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Wich 600cfm DP carb? https://slantsix.org/forum/viewtopic.php?t=42659	Page 1 of 2

Author:	Polara1974 [ Mon Nov 22, 2010 6:04 pm ]
Post subject:	Wich 600cfm DP carb?
Hi all, I want to put a Holley Double Pumper on my new engine, although 600cfm might seem overkill at first I think that it will perform pretty good for a Hot Street-Strip Slant Six. I have read a lot of post about Double Pumper carbs here and couldn't found any post comparing carbs, asuming that a 600cfm is the rigth choice, wich do you think is the best option carb between this? Proform USD 415.- http://www.summitracing.com/parts/PRO-67211/ Quyick Fuel USD 378 http://www.summitracing.com/parts/QFT-HR-600/ Holley 0-4776C USD 340.- http://www.summitracing.com/parts/HLY-0-4776C/ Jet PErformance USD 602.- http://www.summitracing.com/parts/JET-4776S2/ About carbs differences the Holley is the regular one, withou any extra-tunning aids, like changeable air bleeds, floating sigth windows, changeable idle feed restrictions, also the Quickfuel and Proform are ligthweight aluminum carbs. The Jet Performance seems more race ready, but the difference in $$ is big ... Ok, I'm lost here, I do have a lot of experience with Holley 2300 carbs, but never played with 4bbl before, what do you suggest? Do you think that any of this is worht the money? Am I looking in the right direction? Regards, MArtin

Author:	Reed [ Mon Nov 22, 2010 6:12 pm ]
Post subject:
I would recommend a 500 CFM edelbrock performer carb.

Author:	DusterIdiot [ Mon Nov 22, 2010 6:14 pm ]
Post subject:	Uhhh...
I'd go with a 600 cfm vacc. secondary carb...that way the carb will only use the secondaries you need not everything at once like the DP... I currently use a similar carb that's been modded with annular boosters in all 4 holes for better atomization and response...it runs fine on the street but the mileage will limit it to the strip. You will have to rejet it and respring it to match your build. -D.Idiot

Author:	Polara1974 [ Mon Nov 22, 2010 6:44 pm ]
Post subject:
After a Holley 600cfm DP my second choice will be an Edy500cfm, it also seems to be more on the spot about advertised cfm (a Holley 500cfm DP woulb be the best match!!! in theory) But the thing with Edelbrock is that in my country the are no popular at all, so you can't find parts ... but for Holley there are a tons of parts!!! Not to mention that I understand Holleys pretty well. Now about VS vs. DP, the Quick fuel carb has the option to change the linkbetween the primaries and secondaries, so I can change the progression on those. The millage is not a problem, if the millage is poor, it's is OK too, as long as the I'm getting the most performance out of the engine, so I'm still thinking that a DP carb is the best option for performance use that a Vacuum secondaries, do you think so? Or should I start learning about Edelbrock carbs?

Author:	Joshie225 [ Mon Nov 22, 2010 6:53 pm ]
Post subject:
Unless you have a manual trans with steep rear end gears or an automatic with a high stall torque converter the car will almost always be quicker with a vacuum secondary carburetor. Never mind that a 600 is too much for all but the wildest of slant sixes. I wish Holley made a 390 Double Pumper that was calibrated for smaller engines and didn't cost $700+. I have one of those high dollar Holley carbs, but I bought it used. It's a # 0-80507-1 that has been reworked with undrilled throttle plates and smaller idle feed restrictions, but it still isn't calibrated right. A carb guru I trust said it's because the idle feed is on the wrong part of the metering block. One more thing that needs fixing.

Author:	72polara [ Mon Nov 22, 2010 6:54 pm ]
Post subject:
If you intend to get much street usage out of it, or if the car can even remotely be classified as "heavy", or has high gearing, or has an auto trans, I would pretty seriously consider the vacuum secondaries. DPs can be a pill to get right for 'normal' driving, not to mention the awful mileage and such. If you can do holley's, don't be too scared of the Carter style carbs; I just got a crash course in one after doing holleys/webers for years, and if you already have a basic understanding of carb operation/theory, they're actually pretty intuitive!

