i have an edelbrock carb on my 396. it is running way too rich and can't seem to adjust it. a friend say that edelbrock carbs are crap and not worth the price of a rebuild kit. he says i should put on a holley 750 double pumper. not a vacuum secondary(not sure what that is anyway). question is does anyone agree with this? any other sugestions?

i guess my choices are:
1. rebuild the edelbrock
2. get a holley 750 dbl pumper
3. get a holley 750 w/ vacuum secondary?
4. get an orig type rochester quadrajet
or
5.???

Thanks, Pat
'70 El Camino SS 396

a friend say that edelbrock carbs are crap and not worth the price of a rebuild kit. he says i should put on a holley 750 double pumper. not a vacuum secondary I'd say your friend doesn't know what he is talking about, and I would be leary of any advice he gives...

First, Edelbrock carbs are very good, but there are always lemons, and always people that don't know how to tune something different...

Secondly, the Holley Double Pumper is a good carb for racing, and can work okay on the street, but the Holley Vacuum Secondary is most likely a better choice for a street car than a Double Pumper(I am assuming thats what this is for, for the street).

These two facts tell me your buddy doesn't know what he is talking about...

Realistically, there will not be much difference in performance between either of the choices (this is for the street).

If your car can utilize all the extra fuel (sticky tires, good traction/suspension, high stall or clutch), then a Double Pumper will be a little better performance wise, but worse, mileage wise... But this usually isn't the case on the street.

I have run and tuned each of these many times, and with several cars have seen very little improvement in 1/4-mile ETs when switching... The best 1/4 miles on street tires have been with either Edelbrocks or Holley Vacuum secondaries (these were ALL street cars running DOT rubber and 12.90s-14.50 ETs). The DPs seem to "feel" better (seat-of the pants), but the performance numbers don't show it.

How much have you tried "tuning" the Edelbrock? Have you changed jets? metering rods? step-up springs? Pump linkage? Float level? Do you have a fuel filter? whats your fuel pressure?

Where is it running rich? Idle, cruise/part throttle or full throttle?

It might not need a full rebuild...

he says i should put on a holley 750 double pumper. not a vacuum secondary(not sure what that is anyway). All these carbs are 4-barrels, with two barrels being the primaries and 2-barrels being the secondaries. The secondaries are used when extra fuel/air is needed (and more than the primaries can flow.

The Double Pumper has Mechanical Secondaries, and all four barrels will be fully open when the gas pedal is pushed all the way down. This will happen whether the engine actually needs the extra fuel or not...

Your 396 or even a 540-inch engine will work fine with a tiny 2-barrel carb, but they will run out of fuel/airflow at higher RPMs. They generally don't need full airflow until spinning faster (especially a 396). The DP works great IF you can launch the car with the RPMs up where all the 750 cfm is needed, but otherwise doesn't do much good. It can be tuned to overcome bogs and such, but usually its usually just a crutch as its not really intended for lower RPM driveability...

The carburetor itself does not produce power, it only allows the engine to produce power by flowing the needed amount of fuel and air. Any of these carbs flowing 750 cfm will allow the same HP to be produced...

The Vacuum secondary carb has the secondaries throttles that are opened when the engine produces a vacuum signal "telling" the carb that more fuel is needed. It adds fuel/air AS NEEDED, and when properly adjusted, it works great.

So the Vacuum sendary adds fuels as the engine needs it, the Double Pumper adds it all at once, whether the engine needs it of not...

The Edelbrock is also a vacuum secondary type carb.

The Edelbrock design (originally Carter, but redesigned) has been around for many years (longer than the Holleys). Even the old Chrysler 426 Street Hemi used dual Carter carbs, so they are a performance carb.

All the Chevy Musclecars used Holley vacuum secondary carbs (even LS6s and L78 Chevelles). Not including crossram Z28s and maybe L88 Corvettes?). Why didn't GM use Double Pumpers on factory cars? Probably because the engineers realized they would be worse for performance for a street car...

Almost every street 396 works better with a Q-jet. They are an excellent design and can almost get decient gas milage with a BB.

Ditto to Tony. I like this fact filled response with little to no "opinions" (except maybe the part about the friend) :D

Definately go with a vacuum secondary carb, and if street driven, add an automatic choke.

Edelbrock, Holley, Q-Jet will all have their fans, you will need to choose yourself. I would definately rebuild the Edelbrock you have or have someone do it for you. This will likely be the least expensive way to go.

wow, that's alot of info tony. thanks for the details. well all i know is the idle adjustment screws don't seem to do diddly. the plugs were very black when i changed them and the exhaust has a very potent fuel smell. so im guessing its running too rich. i put on new cap/rotor/wires/plugs. could it be a timing thing? or?
i guess rebuilding the edelbrock seems like the best choice however, i wouldn't want to try rebuilding it myself. i have no experience. or is it easy? what size metering rods/jets?
or i could just pack it up and send it to you tony. interested? or can anyone recommend anyone near LA?
i don't care much about fuel economy i just want quick response and performance.

thanks, pat

Pat,

Maybe a vacuum leak? Maybe the fuel pressure is too high or dirt stuck in the needle-and-seat...

near LA??? I am in Nor Cal, but where are you? How close to Edelbrock are you? I think they are in Torrance and some other areas... Maybe see if they have any technicians that can help... Can't hurt to ask them...

Idle mixture screws only affect the idle... Is it running rich elsewhere?

I am assuming you don't have the Edelbrock manual for the carb? The manual comes with the carb, but maybe you can order or download the manual/chart for your model...

Definitely alot cheaper to tune or rebuild the Edelbrock you already have, rather than buying a Holley (and the new fuel line you will likley need...).

Rebuild if dirty or worn out, but maybe it just needs adjustment.

The Edelbrock is pretty easy to tune, but different from a Holley... Minor tuning is easier on the Edel, but mostly because the metering rods can be swapped in a few seconds (literally). With a Holley, you'd need to pull the fuel bowl (empty it first, disconnect the fuel line, likely replace the bowl and metering block gaskets and change the powervalve and jets to tune... easy but time consuming...

The Edelbrock manual (for each specific carb) has an easy to read chart with metering rod and jet combos to create rich &/or lean conditions at both part-throttle and full throttle conditions conditions... Some changes require only a metering rod change (I change these in about 30-seconds). Jets take a few more minutes to change, but still far easier than changing jets in the Holley.
Then there are the "step-up" springs that tailor when the system transitions from cruise to power. These springs are right under the metering rods, so again, very quick and easy to change/adjust/try different combos.

thanks again tony, i just went to the edelbrock site and was reading the manual..theres a section that reads:
When the manifold vacuum is low, indicating a high load such as a heavy part-throttle (or WOT) acceleration, the Step-Up Spring is able to force the Piston to the top of its bore and position the Metering Rod at the top of its travel. This action is called "Power Mode Staging". The portion of the rod now located in the jet has a smaller diameter, thus the restriction through the Jet is reduced and a rich A/F Ratio is provided for high load/high power operating conditions. This is the "Rich Step" of the Rod.
maybe my manifold pressure is too low? how do you check this and what would be an acceptable range?

thanks, pat
'70 el camino ss 396