Thanks olafla, I'm not really set on a new manifold. My current BBS is on its very last leg and I figured I might as well upgrade to a Super Six rather than getting another BBS or 1920 and upgrading later. However, I can't seem to find a Super Six and now I'm thinking I'll just go straight to a small 4bbl.

Frank, you are tempting me... I really like the design of the new short runner intake, seems like the runners are just about equal. Can you explain the heater box accessary a bit? I'm guess it probably won't work with stock exhaust heat?

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'66 Dodge Dart

hi, this is a holley 80457s 600 cfm with sec metering block kit on a stock 225 that i had used on a 1968 chrysler 300 with a 440. im redoing 2 slants, but getting this settup ready for the engine in the "acid dip bh block post". i just drove 2.25 hrs each way on sat to lebanon new york to the dragstrip to try it out. ran great. i thought bog city with a 600 and burn dirty. no bog, great mileage, and works with fac ex manifold. i have stock holley 1 bbl kickdown hooked up with a link from offy in the picture. im glad i went to a 4bbl . ronnie

Josh
The Aussie Speed manifolds are ALL equal length runner design. The long runner one has a square box that can be mounted in any direction under the plenum area via welding or epoxy. This then connects to the water system like a heater hose. (This is the same way as a Clifford is heated).
The short runner manifold is supposed to have the heat box built into the bottom instead of externally mounted.
I have not, nor have I heard of, any problems with the epoxyed on version. And I like it flexability.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

chuck im kicking this post up to help you . this carb had 60's in both pri and sec but after checking plugs and looking at pistons/chambers with a borescope, i am putting 65's pri and secondary for this years driving. engine was too lean for my eyes. 65's might be too much,but i have to try/test first. ronnie

If you want a 4-bbl carburetor, you need a 4-bbl intake manifold. Reworking a stock 1-bbl manifold to make a 4-bbl carb fit, is maybe possible, but it is not a very good solution.

Regarding carb choice:
If we look at the extremes, several members have run a big 850 or 1000 cfm 4-bbl Carter ThermoQuad (TQ) on the SL6 with great success, and in the other end of the 4-bbl spectrum, many members have had problems adjusting a small Holley 390.

The reason is that there is a major difference in carburetor design that should be taken into consideration when talking about 4-barrel carbs. The TQ, and also the Edelbrock carbs - which build on an old Carter design, has a counter weighted - or counter sprung, air door - or air flap, above the secondary throttle plates. That flap opens for the air supplied to the secondary venturi circuits, according to the force from the amount of air sucked into the engine. That makes the need for air regulate the amount of fuel that is supplied to the secondaries. Less amount of air through the secondary venturis give less air speed, which gives a lower vacuum signal which gives less fuel. Simple and ingenious! The TQ primaries are very small at 1-3/8" or 1-1/2", and give excellent starting, idle and low-speed driving capabilities. The secondaries are huge mechanical operated throttles. Two giant 2-1/4" diameter throttle plates, but without the air door above them opening from the force of the air rushing in, the secondaries do not deliver anything at all! That is the reason for the factory using that same type of carb on smoggy 318 engines, as well as on 440 hi-performance models.

An Edelbrock carburetor, that is built roughly on the same principles, is perhaps the ideal type of carburetor. The 500 cfm size is perfect for a smaller engine, because when it is adjusted to run properly at idle and on the primary circuit, the secondaries will self-adjust according to the momentary need, until the limit of the carb is reached. If I was about to buy a new carb, the 500 Eddy would be first on my list.

My personal choice - because I already have some and I really like them, for my project engine, is the Autolite 4100, size 1.08, 4-barrel square-bore (same size throttle plates on primaries and secondaries), with annular boosters, and vacuum operated secondaries, mounted sideways on an Offenhauser intake. That specific carb size flowed 441 cfm in a flow bench test made some years ago, instead of the 600 cfm that Autolite claimed! It was originally fitted to 260 and 289 Ford V8 engines, but the same size was also used on big 390 engines.
In theory, the flow capabilities should make it almost ideal for a well-flowing SL6, what happens in real life remains to be seen.

Olaf.

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Aspenized

I actually got better economy with a 465cfm Holley than I did with a BBD, I also went faster with the BBD that the 465cfm Holley on the same engine, 9.8:1 and a slightly hotter than stock cam.

