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i replace my engines intake rubbers (between the carbs and the cylinders) lucky me to find a hack job porting. am i losing power from a choppy port job on my xs400 from a previous owner? the concept was achived but its rough. (gouges around the opening and some nicks further in) had pics but they didn't come out clear enough to illustrate it.
 

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Tough to say. One important area is the transition from the rubber manifold to the intake port. That should be smooth. As far as noticeable performance gain or loss from irregular surfaces in the port, I think unless you're racing, you won't feel a difference. Particularly on an engine that size, there are lots of things that you can do to improve performance, but porting alone won't make that much difference.
BTW, I've taken out minor imperfections with a dremel without removing the head, just stuffed oily rags below the area to catch any metal and smoothed out the area in question, including the above mentioned transition area.


FR
 

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quote:Originally posted by coreyjdl

what scares me are the nicks around the port and further in, i doubt the head was initially removed for the port job.
It was probably one of my early attempts!

Kidding, yeah anyway, you have to think like you're a dentist when you do that stuff, but if you take your time and set up the job properly you can smooth it out. Or just leave it, as I said, I doubt you'll have any detrimental effects.

FR
 

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The guy that did my head ( Mike Rich) said that some texture to the intake and port are a good thing. Keeps a thin turbulent layer next to the walls to prevent fuel dropping out of suspension in a laminar flow layer. Kinda like the dimples on a golf ball, or the dimpled surface of some aircraft wings, overall it lessens resistance to flow I guess.
Not sure it that would apply to gouges etc. :)
JohnnyB
 

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wish we could put a fish-scale texture on these flow sensitive surfaces. fish (and birds) figured out how to smooth flow over surface before we were born. any one hear about the new swim suits? some records are going down this summer in bejing thanks to this kind of attention to surface. unless they can't breathe the air.
-parks
 

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What Branson said, the days of mirror polished ports are over. I've seen CNC done stuff that looks sorta like, now that you mention it, fish scale tool marks.

I'm not familiar with your head, but if you don't think it was pulled to port it the chances of it being catastrophically screwed up are small(IMHO). Most heads the flow restriction is the valve guide boss area and the bowl directly under the valve. Typically the inlet of the port flows plenty and is a little lazy velocity wise anyhoo. Unless he went crazy enlarging the inlet chances are you motor won't know the difference bad or good.
 

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Hmmm....fish scales...and like birds feathers. Natures anti-reversion, someone should do some research on this stuff as it relates to pulsating flow of gases and fluids (as if someone isn't already).
Just think, a fish scale like surface on a gas system that has any reversion pulses....if you could reduce inefficiency of flow just 5-10% it would be huge for industry.
JohnnyB
 
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