Aluminum polishing compound

[gale]

I would like to polish the inside of my intake/exhaust ports in my head after I finish the port work. Any suggestions on a compound that I can use?
Cheers
Andrew

[n xntrx volvo]

rubbing compound.

[the poi]

tripoli, then white rouge if you're out of your damn mind.

[Chris_R]

You don't want to polish the intake ports anyway - something to do with laminar flow and fuel puddling... Polished exhaust is cool. Get some flap wheels in various grits, then what the poi said.

[ckanderson]

Yea^ polished intake ports dont tumble the air, also air doesnt flow as well over smooth surfaces as it does on rough ones.

[footScoot]

Polished the intake manifold ports on a small block Chevy once, didn't run for crap, had to remove the intake and have the ports sandblasted. Ran fine after that. Live and learn.:nod:

[the poi]

Yea^ polished intake ports dont tumble the air, also air doesnt flow as well over smooth surfaces as it does on rough ones.

This wrong. Air flows much smoother on smooth surfaces. The problem with a polished intake port is with fuel droplets from a carb (or poorly atomizing injector) will stick, bead up, and than fly off. It makes for inconsistent fueling. The rough surface will allow an amount of fuel to coat the surface, so additional droplets will quickly spread out into the mass, while vaporization removes it, very consistently. So on an injected car thats blasting fuel onto the back of the intake valves, its not that big a deal. But for that matter, polishing either port isn't really worth it either...you can get it "smooth enough" with fine sanding...

[quinn_volvo]

This wrong. Air flows much smoother on smooth surfaces. The problem with a polished intake port is with fuel droplets from a carb (or poorly atomizing injector) will stick, bead up, and than fly off. It makes for inconsistent fueling. The rough surface will allow an amount of fuel to coat the surface, so additional droplets will quickly spread out into the mass, while vaporization removes it, very consistently. So on an injected car thats blasting fuel onto the back of the intake valves, its not that big a deal. But for that matter, polishing either port isn't really worth it either...you can get it "smooth enough" with fine sanding...

.

[ckanderson]

^im not here to argue, but it has been proben that on a smooth surface air forms a "boundry layer" of stagent air, unfortunetly I cant find the proper article via google, but here is a link to the boundry layer phenominom in relation to golf balls flight.

http://www.sciencebuddies.org/mentoring/project_ideas/Sports_p012.shtml

you mention that air flows smoother on a smooth surface, this is true, unfortunetly smoother doesnt mean better flow. beacuse of the boundry layer thier is less flow.

Here is an excerpt from "metric Mechanic" these guys are well known BMW engine builders.

Porting the HiFlo Head
We take porting very seriously. This is an area where you can pay out a lot of dollars and get nothing. For example, polishing ports will net you NO air flow gain but it will cost you, on an average, $50-$75 a cylinder ($200 -$300 for 4 cylinder and $300 - $450 for a 6 cylinder. We don't waste time polishing parts but we do texture the surface of the port by glass beading. We port quite differently. We have developed master cutters that take the guess work out of porting. These master cutters were developed from extensive flow bench testing. They have multiple shapes and angles. Using these cutters helps us to produce very high repeatable results. Port flow deviation is typically less than 1%. Some hand work is still needed but it is reduced to a minimum.

After inspecting and cleaning, we machine Surface Turbulence grooves in 150 - 200 valves at a time.

And here is the link to the page

http://www.metricmechanic.com/catalog/Cost-cutting-measures.php

[the poi]

the boundry layer phenominom in relation to golf balls flight.

Golf balls are dimpled not to smooth airflow, but to seriously disrupt it. The disruption produces a turbulent boundary layer, as mentioned in that link, and by doing that, the seperation is pushed all the way around the ball. Essentially, there is less "suction" behind the ball. Thats a sphere moving through a fluid, for our pipe flows (an intake port), a smooth wall is the best for airflow.

edit:// and the metric mechs are saying what I said above, polishing ports just doesn't do anything in the grand scheme of things, the returns aren't worth the effort