Heyall,

I'm just thinking here, and throwing out ideas as I want to get to the 400hp level NA, but probably the only way is TPI, not TBI (or all carb, but not doin that).

Idea:

Call me stupid but could this work.

Take a standard Holley carb VS with the stiffest springs on the secondaries (to allow them not to open until damn near WOT). Modify the primaries (plug ports whatever you have to do) and mount the injectors above the throttle plates.

This may be the stupidest thing and I could get called an idiot here, but I don't care. Ideas are exactly that; Ideas.

Then you would have basically a TBI at normal operating conditions, but when you hit WOT the secondaries open up and the rest is history. Could this possibly work...

*** Imagine a QJet modified and you all know what happens when those big @ss secondaries open up!! ***

Maybe even a solenoid mounted to completely block the secondaries for just normal driving. heh

I'd go just carb, but if you could have the drivability and efficiency of FI, with the raw power of carb available if you need it, sounds good too me. And would save a PITA switching to TPI...

/Idea

 

Half computer + half carb = Q-jet

Your idea is novel but far fetched. It would be easier to just run a properly tuned carb. All of that un-metered air would cause tuning problems for TBI.

 

That at the crank or at the wheels?

That aint gonna happen with TPI either, not without serious mods and $$$

 

Agreed with Shifty. What you describe sound like a wiring/tuning nightmare. If it were my car, I would just go all or nothing, carb or EFI, not some crazy mix.

 

Heh, yea does sound kind of crazy.

As for the 400hp NA. The shortblock is a 383 and if I go TPI (will be a stealthram based build). 400 flywheel fyi.

I'm really getting interested in the 6.0L (408) Gen III builds but thats some big $$$. With a wife and child not gonna happen anytime soon unless I hit that lottery ticket number.

I was just throwing something out to see if anyone has tried this b4. W/ the tbi systems out there I am going to have a hard time w/ my 383 unless I go w/ a holley 4bbl setup, but If i'm goign to spend that kind of money I will go multiport.

I might just be forced to put a carb on until I can afford a TPI setup - but would really like to utilize the TBI since well, its already there...

 

By TPI do you mean an aftermarket piece like the Steath Ram? Or are you planning a aftermarket base and runners, but still keeping the long tube runner design? I think a stealth ream or similar system on top of a 383 with a good set of heads would be good for at least 400 crank hp. Its a very modest goal you are after, and a 383 would make it fairly easy. Try a search for the various multy point systems and you can get an idea for the kind of power that they are capable of turning out, if you haven't already done so.

If TBI is what you want, Holley offers 4v Commander 950 systems, both TBI and MPFI. If TBI is what you would get, for a 383, I would get their 900cfm version. For the MPFI, it would depend on what you plan on doing.

I personally have always wanted to swap to a Holley MPFI.

 

If money is the problem and you are serious about making that kind of power without experimenting/pushing limits of the 2bbl tbi, then you really cant go wrong with a Holley 4bbl tbi setup for the price. $1,400 gets you the tbi, sensors, harness, ecu, fuel pump, and true tuning ability. Swapping to a tuned port setup that will support that kinda power will cost quite a bit more, as will swapping to multiport

 

The stealthram isnt a TPI. TPI has long "tuned" runners, which kills HP above 4500 rpm, but has good midrange/low torque.
The stealth ram has very short runners and makes power past 6000 rpm, but low end torque suffers a bit.
I dont know if ive ever heard of a NA tpi making 400 hp at the rear wheels.

 

1984 LG4.
CCC system

They **can** be made to run really well.
Be prepared for alot of work.

With a real mild 355, and using a Cross Fire base I was running 13.6 with a CCC.

It all gets to a point of how much effort do you want to put into making a point. 400 HP on TBI?. The SS454 truck guys do that all the time, from what I've read.