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Glad to see this post getting a little more attention since full Super Six setups are so rare (or overpriced) these days.

olafla, I know I would need a 4bbl intake, currently I am leaning heavily toward the AussieSpeed short runner intake. And your info on the designs of the Carter and Edelbrock carbs vs the Holley is very interesting.

I wonder if any members who have actually run the Edelbrock 500cfm can chime in? Any reports on millage, performance, tuning issues/successes, etc are great (especially when compared to a Carter BBD or Holley 390).

70valiant, very interesting. I'm not familiar with the 465cfm Holley, although if you got better millage I would assume its sequencial and that the primaries are smaller than that of the BBD? Also, any ideas on why performance hit when compared to the BBD, perhaps secondaries don't fully come on?

Has anybody tested the AussieSpeed short and long runner intakes and have any reports on their differences? Frank maybe you can give a little sales pitch?

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'66 Dodge Dart

I believe the secondaries never worked properly(at all?), or there just wansnt enough vaccum signal with the stockish cam. At one point my brother in law reached under the carb and worked the secondaries by hand and it reved up and made an awesome sound I had never heard it make before. The difference in milage was not pronounced. I got a best of 21.1 with the BBD and could get almost 23 with the holley. The car was a beast with both carbs. Its been over 2 years and I still miss my Valiant.

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Josh, I was wondering if you had read the other Josh’s thoughts on /6 carburetion?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Josh, also take into consideration the difference in how 4-bbl manifolds are constructed. The Offy is bolted to the stock exhaust manifold, so that you very quickly can get the necessary heat under the plenum chamber. The Clifford and Aussiespeed manifolds use a bolt-on heat box fed by hot water from the cooling system. The climate you live in, dictates how long the warm-up period for the engine is. If you frequently run your engine in prolonged choke-mode, the Offy may be a better choice in the warm-up period. I am not familiar wih the differences once the engine is fully heated, with regard to the efficiency of the water heating, somone running the Cliffords and Aussiespeeds must share their experience in that respect.

There is also a slight difference in how the intakes perform, as I understand from other members' writings here, the Offy has some more grunt on low and medium engine speed, while the Clifford delivers a bit more in the high-rev range. According to Aussiespeed themselves, their manifold delivers over a wider range, and combines the characteristics of both the others.

When used with a automatic transmission, you also need a kickdown mechanism. A cable operated kick-down setup is more flexible, and also allows you to mount the carburetor sideways on the manifold, for a slightly better fuel distribution.

As the oil price seem to reach new heights, using every little trick to improve the efficiency of the engine will pay off in the long run.

Olaf.

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Aspenized

Thanks for sharing the experience 70valiant.

olafla, lots of great info, thanks!

wjajr, yes I've read it a few times, and Josh did an excellent job, although I wonder if there isn't more info and tests that can be add to the article. The 4bbl that olafla suggested is only mentioned in passing and mentions that it probably wouldn't produce decent millage at idle/low speeds.

If anyone has actually ran the a 500cfm Carter/Edelbrock, would love to hear your experience and engine build!

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'66 Dodge Dart

Thanks for the kudos. It's perfectly possible, reasonable and proper to add more information to the carburetion article. What we have to be careful with though is poor comparisons. It's not valid to remove a thoroughly whipped Holley 1920, put on a good BBD or Weber, or Edlebrock and say "OMG people! I gained 60% in fuel economy and took 3 seconds off my 1/4 mile ET. The article presupposes that all the carburetors used are in good condition and tuned well.

One of the largest problems with alternative carburetors is their existing calibration not being close to what our engines need. If the fuel/air mixture curve isn't appropriate then the jetting will be compromised at some point. Usually the case is we put in a larger main jet until the car drives reasonably and then suffer excess fueling under much of the engine's operating points increasing pollution, fuel consumption and engine wear.

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Joshua

I ran an Offy, 390 Holley, Clifford headers, 3500 stall converter, and 3.91 gears with a completely stock '80 Volare longblock in my '66. It went 16:20's.

Would I run a 390 on anything w/o some gear behind it? Not a chance.

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Official Cookie and Mater Tormentor.