is a good idea or not, but a guy i know uses a dremal tool with a sanding bit on it and smoothes out the inside of both the intake and the exhaust ports.