Port and polish worth it?

kazin1111 · 02-25-2009, 05:09 PM

anyone get a port and polish done on a BT? is it safe to take to any machine shop or is there a guru i need to ship my head to? prices? whp gain? estimated gain if I upgrade the cams?

ebouwman · 02-25-2009, 06:41 PM

thing is that the more you mess with cams and everything, the more that porting will pay off.

That said, it doesn't do that much for you. I had it done while i had my head in the machine shop, but i wouldn't take the head off just for that, and i wouldn't ship it go get done.

But as for before and after i could really see the difference in the head of my 4age, they took off a LOT of sharp edges and stuff. But i'm not totally sure i feel it in my car, mainly it has other problems, like the t-vis not working, and the fact that it's an automatic. If you have the head off then why not, as long as you have the money.

I believe you can get quite a gain from doing the cams though, and if you're spending that much you might as well shell out to get the head ported.

EDIT: I have the stock 4age, the bluetop

delgato · 02-25-2009, 07:40 PM

Kazin111

I am porting my head right now.
Is Port/polish worth it? Well it does give gains of course as long as you do not screw up the flow. I tend to "port" only by cutting off sharp edges or burrs, seams get smoothed. Little chance of messing up the flow that much.
Polish by going from 80-120-240-320 grit. The intake should not be polished, per se, but the exhaust you can go all out. I tend to run out of steam and do not go mirror smooth. Back to the intake, its best to keep a certain very slight roughness to increase surface area, which encourages fuel/air swirling. So I keep it at 320grit. For the mirror smooth exhaust you need compounds.

To do this easily yourself you need an air comp, a Harbour freight $15 die grinder and 1 long Eastwood mandrel (~$5) and sanding cartridges ($6 ea for 10 ea) from 80-320. Also, BUT not necessary are aluminum cutting bits. This takes out the big chunks but the BT head does not have much of that. Pretty clean head, but still needs cleaned up.
Afterward the seats need AT LEAST lapped, possibly ground. I do not have the tools for that so I am super careful. (I do lapp though) So far I have been lucky not to accidentallygrind the seats.

I will post some photos later of my port/polish and the tools I use.
Its really not hard so much as you just need patience, tools and time.

ebouwman · 02-25-2009, 07:48 PM

The reason for leaving the intake smooth is a different story from different people, basically what i understand is that leaving it rough is like leaving the dimples on a golf ball. So what it's doing is letting the air move more smoothly. Rough surface creates a smooth flow? Kind of counter intuitive but it does.

My machine shop glass beaded it to make it rough, i'm not totally sure what that is, but i think it's like sandblasting but with glass beads, but it left a nice finish

I||ICIT · 04-21-2009, 03:56 AM

rough(ish) intakes are also left rough to encourage any fuel that settles onto the manifolds to be drawn back off by the incoming air. ensures a proper mix and good vaporisation and avoids large "drops" of fuel being drawn into the cylinder, they dont burn well.

AW11Drifter · 05-03-2009, 05:56 PM

My machine shop specialist tells me that the 20V ST or BT head are already high flowing so Port and Polishing doesn't do much of a difference unless you do supporting mods as well.

02-25-2009, 05:09 PM	#1 (permalink)
kazin1111 Weak Skills Join Date: Feb 2008 Posts: 122 Thanks: 11 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	Port and polish worth it? anyone get a port and polish done on a BT? is it safe to take to any machine shop or is there a guru i need to ship my head to? prices? whp gain? estimated gain if I upgrade the cams?

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02-25-2009, 06:41 PM	#2 (permalink)
ebouwman Curve Hugger Join Date: Jan 2009 Location: BC, Canada Posts: 1,388 Thanks: 18 Thanked 48 Times in 48 Posts My Google Map iTrader Rating: (0/0% )	thing is that the more you mess with cams and everything, the more that porting will pay off. That said, it doesn't do that much for you. I had it done while i had my head in the machine shop, but i wouldn't take the head off just for that, and i wouldn't ship it go get done. But as for before and after i could really see the difference in the head of my 4age, they took off a LOT of sharp edges and stuff. But i'm not totally sure i feel it in my car, mainly it has other problems, like the t-vis not working, and the fact that it's an automatic. If you have the head off then why not, as long as you have the money. I believe you can get quite a gain from doing the cams though, and if you're spending that much you might as well shell out to get the head ported. EDIT: I have the stock 4age, the bluetop

02-25-2009, 07:40 PM	#3 (permalink)
delgato No Skills Join Date: Jan 2009 Location: USA Posts: 13 Thanks: 5 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Kazin111 I am porting my head right now. Is Port/polish worth it? Well it does give gains of course as long as you do not screw up the flow. I tend to "port" only by cutting off sharp edges or burrs, seams get smoothed. Little chance of messing up the flow that much. Polish by going from 80-120-240-320 grit. The intake should not be polished, per se, but the exhaust you can go all out. I tend to run out of steam and do not go mirror smooth. Back to the intake, its best to keep a certain very slight roughness to increase surface area, which encourages fuel/air swirling. So I keep it at 320grit. For the mirror smooth exhaust you need compounds. To do this easily yourself you need an air comp, a Harbour freight $15 die grinder and 1 long Eastwood mandrel (~$5) and sanding cartridges ($6 ea for 10 ea) from 80-320. Also, BUT not necessary are aluminum cutting bits. This takes out the big chunks but the BT head does not have much of that. Pretty clean head, but still needs cleaned up. Afterward the seats need AT LEAST lapped, possibly ground. I do not have the tools for that so I am super careful. (I do lapp though) So far I have been lucky not to accidentallygrind the seats. I will post some photos later of my port/polish and the tools I use. Its really not hard so much as you just need patience, tools and time.

02-25-2009, 07:48 PM	#4 (permalink)
ebouwman Curve Hugger Join Date: Jan 2009 Location: BC, Canada Posts: 1,388 Thanks: 18 Thanked 48 Times in 48 Posts My Google Map iTrader Rating: (0/0% )	The reason for leaving the intake smooth is a different story from different people, basically what i understand is that leaving it rough is like leaving the dimples on a golf ball. So what it's doing is letting the air move more smoothly. Rough surface creates a smooth flow? Kind of counter intuitive but it does. My machine shop glass beaded it to make it rough, i'm not totally sure what that is, but i think it's like sandblasting but with glass beads, but it left a nice finish

04-21-2009, 03:56 AM	#5 (permalink)
I\|\|ICIT No Skills Join Date: Feb 2009 Posts: 45 Thanks: 22 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	rough(ish) intakes are also left rough to encourage any fuel that settles onto the manifolds to be drawn back off by the incoming air. ensures a proper mix and good vaporisation and avoids large "drops" of fuel being drawn into the cylinder, they dont burn well.

05-03-2009, 05:56 PM	#6 (permalink)
AW11Drifter No Skills Join Date: Feb 2009 Location: San Diego Posts: 39 Thanks: 1 Thanked 1 Time in 1 Post iTrader Rating: (0/0% )	My machine shop specialist tells me that the 20V ST or BT head are already high flowing so Port and Polishing doesn't do much of a difference unless you do supporting mods as well.