is the truck holley two barrel more cfm than the 318 carter two barrel and if so is there an adapter to fit it on my stock 2 barrel manifold on my /6

duck@hsnp.com

Yes, there are some larger 2 bbls out there but as you noted, most all need an adapter plate and some linkage mods to work.

Here is a post from below on the subject, go to that date or use the search for more...
DD

Re: A Bigger BBD carb for your Slant 6 !!!
Posted By: JKKo
Date: Friday, 8 June 2001, at 11:21 p.m.

In Response To: Re: A Bigger BBD carb for your Slant 6 !!! (Craig)

I did a carburetor swap yesterday. I have a super six setup from '79 or '80 Dodge Aspen in my '66 Dart. My engine is rebuilt about 2 years ago, and there are some extras; An MP 244 degree cam and Dutra Duals with 2 separate 2" pipes. The junked carb gave me several problems during the years. It was clogging its idle jets with something that was coming from itself. There has always been a quality fuel filter before it. I cleaned it several times, installed a rebuilt set and so on.

That carb also had a very worn throttle blade(s) shaft, which I tried to get fixed with some home made machined bushings. The result was somewhere below average, not because of the bushings but the bad basement. Anyway, I was hunting all the time something better to replace that old one.

Here (north Europe) we do not have junkyards full filled with excellent donors...

OK. I had some luck, and I won one BBD from ebay. It was a brand new NOS carb, Carter BBD, list 6150S. Originally made for '72 318 I have been told. It came 7 weeks from NJ with surface mail, which was an accident from seller. There was no emission stuff at the carb (looks better to me), and what is the most important is it has noticeable BIGGER venturis that the 225 engine BBD.

It vent to its place with small hardware mods, the linkage was a little different between these 2. The engine was running smooth idle with the carb straight from the box. (It has been there something like 20 to 30 years waiting to get installed...)

During the tests I feel an improvement which was close as big as I had when swapping the 1bbl carb to Super Six Setup or when swapping the 1 7/8" single exhaust with Duals. I recommend this swap if a good carb from 318 is available. It is a good idea to measure throttle bores and venturis, because there could be several versions in different cars, years, and market areas.

JKKo
:
: I would have no idea of a "casting
: number". When I was looking around in a
: local salvage yard I found several early to
: mid 1980's vintage Dodge trucks with Carter
: BBD carburetors and I thought the engines
: were 318's since the 360's used to use
: Holley carbs with a bigger bolt pattern than
: the 318's used. However the underhood
: emissions decal said 5.9 liter (360) engine.
: At first I thought someone swapped a 318
: engine in place of a 360. But there were
: just too many that way. Eventually I
: remembered seeing in a Dodge Truck service
: manual that there was a BBD used on a 360
: engine. I suspect they did this so they
: could use the same intake manifold on the
: 318 and 360 engine and not make a separate
: 360 intake anymore.
: Anyway......I can not find that manual right
: now. I remember it specified a larger
: venturi size for the BBD on a 360. I'll try
: to remember to post that information here
: when I find the manual.

There's kinda no such thing as "the truck 2bbl" or "the 318 2bbl". There are many, many, many different "sizes" of 2bbl carburetor used on Chrysler small and big block V8 engines. How do you want to talk about "size"? There's bolt pattern (small bolt 2bbls like the Carter BBD 1.25 and Stromberg WW3, used on small blocks and 2bbl 225s; big bolt 2bbls like the Carter BBD 1.5 and Stromberg WWC3, used on big blocks). But within those, there's a bunch of different venturi sizes, flow rates, calibrations...

Unless you're racing or spend all your time at WFO ("Wide Open Throttle" ;-{)} ), the biggest determinant of the driveability and performance of your setup is not going to be the maximum flow rate (CFM) of the carburetor. Rather, the condition and calibration of the carburetor is most important. Some of the "smog" 2bbls have very "doggy" and lean calibrations, with slow/lean fuel curves and slow/late vacuum spark advance signal. Some of the giant big block 2bbls have huge venturis that give good WFO flow rate (high CFMs) but don't support start/idle/low-speed/around-town type of operation from smaller engines since the flow velocity through the carburetor gets too low to create good fuel vaporization.

And then we can talk about venturi design! Simplex, duplex concentric, triplex concentric...and Holley's "venturi ring" in their Economaster carburetor, which is designed to give good vaporization even at low flow velocity. I've wondered about using an Economaster carburetor meant for a big block on a slant-6 in extremely demanding (truck, light race) conditions, but never tried it. Adaptation would be required to install the larger carb on the smaller bolt base.

I've had good success building Carter BBDs for Slant-6s using parts from numerous different carbs...some from V8 carbs, some from 6 carbs, to get each system to do exactly what I want it to do, when I want it to do it. But you really have to be a geek like me or Doug to get into the research and experimentation this approach requires.

I've just installed a Holley Economaster meant for a 1970 318 truck (I am a big fan of manual chokes) on my '62 225 Lancer. The report (it's in Denver) is that it starts and runs. Beyond that? Don't know yet!

DS


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