Craigslist CB450 PORTED RACE HEAD

[schaubster]

What do you all think of this? Should I get it?

http://seattle.craigslist.org/tac/mcy/3578477252.html

 

[Tim]

Re: Craigslist CB450 PORTED RACE HEAD

If he's trustworthy and knows what he's doing it's cheap. A proper valve job would cost most of the $240.

But be prepared to add carbs into the mix etc. A ported head isn't going to help with stock cv carbs etc.

 

[crazypj]

Intakes look a bit too shiny for a real 'race' head.
I'm guessing someone hogged the ports out too far then shined it up?

 

[mydlyfkryzis]

The polishing part of a port and polish was proven to be a detriment to flow quite a while ago.....I wonder who polished them?

 

[djelliott]

The polishing part of a port and polish was proven to be a detriment to flow quite a while ago.....I wonder who polished them?

Yep, can cause the fuel/mixture to pool in the intake and cause back flow in the exhaust if they're to shiny aka smooth. You need the bit of texture to keep everything tumbling.

 

[crazypj]

Exhaust port can get mirror finish, the shape, cam timing and exhaust prevent reversion
I leave intakes at 80 grit finish

 

[mydlyfkryzis]

Craigslist CB450 PORTED RACE HEAD

A rougher surface flows better in any situation. Has to do with boundary layers and stuff. It's why fish have overlapping scales. The scales flow better then smooth skin. Sharks have rough surface skin too. Alligators?? Don't know. I stay away from them. Lol


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[crazypj]

I don't know much about fluid dynamics but, because exhaust gas is hot, dry (900~1400deg F) and high pressure, polishing helps prevent heat transference until a layer of carbon builds up
The intake temp is only around 150~200 deg

 

[mydlyfkryzis]

Craigslist CB450 PORTED RACE HEAD

I'll believe that. Not uncommon to compromise one factor to improve another.




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