CDaniel525

Ive been contemplating upgrading carbs recently...I have a Edelbrock 750 right now with vacuum secondaries, but a friend of mine was telling about how when i launch the car it looses its vacuum some and causes the secondaries to close, which makes sense cause i can sense what hes saying when im just cruising around on the streets cause if i dont let the clutch out slow or give it a lot of gas, itll bog down...

So i was thinking of going with mechanical secondary carb...As far as i can tell Edelbrock doesnt make a mech. secondary carb :bs . So what would be the best carb to go with?? If its a matter of gas mileage, i dont really car since its not my every day driver.If there is one with a electric choke i would rather get that, but if not id put one on after the fact.
Thanks....I appreciate your help...
Chris


[Modified by 74VETTE, 2:38 AM 11/24/2001]

PatsLs1vette

well chris you already know my view but lets see what everybody else says.

Jughead

I switched from Edelbrock to a Holley 3310 750 vac sec. This carb is a dual feed and not the double pumper. I was pleased with the ease of setup and outa the box plug and play traits of the Holley. It needs less tinkering than the Edelbrock which could never hold the idle speed?? I too question the value of the vac secondaries. Eventually I'm going to switch to a 750 double pumper with mechanical sec.

I don't remember exactly, but I think the Demon's were much more $$.

Larry B.

What is wrong with vacuum secondaries? If they are set right, they work great..... Especially on the steet. When you open the throttle, the vacuum does get lower but so does air velocity through the carb. This air velocity is what "pulls" fuel through the jets and delivery system of the carb. With a huge vacuum drop(like wide open throttle with mechanical secondaries) there is no air flow through the venturi's so performance is terrible (That is why a BIG one barrel won't work.). As the engine speed increases so does air/fuel flow through the carb. when the vacuum gets high enough to add more air fuel ( via the secondaries) they begin to open. This timing/rate is adjustable by the secondary diaphram on Holley's. On others they are adjusted by the air valve spring tension. So you have a "demand system" that will control the fuel/air flow as needed. When the secondaries open all at once, you will get a huge "bog" unless the engine is running fast enough to handle that much flow.On the strip you are revving the engine and pretty much keeping it wide open and mechanical secondaries work OK.

SteveG75

Why not a Q-Jet? Mine feeds my mildly modded L-48 (see sig) and still gets 18-20 mpg on the highway. It is actually a very sophisticated design.

Primary fuel flow is controlled by a power piston with a spring. Less vacuum more gas, like it should be. Secondarys are mechanical but with a large air valve door that only lets in as much air as the engine needs.

Paul 75 L82

Go with the Demon, I have the 650 Speed Demon and it's really kick A**.

79er

I vote for the Q-jet. You will not find a better carb for street!

je68

When I add my Demon with mec secondaries the diference was big. If set up right there is no bog. But you have to spend some time to get it right but when you do there are great.

Blkblt

Barry Grant Speed Demon.

No question.

Ask Lars. :yesnod: :yesnod:

**********
Jeff
Keep on :seeya :seeya :flag