NA builds. How far to go?

[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