6 Pack vs. 650 4BBL?

[68 HEMI GTS]

I like your throttle cable clamp, very nice.
How's that linkage working for you?

Seemed to work real good! Didn’t get a whole lot of drive time on it. I used some old AN line and was having some debris issues. I plan on revamping the fuel line set up and getting the carbs dialed in better this year. I may add idle circuits to the outboards also, it’s a little boarderline on the idle with just the peep holes.

 

[68 HEMI GTS]

318 I am going to try the 750 and see what it does performance wise. Here is a picture of the LD340 - Had it cleaned up and powder coated. Full engine picture is engine completed.

View attachment 1715121376

View attachment 1715121377

Stay away from a DP on your combo. A vacuum secondary carb will Work better unless you have a wild converter. A normal 3310 vacuum secondary carb would be my choice on that intake. If we’re saving money as every one suggests, you can pick up a used one very reasonable and throw a kit at it. It’s gonna perform just as good or better as any of these fancy carbs all these guys are throwing out there. Some of the aftermarket carbs have a bit more tunability. It doesn’t do 95% of people any good because they don’t have the knowledge, parts, tools, or dedicate the time to really dial them in. I think the LD340 should work good. It you wanna race off the line that little 340 needs more gear. IMO

 

[318willrun]

Eddie, my opinion and experience is this: I've played plenty of games at the dragstrip with combos similar to yours. I've brought carter 625 AFB's, 3310 Holleys, to try and improve over my 750 dp. NONE could match the E.T. Some came within a .1, but none even could improve on the 60 ft time. Ready for this? The one combo that would run the best against the 750 dp on a LD340 intake was the factory cast intake and Thermoquad. trust me, you need to know how to tune a TQ, but it did the best against the rest.
I do agree, the 3310 would be a nice improvement over your current carb, I'll say I could make the dp improve over it. IF you go vac sec, I really like the 770 Street Avenger.

 

[brian6pac]

Seemed to work real good! Didn’t get a whole lot of drive time on it. I used some old AN line and was having some debris issues. I plan on revamping the fuel line set up and getting the carbs dialed in better this year. I may add idle circuits to the outboards also, it’s a little boarderline on the idle with just the peep holes.

I see you ran the fuel line out to the front, if you use a electric pump just run it up the fire wall and come around the back of the carbs, it keeps more heat off the fuel line.

 

[68 HEMI GTS]

I see you ran the fuel line out to the front, if you use a electric pump just run it up the fire wall and come around the back of the carbs, it keeps more heat off the fuel line.

I always keep them away from the firewall for safety reasons on my own cars. Just personal preference I suppose.

 

[MOPAROFFICIAL]

Understood. How about the the 750 Demon on top of the LD340? Thank you

That will out perform a 6 pak.
Always comes down to one thing, what carb setup is on the fastest or faster drag cars of the world...hint...its not a 6 pak.

 

[MOPAROFFICIAL]

I see you ran the fuel line out to the front, if you use a electric pump just run it up the fire wall and come around the back of the carbs, it keeps more heat off the fuel line.

As all the heat from the motor is blown backwards into the firewall and you say to mount the line there because it's cooler...lol.
If you'e worried about fuel temp, buy fuel cooler can and mount it to the core support or simply insulate the hard line running along the rail.

 

[brian6pac]

I always keep them away from the firewall for safety reasons on my own cars. Just personal preference I suppose.

My 70 cuda was a 4 speed and I did run the brake line and the fuel line outside the frame rail and brake line across the front of the K member, but with the automatic car It doesn't bother me as much.

 

[brian6pac]

As all the heat from the motor is blown backwards into the firewall and you say to mount the line there because it's cooler...lol.
If you'e worried about fuel temp, buy fuel cooler can and mount it to the core support or simply insulate the hard line running along the rail.

I was talking about radiant heat from the headers but if the line is outside the rail it really doesn't matter I guess.
I did run a cool can back in the day and I think I still have the moroso one with the corkboard around it.

 

[Eddie348]

Stay away from a DP on your combo. A vacuum secondary carb will Work better unless you have a wild converter. A normal 3310 vacuum secondary carb would be my choice on that intake. If we’re saving money as every one suggests, you can pick up a used one very reasonable and throw a kit at it. It’s gonna perform just as good or better as any of these fancy carbs all these guys are throwing out there. Some of the aftermarket carbs have a bit more tunability. It doesn’t do 95% of people any good because they don’t have the knowledge, parts, tools, or dedicate the time to really dial them in. I think the LD340 should work good. It you wanna race off the line that little 340 needs more gear. IMO

Hemi GTS - Thank you what gear do you suggest?

