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Double pumper vs vacuum secondary

Posted By: chargers777

Double pumper vs vacuum secondary - 06/05/09 03:56 AM

What are the pros and cons?I have never had a double pumper.I have always had vacuum secondary.The car is a 73 roadrunner 440 which is stock.Looking at some spreadbore double pumpers.How would they work on this car?It has 3.23s and is street driven.Most I have found are 650s would that be enough or do I need an 800?Opinions please.Thanks.

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Posted By: Dusted_Ya

Re: Double pumper vs vacuum secondary - 06/05/09 04:06 AM

What do you have now? I think vacuum secondaries are more accurate at metering fuel.
Posted By: DaytonaTurbo

Re: Double pumper vs vacuum secondary - 06/05/09 04:34 AM

You definitely do NOT want a double pumper for your application. Heavy car + stock 440 + 3.23's + auto trans(I assume) = bad. A double pumper is not for you, stick to a vacuum secondary carb. If you want a spread bore carb, do what I do and run a thermoquad. It runs great on my 440 in my satellite plus gets good fuel mileage for what it is.
Posted By: chargers777

Re: Double pumper vs vacuum secondary - 06/05/09 05:17 AM

I have the 73 850 cfm thermo quad that came on it and it ran ok.Thermo quads just seem problematic to me and holley are easy to work on and find parts for.
Posted By: chargers777

Re: Double pumper vs vacuum secondary - 06/05/09 05:19 AM

I have a 600 cfm holley on it now.Which seems to small.
Posted By: landon1

Re: Double pumper vs vacuum secondary - 06/05/09 11:13 AM

my 71 is 440/auto/highway gears...and i love my DP - they say they're not good for heavy automatic cars, but i'm sure lots of people have been putting them on since they came out. I had nothing but problems with VS Holley carbs, and i think the DP is the best carb (i've heard GREAT things about TQs from a local guy, but never tried one)
Posted By: Crizila

Re: Double pumper vs vacuum secondary - 06/05/09 12:27 PM

Quote:

You definitely do NOT want a double pumper for your application. Heavy car + stock 440 + 3.23's + auto trans(I assume) = bad. A double pumper is not for you, stick to a vacuum secondary carb. If you want a spread bore carb, do what I do and run a thermoquad. It runs great on my 440 in my satellite plus gets good fuel mileage for what it is.

Got my vote!
Posted By: JimG

Re: Double pumper vs vacuum secondary - 06/05/09 03:04 PM

Quote:

Quote:

You definitely do NOT want a double pumper for your application. Heavy car + stock 440 + 3.23's + auto trans(I assume) = bad. A double pumper is not for you, stick to a vacuum secondary carb. If you want a spread bore carb, do what I do and run a thermoquad. It runs great on my 440 in my satellite plus gets good fuel mileage for what it is.

Got my vote!



I learned this lesson at young age. I had a '78 440 Fury cop car. Heavy car, tight converter, low (numerically) rear end gears. Long story short, I put an 800 double pumper on it. What a dog! You had to feather-foot the throttle until the RPM came up, or it was very evident that the car was slowing down as the throttle was increased. You had to learn how to drive the car and always be aware of throttle position, and gradually increase the throttle as the revs came up. After I got tired of that nonsense, I ran a non-lean burn Thermoquad on the same car and it ran great. It didn't look all racy and cool like the double pumper, but you could smack the throttle to the floor any time and the carb did the rest.

I've also run Holley 3310s (750 Vac sec) on mild 440s with great results after tweaking. So have a zillion other folks.

My advice - don't make the same expensive mistake I made when I was young and foolish. TQ or Holley VS would be my recommendation.

Jim
Posted By: DaytonaTurbo

Re: Double pumper vs vacuum secondary - 06/05/09 05:19 PM

Quote:

I have the 73 850 cfm thermo quad that came on it and it ran ok.Thermo quads just seem problematic to me and holley are easy to work on and find parts for.



TQ's are harder to get parts for, but everything is out there. I've been using my thermoquad in my 440 as my daily driver for 6 years and it will light the tires on demand. But I did invest some time tuning the choke and the secondaries.

If a DP's what you want, send me a pm, I've got a 650cfm holley spreadbore DP with a complete holley jet kit I would sell. 650dp is probably the best size for a combo like yours.
Posted By: BSB67

Re: Double pumper vs vacuum secondary - 06/05/09 11:14 PM

I've used what you are describing: 800 DP spreadbore Holley, fresh stock rebuit 440, heavy car, 3.23 and an auto with 12" stock converter. The car ran great. Fried the tires at will at any speed in 1st gear. That was 20 years ago and I still have the carb mounted on the intake with fuel line and air cleaner sitting in storage ready to go. I've loaned it out to others as-is and they all had very good results as well.

This was with a stock cam, factory spreadbore intake, and exhaust manifolds, but the engine was fresh and an honest 10:1 CR. We did run it on a low comp. stock-like 440 GTX and it ran very well too.
Posted By: 68Bullit

Re: Double pumper vs vacuum secondary - 06/05/09 11:29 PM

I am currently using a 750DP on my heavy small block Charger with 904. It is tuned extremely well. I do have a MP 2600 convertor and 4.30SG gears but otherwise a very mild and heavy car.

I do not rank it above my TQ, but I don't rank it any less either. Just a little less in the way of fuel mileage maybe
Posted By: 69L78Nova

Re: Double pumper vs vacuum secondary - 06/06/09 02:52 AM

Run a TQ. I wont run ANYTHING else on a street car
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