vacuum secondaries -vs- mechanical... throttle response

Discussion in 'Classic Mustang Specific Tech' started by BelueLX, Jun 1, 2004.

  1. Ive heard to get a carb with mechanical secondaries for throttle response / drag racing. I found a good deal on one with vacuum secondaries. How much will the vacuum secondaries hurt me off the line and at the strip? Havent really dealt with carbs much Ive always had efi. Thanks,

    Cody B
  2. I am running a Quick Fuel 850 w/ vac sec and I have a 1.70 60' time. A friend of mine is running a 750 double pumper and has about the same 60' time. Its funny that the guys running carbs are looking into EFI and the EFI guys are looking at carbs.
  3. best 60' with the charger was a 1.74. im going to try the vac carb if i dont like it i can always sell it for what i paid.
  4. My Classic Mustang will stay carbed until the world runs out of oil.

    But any new car I ever buy would stay EFI.
  5. vacuum vs mechanical secondaries have been debated since forever it seems. depending on your combination i doubt you will lose much if at all, and the difference in driveability between the two can be great on the street, again depending on your combo.
  6. What I've heard is that mechanical secondaries are better for manual transmission cars, vacuum for automatics. But, that is for the street, I think.

    If you go to Holley's web site, you can email them and get the experts' opinion.
  7. another question: with a C4 transmission and a 3.73 gear, how many miles per gallon is normal?
  8. Cant you make a vaccuum secondary carburetor perform as if it has mechanical secondaries simply by modifying the throttle linkages on the carb?
  9. You can, but that presents a problem. You don't have the extra squirt of fuel that a second accelerator pump provides, which would mean you would bog out pretty bad.
  10. Exactly. You would have just built an expensive Edelbog. :rolleyes:
  11. grrrr, wish my speed demon was mech secondaries