thinking of swapping to dual quads??

[Grumpy]

Grumpy, I just got back from a local car show where a guy had a 1969 big block camaro with a low rise dual quad edelbrock intake installed, on what he claimed was a 11:1 compression 540cubic inch big block engine, not only did that car have a very impressive sounding engine, it also effortly smoked a set of very large pair of impresively wide tires with almost zero effort,
(the engine rpms were just not that high from the exhaust note)
and without running the rpms up, very high, the car just seemed to come alive as the throttle was depressed, the whole car seemed to raise up a bit as the tires effortlessly spun.
now I have always liked that nostalgic look of in line dual quad carbs , but now I just flat out want the look even if I can,t afford to build the same engine!

Your not the only guy that likes the look and sound that a properly set up dual quad induction provides on an engine that properly set up with the type of cam that takes full advantage of the induction systems designed in strong points, and love the sound of the three seperate stages in a progressive dual quad set up as each stage opens to an increasingly louder roar, now obviously doing a bit of research before throwing money into the engine build will help, but theres really no reason you can,t run dual quads on the street. while I swapped to crower fuel injection, during most of the time I owned a 1969 camaro, I did run dual quads on it for several months

heres a picture the wife took of me next to my camaro back 43 years ago

heres a nice looking 1969 camaro

ID certainly point out that a common 4 barrel carbs rated flow is meassured on a standard industry vacuum reading of 1.5" or mercury , and a change in vacuum changes the effective air flow!
think about that....
that single 600 cfm rated carburetor , you were using ,might see 17 inches of plenum vacume on a rpm air gap single carb intake!
put the same carb, on the same engine, with an identical second carb, bolted on a dual quad manifold, and youve effectively doubled the venturie surface area, effectively reducing the plenum vacuum at W.O.T. so theres no question that the carbs will need to be re-tuned from the way they were set-up to function correctly

http://wallaceracing.com/intakecfm.php

http://www.wallaceracing.com/runnertorquecalc.php

http://garage.grumpysperformance.com/index.php?threads/dual-quads.444/

http://garage.grumpysperformance.com/index.php?threads/tuning-a-tunnel-ram-intake.5175/

http://garage.grumpysperformance.com/index.php?threads/options-on-dual-quads.11047/

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/options-on-dual-quads.11047/

http://garage.grumpysperformance.com/index.php?threads/cooler-denser-air.8961/

http://garage.grumpysperformance.co...-the-holley-4150-and-4160-series-carbs.10736/

http://garage.grumpysperformance.com/index.php?threads/custom-throttle-linkage.861/#post-36523

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

the sub links should be read also
with some thought and fabrication skill a dual quad EFI tunnel ram is easily set up with twin 4 barrel throttle bodys

keep in mind that the newer self learning computer software available,
potentially makes the twin throttle body EFI on the cross ram, in line or tunnelram intake a far more,
realistic and much easier to tune induction system, now than it was in the 1960s-90s


http://www.efisystempro.com/efi-pro-hangout/building-twin-4bbl-throttle-body-engine

http://fitechefi.com/products/30061/

http://www.superchevy.com/how-to/en...-into-the-latest-efi-systems-on-market-today/

http://www.hotrod.com/articles/car-crafts-giant-efi-test/

http://www.hotrod.com/articles/self-tuning-efi-systems/

http://www.enginelabs.com/news/entry-level-self-tuning-efi-showdown/

http://www.youngsperformance.com/

http://www.bgsoflex.com/megasquirt.html

http://members.ozemail.com.au/~davodos/Megasquirt.html

http://www.glensgarage.com/catalog/index.php

http://megatunix.sourceforge.net/

the MegaSquirt Forums http://www.msefi.com/

ok assuming youll start with the rather common 600 cfm holley carbs

Id start with 5-to 5.5 psi psi of fuel pressure at the carb inlet
(BE DARN SURE TO CORRECTLY SET THE FLOAT LEVELS ONCE THE ENGINES UP TO OPERATIONAL TEMPS AND ADJUST THE VALVES)
(YES YOU NEED A FUEL PRESSURE REGULATOR, GUESSING AT THE FUEL PRESSURE NEVER WORKS AND JUST BECAUSE ITS 5 PSI AT 1000RPM IS NO GUARANTEE ITS STILL 5 PSI AT 6000 rpm,
UNLESS ITS VERIFIED AND CONTROLLED WITH A FUEL PRESSURE REGULATOR AND A PROPERLY MATCHED FUEL SUPPLY SYSTEM)
a fuel pump rated at 120-135 GPH at 7-12 PSI and a HIGH QUALITY RETURN STYLE FUEL PRESSURE REGULATOR FUEL SYSTEM WITH 1/2" ID lines can prevent most fuel supply issues

Id start with 6.5 power valve
http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/

and 68 jets all around

and plain or brown secondary spring
http://garage.grumpysperformance.com/index.php?threads/holley-carb-secondary-springs.8126/


blue accelerator pump cam
http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/

LEARN TO READ PLUGS
VERIFY THE ALTERNATOR VOLTAGE OUTPUT
(use of a 200 amp alternator and multiple good electrical grounds can prevent many mysterious intermittent ignition issues)
DON,T IGNORE OR SKIP READING LINKS AND SUB LINKS
VERIFY EXHAUST BACK PRESSURE
VERIFY IGNITION WIRE RESISTANCE OHMS
VERIFY TIMING CURVE
GET AN INFRARED THERMOMETER FOR TUNING
Ive found its a whole lot faster to use a quality IR temp gun, to locate a individual cylinder that's mis-firing as it tends to run significantly cooler than adjacent cylinders, or hotter if its a vacuum leak at times, as lean F/A mixes tend to run hotter
(Ive used this one for years)

http://www.professionalequipment.com/ex ... ermometer/
Wide temperature range from -58 to 1832°F (-50 to 1000°C)

http://garage.grumpysperformance.com/index.php?threads/spark-plug-info.202/

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/

http://garage.grumpysperformance.com/index.php?threads/reading-plugs.5428/

http://garage.grumpysperformance.co...conductive-grease-for-ignition-modules.10748/

http://garage.grumpysperformance.com/index.php?threads/why-use-anti-seize-paste.9424/

http://garage.grumpysperformance.co...ition-wires-getting-the-header-clearance.840/

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/