MileHighDart
Well-Known Member
Title says it all
What makes a double pumper a double pumper?
- Thread starter MileHighDart
- Start date
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73Swinger18
✱ⓈⓌⒾⓃⒼⒺⓇ
Mechanical secondaries with its own accelerator pump.
mopowers
Well-Known Member
Two accelerator pumps. They have mechanically actuated secondaries instead of vacuum actuated secondaries as well.
MileHighDart
Well-Known Member
Thanks guys, I figured it was something like that, just couldn't figure out why they would have squirters for the secondarys.
How about these newer carbs like the Holley street avenger, or the Quick fuel SS680, both these are available in manual or vacuum secondary's , but are these double pumpers or do they just look like it because of the duel fuel line feeds? Considering one of these two for my 5.9 swap.
How about these newer carbs like the Holley street avenger, or the Quick fuel SS680, both these are available in manual or vacuum secondary's , but are these double pumpers or do they just look like it because of the duel fuel line feeds? Considering one of these two for my 5.9 swap.
Uhh...Two Pumps ??
Holley Street Avengers are available with vacuum secondaries only, and have 1 accelerator pump (primary side).
Straight from Holley's web site-
d55dave
Well-Known Member
Vacuum secondaries only open as the engine requires (when properly tuned) and therefore do not require an accelerator pump on the secondary side to help the engine overcome a stumble.
Double pump is generally a term that applies to holleys only. Vacuum secondaries only have one pump and can be identified by the vacuum pot on the side of the carb that opens the secondaries. Mechanical secondary holleys have no vacuum pot and, as stated earlier in this post. Have two accelorator pumps, thus "double pumper", one under each float bowl.
Double pump is generally a term that applies to holleys only. Vacuum secondaries only have one pump and can be identified by the vacuum pot on the side of the carb that opens the secondaries. Mechanical secondary holleys have no vacuum pot and, as stated earlier in this post. Have two accelorator pumps, thus "double pumper", one under each float bowl.
MileHighDart
Well-Known Member
All good info guys, thanks. Just trying to get all the choices sorted out in my head.
famous bob
mopar misfit
ARE YOU SHITTING US ?
MileHighDart
Well-Known Member
No Bob, I'm not shitting you.
We all have different backgrounds, and different levels of experience when it comes to hot rodding old cars. You're going to give me **** cause I didn't know what a doublepumper was, or cause I'm asking a question
Easy, Easy, Guys.....JK 
famous bob
mopar misfit
sorry about offending you, thot you might be kidding. just set and look at one , and think .Easy, Easy, Guys.....JK
yellow rose
Overnight Sensation
Hey! Don't knock watching cheese mold,....sometimes it moves!...............
The Street Avenger runs very well on all the projects I've dealt with using them BTW,....................
I tried to run a street avenger on the 340 in my Duster. Actually, Street Avengers, plural. A 670 and a 770. I have an A/F gauge on that car, and while I'm not a Holley carb tuning guru an A/F gauge makes things a lot easier. Now, the 340 in my Duster is making about 400 hp, has ported heads, doesn't make a ton of vacuum at idle, and it's a 4 speed car with 3.55 rear gears which are slightly higher than recommended for my cam, 3.91's preferred. It's a daily though and 3.91's don't cut it on the freeways around here. I swapped everything in those carbs more than a few times, I worked on those things for a long time trying all kinds of different combinations. Secondary springs, power valves, pump cams, pump nozzles, jets, the works. If the a/f was decent at cruise and part throttle there was a lean spot going from part throttle to WOT. Only way to get rid of it was to go rich at part throttle (bring the power valve in early, secondaries in early, giant pump shot, etc).
Long story short, I switched to a 750 double pumper. The mechanical secondaries and second accelerator pump solved the problem with very little tuning. Going to WOT looks like flushing a toilet it dumps so much fuel, but the A/F doesn't go rich and the plugs look good so the engine must want it. I did a bunch of searching, and found a few other cases of folks with stick cars and moderately (or hotter) built engines that had a similar issue with the Street Avengers vacuum secondaries.
Like I said, I'm no carb tuning guru, so maybe I missed something. And I still plan on using the 670 SA on my Dart (auto car, milder build), everything I've seen so far says that will work great. Just my experience with my Duster.
Long story short, I switched to a 750 double pumper. The mechanical secondaries and second accelerator pump solved the problem with very little tuning. Going to WOT looks like flushing a toilet it dumps so much fuel, but the A/F doesn't go rich and the plugs look good so the engine must want it. I did a bunch of searching, and found a few other cases of folks with stick cars and moderately (or hotter) built engines that had a similar issue with the Street Avengers vacuum secondaries.
Like I said, I'm no carb tuning guru, so maybe I missed something. And I still plan on using the 670 SA on my Dart (auto car, milder build), everything I've seen so far says that will work great. Just my experience with my Duster.
As fuel demand increases with performance, the need for more fuel arises. A vacuum secondary carburetor only has one accelerator pump and one squirter on the primary side. A really hot street or race engine will benefit from the immediate discharge of a second pump shot on the secondary side, just as the secondaries begin to open. Carburetors without an accelerator pump on the secondary side rely completely on the siphon effect to supply fuel to the secondary side. As the performance of the engine increases, that is often not enough, so another accelerator pump is added.
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