Hot Rod Forum banner
1 - 6 of 6 Posts

·
84 Mutt
Joined
·
284 Posts
Discussion Starter · #1 ·
Stupid question here... :embarrass .If I were to put a secondary metering plate on my 3310vs 750cfm holley , would it be more of a double pumper?
If so, do I have to modify the sec.butterflies? Will it affect the vac.sec? I am going to pick up a holley book but , just wanted some imput from the pros. ;) :embarrass
 

·
Get in, sit down, hang on
Joined
·
2,785 Posts
Well, no.

Putting in a metering block (the wide one) would only give you the ability to re-jet the carb using standard screw-in jets .

"Double - Pumpers" are just that ... they have an accelerator pump on each float bowl, and have mechanical secondaries.

Two accelerator pumps are required in order to provide enough fuel to the engine during the transition phase (the time between when the throttle plates open and the venturies develop enough velocity to draw fuel through the main jets. There is also a power valve that supplies more fuel in between the accelerator pump and the main jets.)

Although "double-pumpers" DO have thier place -- on a manual transmission drag car for example, vacuum secondary carbs are a usually a better choice for automatic transmissions, and street-driven vehicles, and are also more economical.

Holley does make a selection of secondary springs which can be used to tailor the opening time and rate. Most carbs come "out-of-the-box" with a black spring ... which is the heaviest. My personal experience is that the purple spring (which is on the light side of middle) seems to work best on a ~350 cu in with an A/T, ~3.50 gearing in a mid-size car.
 

·
Get in, sit down, hang on
Joined
·
2,785 Posts
Slant3 said:
Thank you so very much! Duh! I forgot about the 2nd. acc. pump ! :embarrass Told ya it was a stupid question. :D I think I will crawl back in my hole now.
No need for embarrasment ... this "double-pumper" thing actually comes up a lot.

That's what this site is all about ... sharing of knowledge and experience, and learning from others. :thumbup:
 

·
Analog man in a digital world.
Joined
·
2,252 Posts
Slant3 said:
Thank you so very much! Duh! I forgot about the 2nd. acc. pump ! :embarrass Told ya it was a stupid question. :D I think I will crawl back in my hole now.
Don't feel bad, most people I know call any Holley with dual feed bowls a "double pumper" whether it is or not. ;)
 
1 - 6 of 6 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top