Double Pump vs. Standard.... Good? Why?

[pastortom1]

On a mildly warmed over 318, we have an Edelbrock Performer Intake and Carb setup, installed before we purchased the car.......the carb was without a proper choke, so we replaced the entire Carb with a new 1400 series Edelbrock Performer Carb (forget the actual number) and electronic choke.

The car just does not seem to really "get up and go" from a standing start............ I've drag raced 2 BBL Mopars in stock eliminator with better starts, to be honest.

I'm sure we could get better results if we took it in for a professional adjustment and dyno testing, BUT I've read lately that a good "double-pumper" would be MUCH better for this motor than the standard style Edelbrock we have, and especially for the rapid response I'd like to achieve off the line.

Could someone elaborate a bit on the differences between a double-pumper and a "non", and what benefits there would be...........and how about overall mileage when making such a swap...........what size CFM for a mild 318?

We appreciate the input.

 

[GoodysGotaCuda]

Just my 2cents. I run a 650 AVS, 3,500stall and 3.91s and theres no lack of getting out of the hole with my 318. Turned 1.9 60ft at 5,200ft which isnt too shabby...

Double Pumper vs 'Normal' as in 'Vacuum Secondary has the advantage, usually, for Manual cars or cars with high stall converters and low gears. Due to the fact it instantly runs secondaires and feeds the motor all four barrels based on how much throttle, and not just two barrels...then four barrels based on vacuum like a vac. secondary. This is good for manual cars and high stall autos because when dialed in right, you can usually get a better launch due to it being able to rev up (stall) or you rev it up (manual) before the load of the car hits the motor. A vac secondary will run 2barrels till the motor has a certain (tuned) velocity going through the carb to open whatever secondary type it is (holley the spring setup, eddie with the performer/afb or the avs). Just the motor idling will probably sound a little snappier with the double pumper....until to stick the load of the car on the engine and it just wont be able to handle that much fuel/air and will bog it out.

So unless you are running a manual or a wicked converter. In my opinion, the double pumper will hurt. Your AFB/Performer carb will be able to work best, actually a avs would be best, but the performer will work. Its just a much bigger pain in the *** to tune when the secondarys kick in (disassembly of the carb and grinding or adding weight to the carbs counter-weights), where as a AVS you need a screwdriver and Torx head to adjust the secondarys (WELL worth the money over the AFB/Performer)

Just my 2cents. I think the double pumper will hurt, probably a chevy guy told you that lol.

 

[rklein383]

The biggest problem I have had with double pumpers is getting the idle circuitry right. I think Holley set up double pumpers to idle very rich as they are basically a race type setup going on engines with very large cams and high compression.

If the engine idles well and doesn't load up, the other stuff is easy, in my opinion.

Rod

 

[dgc333]

There is very little difference in perfromance from a dialed in vacuum secondary vs mechanical secondary carb. On a "mildly warmed over" engine you are likely going to be much happier with the vacuum secondary carb. Plus it is going to take a lot more tuning to get the mechanical secondary carb dialed in.

 

[OldVart]

Get yourself a strip kit with an assortment of rods and jets, and dial that puppy in for YOUR engine. Once you get that Eddie set up properly, it will get out of the hole just like you want it to.

 

[moper]

Get yourself a strip kit with an assortment of rods and jets, and dial that puppy in for YOUR engine. Once you get that Eddie set up properly, it will get out of the hole just like you want it to.

What he said...

And also, very well put Goody...

 

[Jim Lusk]

Make sure the secondaries are even opening. There are other things that can cause it to be a dog off the line (incorrect convertor for the application, tall gears, etc.).

 

[C130 Chief]

Are you sure it's the carb? Cam/compression? Put your pump rod in the inner hole. Any change? Now try the outer hole. Unless this makes a really noticeable difference, the carb probably isn't the problem.