Hey guys,



My setup is a 12a with a weber 48 with 39mm venturies IDA carb. I bought RB street port templates, and a full rebuild kit. Now just to make sure i have everything correct, as i've read a bunch of different theories on porting. this car will be street driven, and i need it drivable with plenty mid range power. As my understanding goes, when porting my setup i should port the rb shape into the irons and the basically just round out the inside making a smooth transition with a constant radius, is it true that i should leave the size of the port runners alone? also i've read post in favour and against exhaust porting, is exhaust porting recommended for my setup, i was thinking if i were to port the exhaust i would just bring down the bottom opening to match the sleeve. exhuast noise is not really a concern for me.



Thanks for clearing things up, Matt

dont the rb templates come with exhaust port template?



if this is for an NA you want to port your exhaust up around 2-3mm from stock and down about 3-4mm. dont go out side to side too much just match the exhaust sleeve.

you want overlap on an NA, since you can tune yoru header and intake to take advantage of it and make more power. porting the exhaust as is above will not affect much of any part of the cars drivability, except that it will become more responsive and make more power.

on the intake go up about 3-4mm and dont go out to the side more then about 2mm and that will keep your overlap on both the intake and exhaust to a point where drivability wont be of a concern, go more then this and idle will start to suffer as well as low end drivability of the car. also without some extensive modifications huge ports will not just make power on their own.



good luck

When porting should i port the roof of the runner, only where the outside edge is to smooth it out a bit?