"Pinning" the secondaries open.

[Paul Workman]

Originally Posted by scottfab

I think that's it in a nut shell. I value being able to disable the secondaries per the original engineering design because I like the idea of removing temptation from my sons and others AND because I just don't seem to have as many issues with that system as others.
You're right about fewer failures with fewer parts. Still I choose to leave the wipers on the car even though that would be fewer parts to fail.
Each to his own and we owe it to newbies to see a clear picture of removing systems IMHO.

You're not alone - far as keeping the SPTs intact. None other than Marc Haibeck suggests keeping them in place, and has them in his car. (and I STILL haven't gotten a good answer from him as to why. So...There's that for fair and balanced.

But, the analogy of comparing the wipers to the SPTs is overly severe to exageration. Of course you'd keep the wipers!

With regard to the secondaries specifically (excluding wiper or ashtray analogies, etc), or to the point of keeping them or not, the topic is way over wrought, IMO. Keep 'em if ya want, chunk 'em if you don't. But, for me (and many others, including most of the FBI gang) it comes down to this (and others can decide)

1) Da bastards will never fail me (again), including actuators, check valves, tubing, rubber connectors, or the vacuum pump: secodary issues in general WHICH is one of the most commonly mentioned problems on this forum, e.g., "My secondaries don't appear to be working...

2) Performance?? The SPTs span the center of the air flow column, creating turbulance and theoretically (at least) some impedance to flow, i.e., HP loss. I have no "before and after" data to refer to, I admit. But, referring to laminar flow characteristics of air in a runner column, the highest velocity is in the center of the column. Mathematically, the impedance increases with the square of velocity. (Guess where the SPTs exisit??)

SO! in pursuit of best performance, I know them being gone is not impeding air flow and thus performance (tho I just can't quantify it at the moment, the principal remains valid - at least IMO).

3) In my case, and that of "a few" FBI motors, the stock SPT plates are now too small to seal the post porting column anyway, making the issue of keeping them or not rather moot.

4) CAREFREE drivability! Woo Hoo!

@ this point, I feel like to do or not to do SPT delete has run its course. One has (at this point) enough info to decide, one way or another, with the exception of one last point: As I pointed out before, the next phase for the LT5 eliminated SPTs all together, going to a single injector per cylinder. This was a substantial change from the previous design, and being a frustrated automotive engineer, I have to ask myself, "if the dual runner design was initially used for "some" reason, what changed the minds of the engineers to revert to a siamese runner and single injector?" (which is essentially what we have when SPTs are eliminated and BOTH injectors run continously, no?)

An engineering friend of mine used to say, "Simple and elegant always trumps complex and wonderful!"