 

[Eddie348]

Eddie, my opinion and experience is this: I've played plenty of games at the dragstrip with combos similar to yours. I've brought carter 625 AFB's, 3310 Holleys, to try and improve over my 750 dp. NONE could match the E.T. Some came within a .1, but none even could improve on the 60 ft time. Ready for this? The one combo that would run the best against the 750 dp on a LD340 intake was the factory cast intake and Thermoquad. trust me, you need to know how to tune a TQ, but it did the best against the rest.
I do agree, the 3310 would be a nice improvement over your current carb, I'll say I could make the dp improve over it. IF you go vac sec, I really like the 770 Street Avenger.

318 - Thank you looking at all options now. Looking at taking the car to get trans rebuilt new shift kit an TC recomendations as well

 

[Eddie348]

I actually bought one of the 625 demons when they came out 3 or 4 years ago, it is a nice carb, took care of my heat issues.
They do have one drawback, you have to dissemble the carb to put the mopar throttle linkage on, and the stock linkage will not work, you need to buy the one in their instructions.

Thank you

 

[Eddie348]

60 fts,TM,(TorqueMultiplication),weight reduction, and cylinder pressure.
I'm assuming "off the light" means off the stop light and not the tree. In which case traction is gonna be your biggest issue. Then TC.Then gears. Cylinder pressure you may already have lots of.And your car is already one of the lightest A-bodies around.
>All the gears and TC in the world won't help you at 300HP if you can't make it stick. So 60fts is first.
>The TC will let the car launch at a higher rpm where there is more power, which, with lack of traction, just makes things worse.
>The gears, you need, to put down more average hp during the running distance. If you can use up 2 gears from zero to 60, instead of 1 gear, then the average power goes up, and that gets you closer to teaching 'em a lesson.
>So 60fts is first.

So what approcah would you recommend? Changed the leafs to SS prings aleady, installed a pinion snubber etc. Thanks

 

[Eddie348]

It is true that "generally" a good tuned single carburetor will run better and out perform multiple carburetors.

That said, if you know how to properly tune a six pack, it is not true. The reason is because the center carburetor is a mechanical carburetor. It has its own accelerator pump and it is connected directly to the car's throttle linkage. When the accelerator pedal is depressed, the center carburetor opens. Not true of the outboard carburetors.

Both the outboard carburetors. are vacuum secondary units. They only open as the engine demands it. If properly tuned and adjusted, the six pack is nearly unbeatable. Do the math. You're talking about a 600 CFM carburetor and trying to compare it to an 1100 CFM six pack. Ain't happenin. Some people say they spec out at "only" 900 or so CFM. Even still, the six packwins out heavily when properly tuned.

The keyword in all this is "properly".

As noted in a couple of posts here already, lots of racers use them. Lots of racers won using them. Lots of records have been made......and broken with six packs.

All of this said, the exact polar opposite can be true if you do not learn how to tune them. They can be your worst nightmare. If you really want to run one, find someone who has REALLY run them. Pick their brain.....BEFORE you buy a six pack. That way, you will know for sure it is is something you want to put that much effort into.

Rusty good morning. Thanks for the continued support on my venture. Did some tuning this year and the car still in my mind reached its full potential.

 

[318willrun]

So what approcah would you recommend? Changed the leafs to SS prings aleady, installed a pinion snubber etc. Thanks

What do you have for tires? Traction is the name of the game if you are horsing around at stoplights, or racing 1/4 mile. It all starts with a good set of drag radials....

 

[Eddie348]

Currently I have red lines -
Wheel Diameter:14 in.

Tire Size:F70-14

Sidewall Style:Redline

Tire Construction:Bias-ply

Tire Diameter Range:26-26.99 in.

Tire Diameter:26.20 in.

Section Width:8.30 in.

Tread Width:6.70 in.

Minimum Recommended Wheel Width:6.00 in.

Maximum Recommended Wheel Width:7.00 in.

 

[318willrun]

Currently I have red lines -
Wheel Diameter:14 in.

Tire Size:F70-14

Sidewall Style:Redline

Tire Construction:Bias-ply

Tire Diameter Range:26-26.99 in.

