440 4-Barrel Swap - Advice?

[Dibbons]

It would be interesting to disable the two end carbs with the six pack, as is, and make some careful notes on MPG and throttle response. Then go to whatever four-barrel you want, and make some careful evaluations with that set-up. Report back to us and we can all have a lot more to comment about! Just a thought.

 

[PurpleBeeper]

It would be interesting to disable the two end carbs with the six pack, as is, and make some careful notes on MPG and throttle response. Then go to whatever four-barrel you want, and make some careful evaluations with that set-up. Report back to us and we can all have a lot more to comment about! Just a thought.

And if you do this, MAKE SURE to lock the end carburetors out, say zip tie them shut somehow. Just disconnecting the vacuum hoses will not disable them since they can still pop open with enough suction on the intake. Also, leave the linkage in place to pull them closed when you let your foot off the gas.

 

[rlem1977]

The car is a '70 Plymouth GTX with the four speed trans and a 3.54 rear.

I'm tired of tweaking this six pack to get it to run as well as I like, I'd like to try to try a four barrel. Agreed, a Holley double pumper would probably not be the best choice, I was thinking of a Carter AFB type carburetor, somewhat like what came with the 440 cars back in the day.

Any suggestions as to which manifold and carburetor would be the best choice for street driving and mileage?

Well, if you really want to go for mileage, and try to keep it Mopar-ish, grab a Carter ThermoQuad from a '71 (https://www.summitracing.com/tx/parts/sum-210232/applications) and a Edelbrock Performer 440 (http://www.edelbrock.com/automotive/mc/manifolds/chrysler/performer-bb.shtml) and try it out.

Personal Safety Disclaimer: To prevent myself from being stabbed, shot, maimed, drawn and quartered (I don't mean 4 pencil or crayola renderings), hung, tarred and feathered (or just tarred, I could do just feathered), tickled 'till I **** myself, or having Walter Chysler's ghostly apparition commanded to haunt me, by any member of this forum, understand that this is not a personal endorsement or recommendation for the above option. Good luck, have fun.

 

[BSB67]

I dont know about 40% but never had a 6pk setup. I swap back and forth from a 3310 and a 750 DP and the Vac carb gets a bit better mileage, Both average about 15.5 to 15.9 @ 60 to 70. In town and spirited driving is about $20 an hour.

I've never gotten better mileage out of a tuned vac sec Holley over its corresponding well tuned DP in any meaningful way. You need to be very deep into the throttle to even begin to actuate the DP secondaries.

The Holley 3310 is such a poor carb choice IMO. It does nothing well. A factory AVS or AFB can perform better. Stick with a dual plane, probably the regular Performer with serious consideration for using a spreadbore carb. You will be rewarded with both better throttle response, and better gas milage. If your cam is stockish, even consider the factory intake.

 

[66Satellite47]

My experience with a 3310-1 on low performance 383 (2bbl) motor was excellent with the DP4B Edelbrock manifold of the day & headers. The newer 3310 carbs may not the same. Secondary jet metering blocks were great. I never got an AVS to run well after rebuilding & trying numerous tuning efforts. However on my tow vehicle 360 a new Carter AFB (may be same as the Edelbrock) worked excellent with no tuning needed for several years. Your choice, Holley or Edelbrock whatever you think you tune.

 

[wagonman]

440 with 292/509 purple shaft, 906 heads, 4spd, 3.55 gears.
1. Holley 650 double pumper - 6mpg city, 8mpg highway
2. 750 Holley vacuum secondary - 8mpg city, 10mpg highway
3. Six pack - 10mpg city, 12mpg highway
All tests run the same summer within about 30 days of each other, similar driving. The double pumpers kill your city driving mileage.

My combo, 440 with reverse dome K-B for quench, 906s with bigger 2.14 and pocket ported. Comp XE268h-10 Eddy tm7. 323s and a 727 with a Hughes tight convertor. I picked up the convertor for cheep the app is for a motorhome. I think the gear and convertor are the biggest help for mileage. Would love to try the 6pk just for a compare and the WOW factor.

 

[rlem1977]

I have a '70 Plymouth factory six pack car, engine is stock with a mild street cam. (I believe it'a a purple stripe cam, was in the car when I got it.)

I'd like to convert to a four barrel for driveability and some level of fuel economy. Can anyone recommend a four barrel carburetor and intake? I'm concerned with driveability on the street rather than out and out performance. I'm not overly concerned with a stock appearance.

(I'm tired of tweaking and tuning this six pack to get it to run correctly, I just want to drive. I'll keep the six pack and pass it to the next owner when that day comes.)

Might look at FiTech 3x2 Fuel Injection. Once set you won't have to "fiddle" and will probably get better fuel economy.

 

[wyrmrider]

Tune the 6 bbl best answer
if not TQ is the best carb
and AVS second best

 

[MoparHonda]

Thank you very much for all your responses, this has all been very helpful, I'm just frustrated with tuning this six pack....

