TeeWJay426

I mentioned my cousin's 73 Challenger Rallye before on this forum... it's an original 318 Rallye package car, but has a mildly worked '68 340 in it now, which until last year had a 6-pack setup on it. He's now running a 4-barrel, because the carbs on the 6 pack were worn and he just could never get it set up to run quite right. It has an automatic with a 3:91 8 3/4 rear. Pretty clean car all around, but not a show poodle by any means (translation.... he drives it like it was meant to be driven!)





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1 Bad Mirada

it looks nice and clean...
what intake manifold is that? an LP340?

Jeremiah 29:11

Wow.....very nice. I could tell because of the big rubber bumpers that it was a '73 just like I used to have.

He has to proud of that car.

He might check Holley careburetors since they have come out with new 6 pack careburetors for older muscle cars:

www.holley.com/types/O.E._Muscle_Car_Carbs.asp


"Holley still offers original list number Carburetors for highly collectible muscle cars. Over time these Carburetors have been nearly impossible to find, but no longer. These are NEW nearly exact reproductions of the originals. "

1 Bad Mirada

i dont think that the trouble is finding 6-pack carbs, but more so the problem is tuning them...ive seen ALOT of 6-pack guys swtich to a 4 bbl...

lear4406

I own a 70 GTX with a 440-6. The secret to tuning the sixpack hollys, is to take the out boards and go to the base. You will see the idle ports are coverd over in some metal. Dig this metal out and behind it you will see the idle needles. Spray some form of solvent into the port and work the needles out. Move the needles until they are free to turn in and out. Put the carbs back on and use a flexable standard screw driver to tune the idle as it sets and runs. tune at least 3 times. turning them in until they stumble. Then turnout until the idle smooths. Once the idle is smooth the vac secondarys must be cleaned and made sure of no vac leaks. I also made sure the vac lines are the same length and attached to the right vac port. The car should perform now and you will get a blast out of the 4barrels coming in. I hope this helps. Randy.

RLSH700

Also, don't 6-packs have an issue of really sucking down the gas a lot more than a four-barrel. I heard that the more carbs you have (the six-pack has three-two barrel carbs, a four barrel is just one carb) consumes more fuel but the number of barrels the carb has really doesn't matter. Is this true?

1 Bad Mirada

i do not know for sure, but a correctly tuned carb system will be no more or less efficient depending on the exact setup. I do not recall the exact CFM measures of the primary and secondaries of the "six packs", but figure that if you have a 300CFM primary, and twin 175 secondaries, you have 650CFM. I am using that number because thats what I ran originally on the mirada when my 340 was near stock. compare that six pack, properly tuned, to a 650 CFM 4bbl carb. they can both take in the same amount of air, so as long as they are both properly tuned, they should, in theory, use the same amount of fuel to achieve the optimum air to fuel ratio of around 14 to 1...

i would think that the six pack would also give you the option of dumping alot more fuel and air in at higher rpms when the secondaries open, which are only ideally open when youre under moderate to hard acceleration. when i want to change the size of my secondaries on the mirada, i have to change the entire carb, and in most cases the primaries are relatively a similar size to that of the secondaries. however, if you want alot more air and fuel at high rpm, it would seem to me that the secondaries could be changed, and tuned so that when they open, they would dump alot more air and fuel in...that would eat up alot more gas, but overall, a stock or evenly modified six pack shouldnt be any more inefficient than a 4 bbl carb...

again, ive not dealt with one, so if someone can correct me, feel free!

Jeremiah 29:11

Based on what I know, I agree with you assessment. Of course, the 6-pack when fully open will out perform a 4-barrel everthing else being equal.

1 Bad Mirada

based on the ability to allow for the increased air flow?

lear4406

The only reason a six-pack might use more fuel is because of the idle circuit for the 2 out board carbs.They have an idle circuit as well as the center carb. Holleys also have a secondary idle for the rear barrels. They are adjusted at the rear base. But flow under the throttle blades.