360 2v vs. 383 2v

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Princess Valiant

Princess Valiant

A.K.A. Rainy Day Auto
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Soooo is there much difference in flow between a 2 barrel carb from a 360 and a 2 barrel from a 383??

I have a 2 barrel from 72 360 and a 2 barrel carb from a 68 383.

Is there much if any difference??
 
I would think the difference would be splittin hairs.
 
The 4 barrel will get decided better fuel mileage. But I get the feeling you're wanting to use stuff already layin around and that's cool too.
 
gm makes a 435cfm/ called 500 cfm by us restricted class racers Rochester 2 barrel that's a big improvement over the mopar carbs it will bolt on the mopar manifold /air cleaner would be needed.( I tried to keep mine all mopar but the stock holley 360 and 383 /400 carb flowed very close to the same almost 80 cfm down from the gm type
 
15 CFM by the factory rating.
2-Barrels

273 ~ {1964 thru 1969}
Carter BBD {1.437" Throttle Plates x 1.063" Venturi}.......... 275 CFM Rating

318 ~ {1968 and up}
Carter BBD {1.437" Throttle Plates x 1.186 Venturi}............ 285 CFM Rating

360 ~ {1971}
Holley {1.563" Throttle Plates x 1.343 Venturi}................... 350 CFM Rating

383 ~ {1962 thru 1971}
Carter BBD {1.563" Throttle Plates x 1.313" Venturi}.......... 365 CFM Rating

400 ~ {1972}
Carter BBD {1.563" Throttle Plates x 1.313" Venturi}......... 365 CFM Rating
 
But, FWIW, Holley and Carter used different vacuum amounts during the rating process. All being equal, I'm going with Rusty's response of "splitting hairs".
 
The Carter BBD is a much better, more reliable carb then the Holley. I've had a few 360 and 400 motors with the Holley 2-bbl and had nothing but problems with them. Replaced them with a Holley 1850 4-bbl and got more power and better fuel mileage. Had have a few motors with the Carter BBD and they ran forever.
 
We don't rate or judge a carburetor by how it runs out of the box. Thats a user issue..
After the few tid bits ive read ill comment that the roachaser carb is fat like most of the gm stuff. Chevys don't have much Rod ratio they initially pull harder on the intake port , of which are usually bigger than a chrysler intake port from the get-go....plus exhaust port is over efficient in most cases and fuel just goes out the tail pipe...GM was the 1st to have smog pumps.....dirty sob's they are...Chrysler longer rods, higher ratio, taller/narrow higher velocity intake ports..last to have a smog pump when they were used for a min...
Effeciencey durives from many things...flat out ...better engineering.
 
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Don't lose sight of the difference in ratings.
If you take a 300cfm rated 2bbl and put it on a HO engine,then; that 300 could be a 300/.667=450cfm. Add 2 more same-sized barrels and it could be a 550 using the 4bbl rating system.
Ever wonder why the 4bbl engines only made something like 35 hp more than the exact same engine with a 2bbl? Or why a 2x4 doesn't double your power? Or why a 4bbl on a stock smogger-teen with 2.76s won't fly?
The engine pulls what it will pull; if a 2bbl meets its needs, 8 barrels won't make it any more powerful.
A 360cfm 2bbl on a stock 360 cuber, only starts becoming an issue after 3450 rpm, but will pull fine to 4500, just about when the stock 360 starts to float the valves. You can put a 4bbl on it, and it sounds like a race engine, but it ain't gonna run thru first gear much quicker. And it's still gonna puke when the valves float. Jus saying.
 
yeah but if you make the 4 brl small enough..it will out run the 2brl and get a better mpg by means of smaller high velocity venturis aka holes- dont convieniently forget the thermoquad now..
Its an air speed vac signal tweek to mix the fuel better...smaller hole, faster moving air...but thats coming from a different angle than say.. 'mathmaticaly' what a cid needs to turn x rpm or make x hp.
If you turned a 318 high enough, stock cam with springs that can handle it... it will eat 850 dbl pump...to a point... Once the engine cant pump anymore cfm or turn anymore rpm yeah it will slow down when opening the throttle beyond that point and not go faster till you let off...then it will carry again...fuel dropping out of air*
The main thing or issue with the generalization of a STOCK 318 with a big 4 brl thrown on... is when all 4 open from a stand still...the air speed and vac aka signal..disappears...and its a really slow recovery, poor atomization...and more so as the carb venturis get bigger...in that example...however, same setup and now stall it @3500 or and watch it come to life and pull over that 2 brl at the top...for a couple more thou and fall off flat of course ...cause ultimately it needs valve timing to work at those rpms and be effecient.
...point, its all relative to what operational enviroment you're in...and 'transition' .
Id take a 390/500cfm 4 brl over a 300cfm carter bbd or even 500cfm holley 2brl, any day. And then there is this... the buick guys , you know...small runner...BIG CAM...huge carb. talking about small runner velocity pulling hard ...enough to run a 850-1050 carb.

its all relative to what animal and its environment we're talking about...and even the monkey holding the wrench.

had to edit the **** outta that, too many points getting crossed.
 
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All I know is that using the same truck, pulling the same load up the same mountains, was a noticeable difference in power with the 1850. Also when filling up on the other side of the mountains. Tried this with 4 different trucks with the same results.
Also here nothing works "out of the box". Just in my county the elevation goes from 4300 ft. to almost 11,000 ft. Jetting is always required.
The Holley 500cfm 2-bbl is a great carb.
Some good info though guys. :thumbsup:
 
Rainy Day Auto said:
Soooo is there much difference in flow between a 2 barrel carb from a 360 and a 2 barrel from a 383??

I have a 2 barrel from 72 360 and a 2 barrel carb from a 68 383.

Is there much if any difference??
Click to expand...

Have a look at the rods and jets between the two. numbers on the side. If they are the same flow rating...the jet/rod combo would be the difference. You can adjust the plastic arm inside to put the tapered rods lower, leaner, into the jets. iirr.
I used to play with those as a teenager on my slant. Once i figured out carburetors a little later.. i realized what i could have had...really knowing what to have changed/adjusted.
 
IMHO, if you don't care for fuel mileage, a two barrel that will satisfy the airflow needs of the engine is just as good as double pumper. Right now, .030 over 10:1 318 static timed to 14 and 34 total degrees mechanical all in at 2200 rpm with a sealed power CS109R cam installed straight up, with a 318 BBD on the factory single plane, pulls a lot more air than the stock 285 cfm rating. Enough so that I am setting the manifold up for a 383/400 BBD because there is enough vacuum at full throttle that it is adding vacuum advance.
 
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