 

[WileE]

I've never gotten better mileage out of a tuned vac sec Holley over its corresponding well tuned DP in any meaningful way. You need to be very deep into the throttle to even begin to actuate the DP secondaries.

The Holley 3310 is such a poor carb choice IMO. It does nothing well. A factory AVS or AFB can perform better. Stick with a dual plane, probably the regular Performer with serious consideration for using a spreadbore carb. You will be rewarded with both better throttle response, and better gas milage. If your cam is stockish, even consider the factory intake.

I'm curious as to what you base your view on the 3310. We did many a carb/manifold swap on many different makes, and this carb was a very popular choice, and not one case did it perform worse than the stock factory setup.

 

[MoparHonda]

WileERobby, what intake manifold did you use with the Holley 3310? Was it the Edelbrock Performer?

 

[WileE]

I did these back in the 70 's on customers cars, all different makes and engines. We used intakes by edelbrock ( tarantula,torker, streetmaster), Weiand, Offy, etc. On street cars, the 3310 was a good all around vacuum secondary carb, just jet it to whatever that particular engine needed.

 

[BSB67]

I'm curious as to what you base your view on the 3310. We did many a carb/manifold swap on many different makes, and this carb was a very popular choice, and not one case did it perform worse than the stock factory setup.

Right. "The" go-to-carb.......in the 70s. 3310 was a household name. My mom probably knows what a 3310 is. It was simply a 1970s, budget, universal carb. Question to you. Do you have any data that shows the 3310 outperforming a tuned factory 1 11/16" primary/secondary AFB or AVS on a stockish 440 or 383? How about a Chevy, Pontiac Ford? I do not. Not saying never, But I have not. The exception of Holley data by Holley. I do know of cases where someone had a AVS or AFB that did not run well because of a problem, and they would just buy a 3310 and were much happier.

I currently have a bunch of carbs, including two or three 3310s, not to mention all the ones that I messed with in the 70s that are either now gone, or were someone else's. So this is the basis of my conclusion. Of all of the 3310s, my "original" 3310 with the rear metering block and secondary down leg boosters runs the best.

I have done several back to backs track events with a stockish 440 and 383 with 3310 and the big AVS/AFBs, and the Carters were either the same or just slightly quicker. I've also done the same with the 3310 and 4779, and the 4779 was always faster, even on a stockish BB Mopar.

 

[WileE]

Right. "The" go-to-carb.......in the 70s. 3310 was a household name. My mom probably knows what a 3310 is. It was simply a 1970s, budget, universal carb. Question to you. Do you have any data that shows the 3310 outperforming a tuned factory 1 11/16" primary/secondary AFB or AVS on a stockish 440 or 383? How about a Chevy, Pontiac Ford? I do not. Not saying never, But I have not. The exception of Holley data by Holley. I do know of cases where someone had a AVS or AFB that did not run well because of a problem, and they would just buy a 3310 and were much happier.

I currently have a bunch of carbs, including two or three 3310s, not to mention all the ones that I messed with in the 70s that are either now gone, or were someone else's. So this is the basis of my conclusion. Of all of the 3310s, my "original" 3310 with the rear metering block and secondary down leg boosters runs the best.

I have done several back to backs track events with a stockish 440 and 383 with 3310 and the big AVS/AFBs, and the Carters were either the same or just slightly quicker. I've also done the same with the 3310 and 4779, and the 4779 was always faster, even on a stockish BB Mopar.

Do I have any "data" ? Seriously ? The only data I know is real-world, real-life experience. But you say your experience is the Carter's were the same or slightly better than the Holley... ok, I can accept that. But that's a far cry from being " a poor choice & it does nothing well "

 

[BSB67]

Do I have any "data" ? Seriously ? The only data I know is real-world, real-life experience. But you say your experience is the Carter's were the same or slightly better than the Holley... ok, I can accept that. But that's a far cry from being " a poor choice & it does nothing well "

Your're right. I could have probably chosen better words. If you want to spend your money on a new carb that is marginally adequate, the 3310 is a good choice. Personally, I would rather not do that. Honestly, based on my experience, I cannot think of a case where I would recommend a 3310.

I've been planning, for far too long, a mild 440 build that I would spend time track testing the pile of carbs and intakes I have laying around. Where does the time go.

 

[WileE]

Hey, many people rip thermoquads, but I personally like them. Many a Mopar equipped in the 70's

 

[BSB67]

Hey, many people rip thermoquads, but I personally like them. Many a Mopar equipped in the 70's

I like TQs too, as well as QJets....gasp.

 

[WileE]

I like TQs too, as well as QJets....gasp.

QJet is (was) a good carb. Even found their way on Mopars.

 

[MoparHonda]

RLem1977, I licked on your link on the carburetor, it shows info for a 340 engine, I'm working with a 440, are you sure you have the correct link?

 

[Dennis H]

Recent trip to Los Angeles, my pal w/6 Pak 'Cuda got better mileage than my 850 Demon. Like the Demon though. Need to hook up vacuum advance for more fuel range.