Originally posted by Chris Hightower:
Ideally, a metal single-runner 3L upper would be best, with the 2.5L LIM matched and siamesed, and the heads tapered match on the ports.

That could take you over the 400WHP mark.

Just my opinion.


Not necessarily.

The split port manifolds have a much high cfm flow ability and a much larger port area. That is a given.

With forced induction the less restriction the more power from the exact same setup. Advantage split port manifolds.

Since Chris is already at or just over the compressor's rated limit and doing it with less boost pressure I'd say his setup in very efficient. (I calculated 110-112% efficiency vs norm)
Switching to smaller intake ports might get him to see higher boost pressure (it's just a resistance measurement) but definitely will produce lower overall cfm flow and therefore less power.


Now the ST220 did come with an Aluminum oval port manifold that is supposedly hand portable. (i.e. no bends and you can accurately open up each port identical to the other)
If have not seen one of them personally nor could fathom a price estimate.
It does sound like an intriguing part though...



Now the larger plenum volume of the oval UIM can show benefits over a stock split port manifold on a NA engine. (3L especially)
However most people seem to forget EHing the split port UIM adds volume as well as max cfm flow ability. The latter of which it already has an advantage in.

For instance I gained roughly 18-19% port volume over my DH UIM. That is at or "more likely" just slightly beyond the limit of the split port UIM though.

Funny thing is the 3L is 16.5-18.2% (vs 2544/2499) larger in displacement. Who knew...

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.