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Discussion Starter #1


is that type of roughness true for all engines or does aluminum construction make a difference ?
 

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Might wanna knock first...
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normal for any cast and unmachined surface.
 

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Growing up is an option
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...unless they can find "smoother" sand :)
 

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Hold on, we're goin for broke
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Normal for any engine out of the factory aluminum or iron. But it can use some help like you said extrude hone(never seen the results) or port and polish.
 

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Althought it looks like its maximized for flow from the factory, extrude hone and polish wouldnt hurt. Why? When you extrude hone and polish, think of th etwo word/phrases....... Honing and polishing gives you very smooth surfaces, air will flow better along those surfaces than the rouch ones that comes stock.
 

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Extrude hone is done by a course paste that is pressed (extruded) through the ports. This takes the rough parts and sharp corners off the wall, but does not make it too smooth. It is best to do in conjunction with the intake manifold to smooth the transistion between the two. This process requires a special machine.
Porting and polishing is usually CNC'd and finished by hand. Or of course, all done by hand. Polishing is only done on the combustion chamber and exhaust port.
Strangely, a very smooth wall in the intake ports does not aid in flow. And the exhaust would carbon up so quick, it's not normally worth the time involved. A slight roughness is desired to keep the air turbulent and holding fuel vapor. But the roughness in the picture above would slightly benefit from a cleanup.
 

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The two sets of stock heads I have off LSx engines are pretty smooth.

The Intake is plastic so if your pulling the heads get them Port and Polished instead.

Here are my ported heads, intake then exhaust.


 
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