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  #1  
Old 02-22-2000, 02:15 AM
DAVE JONES DAVE JONES is offline
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I posted a question on 2/19 that I havent had one response on yet. it was regarding some six pack questions that I had. You guys are the pros and I really look forward to your input. Some time ago a did ask a few questions regarding 6 packs in general and you gave me some great input. Now that I have one I would really appreciate your input again. Thanks......DAVE

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  #2  
Old 02-22-2000, 03:33 AM
J-BODY J-BODY is offline
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This is far from a pro answer, but this is my limited experience. Ran a 6 pak on a 340 in a 80 Mirada with 3.23 gear. It was basically stock with a .484 MP cam, 2800 converter. Car was a dog out of the hole, but it's main intention was good highway cruising, and it did that very well. Started changing to street racing and went to 4 bbl. Was running a .557 mech cam, and we decided that we would try the 6 pak. Actually went 60 ft. good, but with big cam lost vac signal and the end carbs wouldn't stay open. So if you go big on the cam you will probably end up playing with the springs in the secondaries (outboard carbs). Like the books say just look at the 6 pak as a 4 bbl with a extra set of secondaries.
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  #3  
Old 02-22-2000, 04:43 AM
Dart Dart is offline
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The simple solution is to convert to the mechanical linkage, vacuum problem solved.
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  #4  
Old 02-22-2000, 08:54 AM
Chris A Chris A is offline
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Can't remember where I saw it or where I read it but the six pack was not rated at 1000 CFM!! When whoever it was rated them they used a different rating system for 2V carbs. The actual cfm is around 850!! Anyone ever heard about this. Im not sure where I saw it but I KNOW ITS TRUE!!
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  #5  
Old 02-22-2000, 04:42 PM
Squad Squad is offline
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I thought the secondaries are 500 cfm and the primary 350 on a 6 pack.
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  #6  
Old 02-22-2000, 05:03 PM
turbododge turbododge is offline
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As I remember, the original "carburator God" rated 2 barrel carbs at 3.0 inches of water vacuum and 4 barrel carbs at 1.5 inches of water vacuum. The logic was supposedly that engines running 2 barrels would be more restricted and thus the carb would see more vacuum. 4 barrel engines would be less restricted and thus there would be less drop thru the carb. This is fine, as it does a better job of indicating what actual flow in the application is, but blows everything to hell when comparing 2 and 4 barrel carbs. There is a conversion, but I don't know exactly what it is at this time. The other thing to consider is that some 2 barrels will not flow fuel as well as a four barrel if the are seeing very low vacuum. I assume that this was accounted for in the six pack applications. I would think that the best system to open the secondaries on a six pack would be to have an actual air flow sensing system on the primary carb that is similar to the old Carter "AVS" valves used on some of their old 4 barrels. I personally have not had an opportunity to play with a six pack setup, so all of this is only hypothisizing.
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  #7  
Old 02-22-2000, 06:51 PM
Elwenil Elwenil is offline
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Squad is right. The 2300 series carbs were rated at 350 CFM for the center carb, while the outboard carbs were rated at 500 CFM. Oddly enough, Holley's current replacement carbs are the same for both manual and automatic cars, and are rated at 355 CFM for the center (P/N 0-4782) and 500 CFM for the outboard (P/N 0-4783).

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  #8  
Old 02-22-2000, 10:16 PM
paul paul is offline
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Six packs are adjustable.With the bigger cam and headers you're going to need more fuel at idle.If the end carbs have plugs over the idle adj. screws unplug them before you mount carbs.After running the engine and its still too lean at idle drill the idle restriction in the metering plates.Too get the end carbs to open sooner,you can restrict the kill bleeds to the diaphragms or block it off completley.If you block the kill bleeds off and the car is bogging off the line,then you can install stiffer springs in the diaphragms untill you get you're best 60' time.I got this info from an old super stock racer who ran a six pack.Good luck with that SIX PACK TO GO FAST!
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  #9  
Old 02-23-2000, 02:55 AM
turbododge turbododge is offline
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Just got home to take a look at my old reference materials for Holley stuff. The conversion for 2 barrel to 4 barrel rating is to divide by 1.414 so the 350cfm turns into 250 and the 500's turn into 350's to be at the same ratings as a 4 barrel. If you believe the standard airflow requirement formula, the center carb is good for 2550 rpm on a 340, and all 3 carbs together would get you to 9700 rpm. I have always thought that the formula is a bit conservative for high revving motors, but the six pack seems to have way more carb than you would usually need. If the six pack works the same as they describe the vacuum secondaries on a 4 barrel, blocking the kill port will make the secondaries begin operating sooner, but also slow down their going full open, as the kill port helps open the secondaries once they are started open by the primary flow. It appears that there are a limited amount of things that will affect when the secondaries open, and at what rate--diaphram spring, primary and kill port sizing, the relief size under the checkball to the diaphram, plus the engine vacuum capabilities. One thing that I have found is that if there are considerable engine modifications done that change the vacuum characteristics of the engine, just changing the opening point of the secondaries may not be the entire solution. You very well may need to do some modifications to the transition and main systems of both the primaries and secondaries to get the correct mixture at all operating parameters. This is of much more concern on a street driver than a drag car that only sees high rpm and full load. I would expect that with the small center carb on a six pack, that you would be able to get very good driveability on the street, but the large amount of secondary carb is going to be tough to tune for mixture because of the relatively low flow through each carb. There will be quite low velocity in the venturi and thus a weak vacuum signal to the main system. I have not tried it, but one of the new wide band oxygen sensor readouts might really make tuning a setup like this easier. This is all theory based on existing literature, if anyone has any real world experience, I would be very interested in hearing what really happens.
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  #10  
Old 02-24-2000, 02:10 AM
DAVE JONES DAVE JONES is offline
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Wow!, Thanks for all the replies and the research that you guys put into it. This has been a great help. After I get this animal going I'll repost and let everyone know how its going....thanks again...DAVE

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