Smooth v.s. Rough

[smokin]

Ok now I have a question.I am in the middle of building my motor right now and I was thinking.Would it be better to be rough/beed blasted inside the manifold or smooth/polished. I have heard that rough atomizes the fuel better and if you make it smooth it will hurt the performance.Now other people say that smooth is better for flow and makes more power.

I'm on the smooth side of the arguement but am not sure. I have never had two manifolds to compare,so rough or smooth???(At the moment mine is smooth and I was planning on keeping it like that but I want to see what people opinions are on the matter)

[scooterconvert]

I've never heard of someone bead blasting a head for that purpose. This doesn't mean that it hasn't been done, but I would tend to think that the smoother the surface the better, since this is a popular mod for car engines.

[XPS1210]

not the head... the intake manifold...

I'd think smooth for better and easier flow... however I know lennox said that was incorrect last time I posted that...

I got a performance manifold on my scooter... and it's fairly smooth... but there are edges and such that I think would hinder the flow of fuel... but that's how it was designed..?

[Lennox]

I would tend to think that the smoother the surface the better, since this is a popular mod for car engines.

keep in mind that the people who do this to their cars have FUEL INJECTION!

Smokin, the inside of your cases in rough, right? Ever wonder why? Atomization, my friend!

I would recomend smoothing out any casting/ROUGH edges on the intake. Polishing it is not necesary, neither is bead blasting it.

In fact, I think the difference is SO minor that you probably couldn't tell either way....... it is mostly just in "theory".

[smokin]

I figured rough would be better for atomization but,Your saying that when smoothed out it would be such a Minor gain,so I will just leave it smooth.Still a gain it will add up with the rest of the minor things I'm doing. :naught: Thanx for your opinions on the matter.

[cant drive 55]

I was watching TV last night and I saw that they were changing the manifolds on this guys Honda 125cc dirtbike. They changed out the stock one and put in a new one that was machined with these grooves in it. They said that it make the engine run smoother because it does atomize the fuel better.

Supposedly it creates some sort of tornado vaccum inside also which helps it to flow better.

You guys are probably right though in that it makes such a small increase in performance that you wouldn't notice it.