NTXOlds

Okay, let me start out saying that I have no intention of actually doing this, but after looking at the Holley website at the Sniper systems, I have to ask this:

If the Holley Sniper 2300 is rated at 580 CFM and is good for up to 350HP, would it be good enough for a good street build on a rebuilt Rocket 350 with the factory 2bbl intake? I assume that the "up to 350HP" is an ideal scenario with high flowing intake, heads, valves and exhaust, but 350HP is pretty reasonable for a street engine.

I see no reason not to upgrade to a 4bbl Edelbrock Performer or Performer RPM intake and a Sniper Quadrajet unit other than the additional cost, so on paper the 2bbl version actually looks pretty decent.

Thoughts?

joe_padavano

Since EFI is metering fuel based on measurements from sensors and a fuel map in memory, the number of "barrels" is irrelevant. Carbs use multiple smaller barrels to maximize the vacuum signal that meters fuel; EFI doesn't need this. A single throttle plate and "barrel" of sufficient flow rate is all you need. The aftermarket systems that have two or four "barrels" are designed more for compatibility with existing carb intake manifolds and for familiarity to "old school" hotrodders than for any performance reason. All that matters is that it flows enough air for the engine it's used on.

NTXOlds

Thank you, Joe! This is exactly why I posted this. If we assume that the factory 2bbl intake flows as well as the 4bbl intake, hypothetically there may be an insignificant difference in performance between the "2bbl" Sniper and the "4bbl" Sniper for street applications targeting 300-350HP. Interesting to consider.

Cutlass Fan

Isn't 580 CFM a little on the small size to support 300 plus hp?

oddball

For a carb, yes. For optimized air usage it's plenty. Carbs have to be over-rated because, like Joe said, a carb is relying on pressure signals which relies on air density and speed. It's unlikely a carb every actually flows its rated CFM.

joe_padavano

^^^THIS. Keep in mind that carbs are rated at a steady state pressure drop (and that pressure drop is different for 2bbl and 4bbl carbs). The reality is that engine airflow (and thus carb pressure drop) is a very dynamic environment, and steady state measurements are only one data point. And also keep in mind that not every application needs to be designed for maximum WOT performance. Low speed and part throttle driveability may be more important than max HP for a given application.

NTXOlds

Joe, would you say that an Edelbrock Performer 2711 / 3711 would flow better than the factory 2bbl intake? If so, would you suggest that the Holley Sniper Quadrajet replacement with the spreadbore configuration would offer superior low speed and part throttle driveability than either the "2bbl" Sniper or the square bore Sniper due to the smaller primary throttle bodies?

joe_padavano

Yes

Go back and read post #2. The size of the throttle bores means nothing for EFI. There are no venturies in an EFI throttle body, so there is no difference in responsiveness with one, two, four square, or four spread if the total airflow capability is the same. Obviously the 2bbl version doesn't have the same airflow capability, but a 2bbl or even 1bbl throttle body with the same airflow would have the same performance.

NTXOlds

Thank you, sir! Sorry. I forgot that you addressed this.

Cutlass Fan

Thanks Joe and Oddball, you have explained it well.