vacuum secondary vs. double pumper?

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magnumdust

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I think i'm gonna spring for a new carb at the end of the week and i dont know if i should go with a vac. secondary or a double pumper?

This for a 360 duster, 904 tranny, 3000 stall converter, street/strip car.

I'm currently running an edelcrap 1406(600cfm) and the vac. secondaries seem to work ok, but is there any justifiable performance edge to the DP?
 
You might could run either. What gear do you have?
 
How much street and how much strip?

A correctly set up vacuum secondary carb should preform as well as a puddle dumper, problem is, most people don't take the time to set one up correctly.

Generally, if a car sees mostly street time (75% plus or so), I prefer a VS.
 
ive always thought it's best to use a mechanical secondary carb for a manual trans. car...??
 
back to back test on my 69 barracuda....the 750 dp is a good tenth qucker then the 750 vacuum secondary ....both carbs have billet bases..proform main bodies...billet metering blocks...and the vacuum secondary carb uses a quick fuel adjustable pod ...

leaving on a trannybrake with throttle on the floor and two step at 3000 rpm...
 
mopardude318 said:
ive always thought it's best to use a mechanical secondary carb for a manual trans. car...??
Click to expand...

As a generalization maybe, but throw a 750/850DP on a heavy 4 spd. with low 3 gears and that's not gonna work well either. Weight, gearing and converter if Auto. is usually the deciding factor.
 
mopardude318 said:
ive always thought it's best to use a mechanical secondary carb for a manual trans. car...??
Click to expand...

Yes, it is. But if you have a loose enough converter and enough gear, a DP can be quicker.
 
70aarcuda said:
back to back test on my 69 barracuda....the 750 dp is a good tenth qucker then the 750 vacuum secondary ....both carbs have billet bases..proform main bodies...billet metering blocks...and the vacuum secondary carb uses a quick fuel adjustable pod ...

leaving on a trannybrake with throttle on the floor and two step at 3000 rpm...
Click to expand...

X2 except no trans brake both stock Holleys but the VS had a lot of track time with various springs and was well sorted. My car picked up 2 mph and .2 in the quarter.
 
With the Automatic, I would go vacuum secondary.
Double pumper for a 4spd.
 
next test n tune....took 73 duster 360 with 750 vacuum secondary carb...14.31 @97 mph....replaced with a stock 750 dp except for jetting for vegas....car ran 14.011 @ 101.26

converter flashes to 2200 ...3.23 gears...225/60/14 tires...stock suspension...
 
I run a 650 DP on my 340 and the engine loves it, works great! I have an M1 intake with a 1" super sucker aluminum carb spacer, 4-speed trans with 4.11 gears

:burnout::burnout::burnout::burnout:
 
I know the OP was talking about a street/strip car,..............But walk thru the pits at any dragstrip and count how many 4spd's, then count how many Double Pumper's.:D


Just to clarify, what i was getting at was out of 100 cars you'd find 90 DP's and probably only 5 4spd's.
 
1968FormulaS340 said:
How much street and how much strip?

A correctly set up vacuum secondary carb should preform as well as a puddle dumper, problem is, most people don't take the time to set one up correctly.

Generally, if a car sees mostly street time (75% plus or so), I prefer a VS.
Click to expand...

Hmm I guess 50-75 street/50-25 strip as I usually drive the car every weekend and go racing 1-2 times a month
 
magnumdust said:
Hmm I guess 50-75 street/50-25 strip as I usually drive the car every weekend and go racing 1-2 times a month
Click to expand...

Not sure how stout your engine is or what intake your running but i like the 670/770 vac. Holley street avengers. Could go with the regulation 4160 mdl. 750 vac. but it has a secondary metering plate instead of block which i personally don't care for.
 
magnumdust said:
I think i'm gonna spring for a new carb at the end of the week and i dont know if i should go with a vac. secondary or a double pumper?

This for a 360 duster, 904 tranny, 3000 stall converter, street/strip car.

I'm currently running an edelcrap 1406(600cfm) and the vac. secondaries seem to work ok, but is there any justifiable performance edge to the DP?
Click to expand...


With a 3000 stall I'd be all over a double pumper. also assuming deeper gears than or 3.00 or better with a 25 inch tire or less which would effectively be about a 3.40 ratio, 3.23 would be about 3.63 and so on...
 
If it was me I would get a double-pumper and use it for the strip or running hard on the street, then swap the Edelcrap back on when I wanna go cruising to get good gas mileage.
 
A double pumpers fuel mileage is directly related to the pressure a right foot applies.

I've had cars with 750 DP's get 20+ mpg in the highway and 16 around town.
 
MOPEkidD-3 said:
If it was me I would get a double-pumper and use it for the strip or running hard on the street, then swap the Edelcrap back on when I wanna go cruising to get good gas mileage.
Click to expand...


Edelcrack or Thermoslob, the TQ giving crisp throttle response and MILEAGE
 
MOPEkidD-3 said:
If it was me I would get a double-pumper and use it for the strip or running hard on the street, then swap the Edelcrap back on when I wanna go cruising to get good gas mileage.
Click to expand...

Honestly, the edelcrap gets bad mileage now. I cant imagine it being worth the effort to swap carb's.

Plus i'm kinda done with this one. After i rebuilt it, it ran way too lean. Bought a calibration kit, still too lean, and now i really don't wanna put more money into a carb that's too small for my application.

As for the carb selection, I'm likely going for that summit carb(the rebranded holley that was originally a rebranded motorcraft). Its got some great reviews online. The other possibility is if the shop i'm going to tomorrow has a holley to sell me(the guy has wall to wall carbs hanging in the shop)
 
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