440 4-Barrel Swap - Advice?

[MoparHonda]

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.)

 

[moparedtn]

440? 340?

 

[davek]

sounds like your center carb needs rebuilding. If its a vac set up you can get good mpg. 440s really dont get great mpg.What are you shooting for on mpg? Is your car a auto or 4spd?Rear end gears? Need more info.

 

[Lionized]

sounds like your center carb needs rebuilding. If its a vac set up you can get good mpg. 440s really dont get great mpg.What are you shooting for on mpg? Is your car a auto or 4spd?Rear end gears? Need more info.

Absolutely this. Your Six Pack should give you better mileage, in proper tune, than a four barrel set-up. If you don't have a lead right foot you're cruising around on the center carb 99% of the time.

 

[WileE]

Yeah, you can go get a Holley 3310 on a Edelbrock performer Rpm manifold. But why ? If your carbs are correctly setup, assuming stock vacuum secondaries, it's really bulletproof.

 

[towtruckAl]

had a 440 six pack in the seventys got decent milage running on centre . used to disconnect the 2 end carbs during the week going to work incase the old speed devil whispered in my ear .

 

[WP29440SE]

first thing that came to mind was that you're attempting to stuff a 440 4 barrel in a honda

 

[Garys1969RR]

My 440 six pack RR ran perfectly. The intake and carbs were brand new, a couple years ago. In new condition, these units perform very well. As has been said, a good tune up on the center carb, with moderate driving, should get you decent gas mileage. If you are still determined to go to a 4 barrel, the Performer RPM with a 3310 Holley vac secondary, should work well. That's a good all around choice for a street car.

 

[HEMI-ITIS]

I'm sorry,but the 6bbl is the ****!!!

 

[66Satellite47]

The 6bbl takes some effort, but they can be made to run really well. The factory settings were not optimal. End carbs need attention. Remove the plugs covering the end carb idle mixture screws, open them up about a 1/4 to 1/2 turn. With a bigger cam you may need to increase the idle speed screws a bit, they're under the base plate. If you don't stand on the pedal you're running on a small 2bbl so mileage is as good as most 4bbls. Stock jetting on the 6bbl (my '70 carbs were the best) worked well for me. A 4bbl can work pretty darn well too. Torker or a TM-7 will work great with a 750 cfm Holley, vacuum or mechanical. Mechanical may take a little more tinkering.

 

[PurpleBeeper]

Don't do it.....I've run mpg testing on a 650 double pumper, 3310-style 750 vacuum secondary and a six pack. You will be giving up about 20% mpg loss going to a 4-barrel....giving up 40% if you go with a double pumper (almost cutting your gas mileage in half)

 

[wagonman]

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.

 

[MoparHonda]

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?

 

[68 HEMI GTS]

If you’re constantly messing with the six pack it has issues. Should be trouble free and hands off after its set up correctly. And honestly I can’t see any single 4 doing any better than that small little 2 barrel. Sounds like you need to go back to a stock cam. That’ll improve things.

 

[SlinktRR]

800 AVS runs well on a 440. If you don't want it, I'll gladly use the 6 pack.

 

[MoparHonda]

Agreed, the stock cam would probably be the best choice and I wish it had the stock cam.

BTW, the carbs have been rebuilt, but still does not run as well as I'd like. I'm just driving around the streets, I'm not putting a foot into it so to speak.

Thank you for all your replies thus far, do we have a consensus that the Holley 3310 with the Edelbrock Torker manifold is the best choice?

 

[MoparHonda]

Thank you, I'll look at the Carter 800 AVS.

I plan to keep the six pack and pass it on to the next owner of the car when that time comes.

 

[SlinktRR]

the best choice is whatever you or your mechanic can tune. If it was me i would find someone who can tune 6bbl, because the benefits of that setup far outweigh the negative.

 

[PurpleBeeper]

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.

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.

 

[WileE]

Agreed, the stock cam would probably be the best choice and I wish it had the stock cam.

BTW, the carbs have been rebuilt, but still does not run as well as I'd like. I'm just driving around the streets, I'm not putting a foot into it so to speak.

Thank you for all your replies thus far, do we have a consensus that the Holley 3310 with the Edelbrock Torker manifold is the best choice?

No, use a dual -plane intake for your intended use.