Carb question

[stirling33]

What is the difference between a Holley double pumper 650 and say a Holley street avenger 670 carb?

If there is a difference what are the advantages/disadvantages of each?

Any input would be helpfull thinking of upgrading my carb.....

 

[69Rcode_Mach1]

The street avengers are basically a 4150 based carb. They have vacuum secondaries which makes them nice for a mild engine and can help with mileage. The double pumper has mechanical secondaries which will make you have better power if tuned properly but mileage will suffer.

 

[rbohm]

the double pumper carb is just that, you have accelerator pumps for each side of the carb, and both of them activate when you open the throttle, thus dumping a large amount of fuel into the intake tract. the avenger carb has vacuum secondaries that open only when the engine load is such that they are required to open, and have no accelerator pump on the secondary side.

 

[jcode68]

The timing of this thread is good for me as I am also looking into buying a new carb, although I don't mean to hijack your thread. Simple question (and opinions requested) what is the performance advantage of the double pumper over the vacuum secondary carb and is it worth any of the added tuning fuss?

 

[RATM]

ok, probably a stupid question, but how will i know just by looking at my carb if its vacuum or mech. secondaries???

thanks

 

[iskwezm]

ok, probably a stupid question, but how will i know just by looking at my carb if its vacuum or mech. secondaries???

thanks

there is a vac. can on the side of the carb,cant miss it.

 

[69Rcode_Mach1]

You could also push on the throttle with the car off and see if it dumps into all 4 venturis or just 2.

 

[D.Hearne]

Vacuum sec. Holley's have a vacuum canister ( pod) located on the opposite side of the carb from the side that the throttle linkage connects to. It's somewhat square on top, with 4 screws, the bottom side is funnel shaped and has a linkage rod sticking out the bottom that connects to the secondary throttle rod. Double pumper Holley's are mechanical secondary carbs only, the secondaries open up at about 1/2 to 2/3 into the primary side's opening, all 4 bbls are wide open at full throttle ( or should be)

 

[stirling33]

Thanks for the clarification between the 2 carbs, but is there any clear cut advantages one vs the other performance wise, and no I am not concerned about gas mileage, my car is not a daily driver.

 

[D.Hearne]

If you've got an intake with a big, open plenum, the double pumper will have a distinct advantage, as it can supply more fuel when you nail the gas pedal to avoid a lean condition.( but on the downside, if you choose one that's too big for the engine, it'll just kill it when you nail the gas) Now, vac. sec. Holleys can be modified to open the secondaries almost instantly on you'r nailing the pedal also and to provide almost as much fuel there too, which in some cases may provide an better off-idle holeshot than a double pumper. The vac. sec. carb is also more forgiving in tailoring it to the engine's needs than a mech. sec. carb. as you can play with different sec. springs to get the secondaries to open sooner or later.

 

[D.Hearne]

Thanks for the clarification between the 2 carbs, but is there any clear cut advantages one vs the other performance wise, and no I am not concerned about gas mileage, my car is not a daily driver.

Assuming your engine is a 302, based on what you've got listed Holley 600 Dp carb would be perfect, a 650? Maybe a tad large. But you can also get your 600 to perform almost as well.