alright well i finally decided im gonna port my head and get a multi angle valve job.ive been told not to get it polished by some friends bc they say sometimes you come loose power from it.does anyone know anything about this?

and what power increases should i expect if i get my head ported with a multi angle valve job with a skunk2 intake mani?

thanks for your help ahead of time

and yes ive searched it didnt say much

 

They probably mean you can lose power if the port and polish is not done right.

 

porting and polishing increases volumetric efficiency.. more air flows in due to less restriction and greater flow. turbo guys usually get something called turbo swirl.. it makes better atomization of fuel and such... porting done badly increases restriction. dont mess up and watch your tolerances in the port walls and around the valves. i am in the process of porting and polishing my b18 head with a dremel.. works very well but lots of man hours.. good luck

 

bump

 

I wouldn't really touch the intake side, because those are made to have atomization effects. The exhaust side can have a mirror finish if you wanted because you only want the easiest flow out. The valve job has to be done correctly and not just with a dremel without knowing exactly how to do it.

GL

 

im not doing it myself im taking it to a shop
they said they would do everything for 700

 

The biggest issue is getting all of the ports to be as identical as possible. Some very well funded shops will hand port one of the ports and then have a CNC machine duplicate it on the other ports before hand finishing all of them. It takes a lot of time and patience to hand port all of the ports correctly.

I've had as much as 40 hours in a head before and that was a comparitively mild job compared to some.

 

^^cool, didn't know that. It makes sense though

 

but wouldnt it make more sense u get it done by a cnc machine so it will be identical

 

A smooth surface does not flow air as well as a dimpled one. I'm pretty sure it's the same reason golf ***** have dimples...

 

golf ***** have to displace air around them and need low drag due to laminar flow, while we are talking about air being put basically in tubes. Kinda the opposite effect actually so you DO want smooth surfaces for faster flow...dimples or roughness just create turbulence which is desired in a golf ball, but not for the exhaust side of an engine's head. Now the intake sid eis a different story because you want to promote atomization of the air/fuel mixture (hence valve swirls). I'm getting carried away here...haha

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">golf ***** have to displace air around them and need low drag due to laminar flow, while we are talking about air being put basically in tubes. Kinda the opposite effect actually so you DO want smooth surfaces for faster flow...dimples or roughness just create turbulence which is desired in a golf ball, but not for the exhaust side of an engine's head. Now the intake sid eis a different story because you want to promote atomization of the air/fuel mixture (hence valve swirls). I'm getting carried away here...haha </TD></TR></TABLE>

thank you! i wasn't sure

 

so basically i dont have to worry about it as long as its not a swag job and what power gains should i expect?

 

bump for the last time

 

B series heads can be very picky about port jobs. The most common problem for inexperienced porters is overporting the floor of the runners. This can hurt air velocity (and power) throughout the powerband. I typically take very little material from the floor and concentrate more on the walls. Make sure whoever ports it has some knowledge of fluid dynamics.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by adseguy &raquo;</TD></TR><TR><TD CLASS="quote">golf ***** have to displace air around them and need low drag due to laminar flow, while we are talking about air being put basically in tubes. Kinda the opposite effect actually so you DO want smooth surfaces for faster flow...dimples or roughness just create turbulence which is desired in a golf ball, but not for the exhaust side of an engine's head. Now the intake sid eis a different story because you want to promote atomization of the air/fuel mixture (hence valve swirls). I'm getting carried away here...haha </TD></TR></TABLE>

The turbulent boundary layer around a golf ball lowers the body drag force by keeping the boundary layer in contact with the surface and lowering the vacuum drag behind the ball. This applies only to outside flows with detaching boundary layers. You are correct in the fact that turbulence in general does increase drag for inner fluid flows.

Getting back to the original question, the caveat is that you need enough turbulence in the intake manifold (hence the GSR two-sage manifold) and cylinder head intake ports to properly mix the fuel with the air. If a cylinder head is severely ported, you can reduce this turbulence at low RPM and have poor mixing, which results in lower torque. Polishing the surface of the ports will lower the friction factor of the "pipe", and consequently the turbulence. The polishing will have a much lower impact on the turbulence than increasing the effective port diameter.

Those who are interested can play here:
http://www.fluidmech.net/jscalc/vmd03.htm

 

thanx a lot i found out what i need to know