Carb questions: 500 CFM 2 barrel on a 300
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Fleet Mechanic
Joined: Aug 2009
Posts: 1,771
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From: Western Washington
Carb questions: 500 CFM 2 barrel on a 300
How would that work out? As far as I'm concerned, the carb is almost perfect on a 390, but that 390 has 90 extra inches and 2 cylinders over a 300. How well would it work on a 300? The engine would be mostly stock, with EFI exhaust manifolds and maybe one of the Offy or Clifford intakes with a 2 barrel adapter on top.
Sam
Sam
Tuned
Joined: Nov 2007
Posts: 386
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From: Whitmore lake Mi
That was always my dream. I think it would feel good on the throttle but bad an the wallet. I think fuel eco would be better with a sm 4 barrel. I did put one on a stock 351W in a Torino once and it made it run well. I don't remember the mileage difference that was back when it did not matter so much. I have a couple laying around in my piles of "stuff". I will not be using them as I am going with 3 x 2 weber style TBI.
Jim
Jim
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Fleet Mechanic
Joined: Aug 2009
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From: Western Washington
So my gas milage would probably still be 10 MPG? That might be a deal breaker, because that's the same milage I get with the 390. If I got 12, or 13 with the 300 it'd be worth the work.
Sam
Sam
Postmaster
Joined: Dec 2006
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From: Spokane, WA
Fair = 2V adapter with the intake manifold opening enlarged oblong as much as it can stand.
Better = Intake manifold modified and a 2V mounting plate installed...a machine shop operation. (SB6 owners have done this quite a bit.)
Best = Clifford or Offy C manifold with a 2V adapter plate.
The conditions impacting MPG are so numerous that there is no way to project what MPG will be.
Better = Intake manifold modified and a 2V mounting plate installed...a machine shop operation. (SB6 owners have done this quite a bit.)
Best = Clifford or Offy C manifold with a 2V adapter plate.
The conditions impacting MPG are so numerous that there is no way to project what MPG will be.
Thread Starter
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Fleet Mechanic
Joined: Aug 2009
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From: Western Washington
Yeah, I understand, the MPG is a tough one to forecast. The truck is a 2wd 73 f250, np435 4 spd, 4.10 rear (DANA 60) regular cab, long bed. Not exactly the best setup for good gas milage! 
So for me, if I were to swap in a 300 (with the holley 2bbl) and gain 2 MPG, it would be worth it, but if the 300 would only get 10, I'd keep the 390 and re-build it. I love the 300, but unless it would get a bit better milage, the 390 would be a better choice.
Sam
So for me, if I were to swap in a 300 (with the holley 2bbl) and gain 2 MPG, it would be worth it, but if the 300 would only get 10, I'd keep the 390 and re-build it. I love the 300, but unless it would get a bit better milage, the 390 would be a better choice.Sam
Posting Guru
Joined: May 2007
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From: North Reading Mass
The Ford 2100 series have some venturis that flow around 350-390 CFM IIRC. This carb got me about 18 mpg at 60 mph in a 4x2 83 F150 302/AOD 3.55s Average was 16. I did switch to a 500 Cfm 2100 from a 351 and the mileage dropped to 14. The WOT performance was better but low speed drivability suffered. I then switched to a Quadrajet off of a 305 which was the best of both worlds.
regards
rikard
regards
rikard
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