NA builds. How far to go?

[oldeskewltoy]

The definitive word...... there isn't one!

When it comes to discussing the 16V 4AGE and the 2 different heads... most people make assumptions. When you do a little bit of research you'll find there isn't a huge difference... especially when an aftermarket intake system is utilized.


As to porting each, I can speak from experience that you almost never touch "open" the largeport ports, what you can do is to carefully adjust sections of the port to aid in getting the intake charge to turn toward the valves. While on a smallport there is a lot more work inside the port, especially if you plan on oversize valves.

By the way, "ports", are different from "bowls" and "seats". The "port" is the section where it enters the head, to where the splitter begins. The bowls, are from the splitter down to the valve seat, and the "seat", is where the valve seals (when closed) the combustion chamber

[jondee86]

(08-27-2018 07:37 PM)oldeskewltoy Wrote:  When it comes to discussing the 16V 4AGE and the 2 different heads...
most people make assumptions. When you do a little bit of research
you'll find there isn't a huge difference... especially when an aftermarket
intake system is utilized.

Yussss... most of the difference is in the intake manifold design. The
TVIS engine needed to close off half of each port at low rpm to keep port
velocity up to aid low rpm operation and gain a bit of bottom end torque.
But the smallport engine had a redesigned intake with smaller intake runners
that gave improved port velocity without the need for the TVIS system.

When using a single throttle intake it is common for people to "cut-n-shut"
the smallport manifold and fit it to the bigport head with an adapter plate
to obtain a performance improvement. However, as said, once the single
throttle manifold is discarded in fovour of ITB's, the difference between
the two heads is less evident.

Port velocity is the key to low rpm performance, but there is a point at
which port size becomes a restriction. Hence the belief that the bigport
head is better for high rpm/high power applications. Either head will flow
enough air for your power goals with the correct porting technique.

Cheers... jondee86

[kazi]

well ive emailed a few different places and waiting to see what they say.

[squeak]

160 at flywheel is easy, 160 at wheels is expensive !!!!!!

[kazi]

got a few responses back and long story short is small port 7 rib is the way to go on ITBs. just so happened that 2 fell into my lap last night so watch out on my thread. it'll take time and will be doing as much as i can myself.