iam porting a 12a, SP do i port the primarys and the secondaries or just the secondaries.. they look the same shape just the bowls and runners are bigger on the seconds.. thanks for your help

 

if you're going to bother with porting at all, do all the ports. you can do the primaries smaller if you're worried about idle quality, but don't just do the secondaries. not worth it in my opinion.

 

this will be street/track driven, so no worrys about the idle. thanks for your input tomorrow i shall port the rest iall put some pics up. my bowls and runners are almost mirror finish little more work and their there.
iam going with 12a street port intake & exh.
webber down draft.

wouldnt it make sense to mirror finish (polish) the webber's intake mani as well? whats the point of something being smooth if something in front of it's path is rough? even though the cast iron is much rougher than the intake manifolds path so maybe thats why..

 

you may want to reconsider the "mirror finish" idea. i know it's tempting, especially when you see some of the pics on these forums, but what those pics don't show is that the port surfaces retain some grit/roughness to them. get them smooth, but not glass/mirror-smooth.

reason being, you want some turbulence in the airflow to help with atomization.

 

i did not know this, thanks heres my exg.

 

Lets seen the other side??

 

well said !!

 

i forgot to mention that i was referring to the intake ports, specifically. for exhausts, i usually go as close to mirror as i am capable.

 

(some things still need to be cleaned) paint mark on the rear iron.. little buff mark on the rotor housing. but tell me what you guys think

 

You will not gain anything by getting the exhaust any smoother than the intake, we don't even polish them in our cup motors.