4 barrel vs stock intake manifolds...

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firefighter1

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Hi guys,
I have a 71 dodge dart. It currently has a four barrel intake manifold with a 390 Holley carburetor on the 225 slant six. I am thinking about putting the old stock intake with the one barrel carb for economy and tuning purposes. What do you guys think? Pros and cons? Thanks.
 
Well, if the 4 barrel is set up right, you won't gain any economy by removing it. And there's almost no tuning you can do with the 1 barrel.
 
Agreed. A small 4 barrel is conceivably more efficient than a 2-barrel of similar size, if you operate off the primaries most of the time. Maybe even better than a 1-barrel, plus your choice in carbs is greater. Best is a spread-bore 4 barrel, with tiny primaries, but the only ones I know of (Thermoquad and Quadrajet) are really big like 800 cfm, so no help. If anyone knows of a small spreadbore, let us know.

That said, if you decide to sell your 4 barrel and 390 carb, I'm all ears. I recently got a 64 slant six and would love a 4 barrel aluminum intake to try some future things with fuel injection. I would swap you my single barrel intake, plus money. My carb probably wouldn't work since it uses a solid rod instead of the cable I remember on my 69 Dart 225. I travel between Sacramento and San Diego usually once a year, plus the Bay and Tahoe. Do I sound eager? I bet you are holding that intake close to your chest now.
 
A lot will depend on what's been done internally to the engine. If it's fairly radical with high compression ratio, race cam, headers, etc. going back to a 1bbl wouldn't help a bit. If it's a stock engine, the 1bbl might be the best setup.
 
A four barrel is not conceivably more efficient, it IS more efficient. It is so, whether you use the secandaries, or not. It's called volumetric efficiency.
 
Hmmm. Okay. You guys have given me a lot to think about. I still have a question though... Will my gas mileage be better with the single barrel intake and single barrel carburetor? My engine is all stock with exception to the intake and headers. Therefore, I thought it would run better or at least save me money at the gas pump....? Yes,no. What do you guys say?
 
It depends. If the jetting and bore sizes of the primaries of the four barrel you use are smaller than that of the one barrel, then yes, it could see better mileage than the one barrel.
 
I have the one barrel ,all stock set up on my 67 dart 225/ and am getting around 22mpg highway and city combined. . Have done a recent tune up with new points, condensor, dist cap and plugs... What kind of milage are you getting now
 
I might also add......you will be splittin hairs wanting "better" mileage. It's not like you're gonna make a huge difference. The slants were never really the MPG kings everybody made them out to be. In fact, a properly prepared 318 usually gets the same or even better.
 
StrokerScamp said:
It depends. If the jetting and bore sizes of the primaries of the four barrel you use are smaller than that of the one barrel, then yes, it could see better mileage than the one barrel.
Click to expand...

exactly... this is why i like mech secondaries... they wont open unless i tell them to... get it a little on the lean side from peak power (14.3-13.8) and you well run better than a one barrel, have more power than a one barrel...

what headers do you have, and what kind of exhaust setup?
 
Thanks guys. I will ponder the info for a while. I will probably switch back to the stock single barrel because of fuel economy and clearance for the stock starters. Hmmm....
 
ok,so if you switch from 1 barrell to 2 barrell,do you have to change manifold? I have carb issues rite now(just posted my problems under early A body) . My carb sucks rite now and wanna go to a new one,64 Dart 225
 
I switched from the stock motor with 1 bbl to a 4 bbl with a 390 Holly. I can't tell any measurable difference in mileage. I get 21mpg with the 4bbl. So since you already have the 4 I'd stick with it. That way if you make other power gains in the furture you already more air and fuel available, like new cam or head work. That would depend on what headers you have. My headers (not sure brand name) does not interferr with the starter.
@ honcho-Yes, switching from a 1 to a 2 bbl, you will need a 2bbl intake.
 
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