Tire Diameter:26.20 in.

Section Width:8.30 in.

Tread Width:6.70 in.

Minimum Recommended Wheel Width:6.00 in.

Maximum Recommended Wheel Width:7.00 in.

yeah, you might want to consider something better for traction with your tires.

 

[rumblefish360]

The biggest problem I see here is the comparing of the stock style Holley 2bbl. carb trio to the heavily modified race Holley. (This is also a problem between the Carter/Edelbrock vs. Holley)
CFM wise, the 6 pack delivers in the 950 area cfm of air and fuel (when the conversion is made). VS what ever 4bbl. your putting it against. Just on cfm alone it has the ability to make more power. So the next thing would be...

The 6 pack intake could be updated to a more modern well thought out design. The small block intake has 3 towers! That go down to a the dual plane runners. Air and more so fuel do not like to take turns. And there are 90* turns involved.

This ancient intake could use some modern help!

The modern 4bbl. intakes have only 1 disadvantaged to them and that would be the central location of the carb. The air and fuel have to make a long turn. And it is far better than the 6 pack! And only 1, but not so bad over all 90* turn.

Between a single plane and a dual plane, the single should be easier to modify and correct to equalize the flow to equalize air and fuel mixtures over the dual plane.

For a intake released in ‘70, (small blocks) it is still a hell of a Performer.

You wanna go fast? A single carb on top of your intake is the easiest and cheapest way to go.
If you want WOW, pizazz, BAMM! flexibility for your street/street stripper and the money is not a concern, a 6 pack is it. Dual plane dual quads are also a very do-able way as well. But are super difficult to find.

 

[68 HEMI GTS]

Hemi GTS - Thank you what gear do you suggest?

4.10 gear is a good choice, you’re tire limited anyway on a 69 dart. Now it you step the gear up, get a good high stall converter such as a PTC the game begins to change. A DP becomes an option.

 

[yellow rose]

As I've said before, if you use a 3310 and it's faster it's a tune up problem. Most of the time the secondaries don't open, or barely open. Might as well use a big 2 V carb.

A 3310 is a boat anchor. Don't waste your money on ANY vacuum secondary carb. If you are going to spend money, call BLP or mark Whitener or thumperdart over on moparts.

Quickfuel is now owned by Holley and it shows.

Spend your money once. No vacuum secondaries and a tune able carb. Air bleeds and idle feed changes are simple. I have faith that you can learn it if you want to.

 

[RustyRatRod]

That will out perform a 6 pak.
Always comes down to one thing, what carb setup is on the fastest or faster drag cars of the world...hint...its not a 6 pak.

But you also have to look at that from a class perspective. Six packs have dominated certain classes. That cannot be denied.

 

[rumblefish360]

That will out perform a 6 pak.
Always comes down to one thing, what carb setup is on the fastest or faster drag cars of the world...hint...its not a 6 pak.

An LD-340& a 750 faster than a 6 pack?
Ohhhh ho ho man a know a few locals will laugh there *** off at you for sure!

The second part of the quote about racing is an unfair match up.
And you know it. LMAO!

 

[68 HEMI GTS]

I like mechanical carbs as much as the next guy but, this BS about vacuum carbs not working is unreal. So is some of the other nonsense in this thread. The idea is to build combos and parts that work together. I remember now why I avoid these kind of threads.

 

[RustyRatRod]

I like mechanical carbs as much as the next guy but, this BS about vacuum carbs not working is unreal. So is some of the other nonsense in this thread. The idea is to build combos and parts that work together. I remember now why I avoid these kind of threads.

Yeah, Larry Shepard recommends the VS with an auto and the DP with a manual. While these rules are only meant as a guide, they work pretty well, even today. I would challenge anyone here to have the knowledge Shepard does, even though a lot of what is written in the engine book is dated, it is not incorrect.

 

[brian6pac]

Unfortunately Larry Shepard is no longer with us and his shop is about 10 miles from my house
I used to talk to him when I was a young in the 70's, him and a guy named John Barker who was a engineer and a die maker at the twinsburg plant that was the max wedge guru. All the racers around called Barker the professor because he knew so much about the math that went into building engines.
As 68 hemi says, I was talking to the guys at Indy cyl heads about a year ago and they claim they have made a 440 with the modman manifold with vacuum 6 pack make over 1000 HP.