Gutting secondaries?

[FastFord]

Whats everyones opinions on this, I have been reading old threads all morning and have seen mixed thoughts on gutting the secondaries. I am pretty set on going ahead and gutting them as long as it is tuned in, but what does everyone else think about power lost or gained at different RPMs?

I would be running an NA Hybrid 3L with kinger PnP heads, extrude honed SVT UIM, and a big bore LIM.

 

[gomach1]

You know you want it!

 

[FastFord]

Hahaha^ That sure does look b e a uutiful!! Are those ports bored out at all? I was looking at the sho shop LIM, but its kind of costly, I will have to see how big the ports are on the heads. And how did you go about plugging the holes from the shaft?

 

[gomach1]

Just honed... I was gonna bore them but undecided right now. I welded them shut.

Sending more info in our emails....

 

[Blackcoog]

I wouldn't do it unless you were running forced induction. You are going to loose low end tq and won't gain enough up top to make up for it.

 

[FastFord]

I wouldn't do it unless you were running forced induction. You are going to loose low end tq and won't gain enough up top to make up for it.

Just curious what your theory is behind this. Wouldnt gutting them out and tuning for the additional air down low be very similar to an oval port 3L setup?

 

[Blackcoog]

The 3L gets low end tq in part from the design of the 3L upper and the 3L cams. Most don't post any more but people used to gut them and eventually switched back.

 

[mmc757]

The head design probably has something to do with it as well...
The 2.5 injectors are on one side while the 3.0 injectors are centered. They also have a different spray pattern.
A high air velocity is desired in the fuel/air mixing chamber to assure good mixing. In the 2.5 with gutted secondaries, poor mixing would occur at low RPM's due to the low air velocity and side-oriented injectors.
In the 3.0, the lower velocity was accounted for in the engineering by the injector design.

 

[FastFord]

Obviously Ford must have put the secondaries in to create more low end tq which is better for the normal driving conditions of a stock engine, therefore the injectors were better placed centered in the port that is used most.

Head design, if I am running PnP SVT heads with 3L valves on a 3L engine they are going to flow just as much or more than a full 3L engine at low rpm, therefore the one port is going to act as a bottleneck unless of course you bore it out to flow more air.

Hard decision here as there are many unknowns without a dyno comparison. Like how much tq would I even be losing at low rpm and gaining up top. If I didnt bore out the lower intake and just gutted the secondaries maybe that would be an equal balance here.

 

[mmc757]

Sell the SVT heads and go full 3.0. Nothing will flow more or better than that short of a custom UIM on the 3.0 LIM.

 

[FastFord]

Sell the SVT heads and go full 3.0. Nothing will flow more or better than that short of a custom UIM on the 3.0 LIM.

I would be all in with that as I have an oval port engine and this hybrid engine. Problem is I was told that the coolant passages on the block were welded shut to match up with the 2.5 heads. Not sure exactly what was done there.