Author:	madmax/6 [ Mon Nov 22, 2010 9:39 pm ]
Post subject:
I tried a double pumper,couldnt get it to work nearly as well as my 600 vac holley.Guzzi Mark

Author:	Polara1974 [ Tue Nov 23, 2010 8:33 am ]
Post subject:
Ok, so maybe a little info on my car and engine will give you a clear picture. Th car is totally assembled, manual 4 speed (A240-4gears) with Dana44 on the rear with 3,73 gears. The engine will be 3780cc (stroke 100 / bore 3,50) large rod assy, fully balanced (ligthened crank and rotating assy), fully worked head (45mm intake - 40mm exhaust), with long headers, external oil pump, MP284 cam (later a custom gring about 300 duration), and CR around 9.5 - 9,7. I have three intake options, 1-4bbl (offy), 1-2bbl (stock) and 2x1bbl (stock alum.), so I figure that my besto option was to run the 4bbl. Now with this info maybe you can help me out a little bit more. As I said before I care about performance, not mileage, and the car will be 50% strip - 50% street (mainly goinga back and forth to the track!!) but should be able tu run on the streen and eventually handle traffic. Thanks, MArtin

Author:	Shaker223 [ Tue Nov 23, 2010 10:45 am ]
Post subject:
Mine works fine but a vacuum carb might be better.

Author:	Polara1974 [ Tue Nov 23, 2010 2:33 pm ]
Post subject:
Sorry to have so many questions about this ... but we do not have manu 4bbl in my country How about vacuum secondaries carbs with large overlap cams? How do they perform? Wouldn't be better a mechanical progresive 4bbl? Like this one that you can tune 1-1 or 60 or 40% primaries before secondaries. http://cgi.ebay.com/ebaymotors/QUICK-FU ... ccessories I though that my desicion was reduced to wich 600cfm DP carb to buy, but anyway!! LOL

Author:	slantzilla [ Tue Nov 23, 2010 3:47 pm ]
Post subject:
Try to find a vacuum secondary 390 Holley. IIRC the List # is 8007. Spend a couple more bucks and get the quick change secondary spring kit and you're good to go.

Author:	1974duster kev [ Tue Nov 23, 2010 4:18 pm ]
Post subject:
My holley 390 vac secondary works fine with a big rumpy cam Kev

Author:	Polara1974 [ Fri Mar 25, 2011 1:09 pm ]
Post subject:
I still can't decide on wich carb to choose .... 500 cfm Edys, QuickFuel 600cfm DP with interchangeable link for the secondaries or a 600cfm Vacuum sec. .... The thing is that I can't afford to make the wrong choice here, for me a USD 400.- carb ends up being a USD 800.- carb because of shipping and Customs taxes to Argentina ... so is a one shoot chance !!! About Double Pumpers: I still think that the Quick Fuel 600CFM carb Double pumper is the best choice with the possibility to change the secondaries open rating from 1-1 to 40% primaries before secondaries or 60% primaries before sec. ... How about making the opening progresive on the seccondaries? About Vacuum Secondaries: I'm having second thougths about Vacuum sec. carbs with cam overlap greater that 76Âº ... will they open at all? even with a ligth spring? About Edys 500cfm: This is my last resource, If i can't made up my mind about 600cfm VS versus DP i'l go this way ... but still I'll like to stick to Holley... I'm just speaking my mind here ... after reading almost ALL the post about 4 BBL here ... still can choose one carb for my car.

Author:	Joshie225 [ Fri Mar 25, 2011 1:29 pm ]
Post subject:
A 600 is too much especially with mechanical secondaries. The 500 Edelbrock is much better suited to a slant. I have a vacuum secondary Holley 390 and it works pretty well, but some people have trouble with them. I wish Holley made a 390 CFM double pumper that was calibrated for smaller engines and didn't cost $700 like the NASCAR HP model. I have one of the NASCAR 390s which has been reworked with solid throttle plates and smaller idle restrictions, but it's still not quite right and has no vacuum advance provisions.

Author:	emsvitil [ Fri Mar 25, 2011 2:12 pm ]
Post subject:
Older Mazda Rotary engines cam with small 4bbl carb. You might be able to find one of those locally.

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