Carburetor swap
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Carburetor swap
I have a 1973 f-100 with a 302, and a motorcraft 2100 carb. I'm thinking of swapping to an edelbrock 1405 and I'm not sure what intake. I don't race it or anything, I mainly want better gas mileage but I don't want to sacrifice much performance. I just wanted to know what you guys thought before I started spending money
Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
What mileage are you getting now? The 2100 is one of the best carburetors ever made, bar none. 4 bbl carbs can get better mileage than a 2 bbl, but that's not the way to bet because ya hafta keep yer foot off the pedal.
2100s came in a bunch of different venturi sizes and clusters. After all this time there's no telling what's on there. They range from 1.02" to 1.21", if you look on the side of the airhorn there will be an embossed clock looking deal with the venturi size. Probably 1.08" or 1.12", Ford was pretty good about sizing carburetors. A smaller carb will idle better and run smoother with more low end torque. A big carburetor will really only show any benefit at wide open throttle at the top end. How much of your driving is at WOT? I had a 500 CFM Holley on the Y block and replaced it with the stock 1.02" carb it came with. It runs better than it ever did, performance wise, and fuel mileage about tripled. Big carbs are a classic mistake, the engine is just an air pump. If it can't utilize the extra CFM and fuel it will be wasted $$ and it won't run very well, and get ****ty mileage to boot.
2100s came in a bunch of different venturi sizes and clusters. After all this time there's no telling what's on there. They range from 1.02" to 1.21", if you look on the side of the airhorn there will be an embossed clock looking deal with the venturi size. Probably 1.08" or 1.12", Ford was pretty good about sizing carburetors. A smaller carb will idle better and run smoother with more low end torque. A big carburetor will really only show any benefit at wide open throttle at the top end. How much of your driving is at WOT? I had a 500 CFM Holley on the Y block and replaced it with the stock 1.02" carb it came with. It runs better than it ever did, performance wise, and fuel mileage about tripled. Big carbs are a classic mistake, the engine is just an air pump. If it can't utilize the extra CFM and fuel it will be wasted $$ and it won't run very well, and get ****ty mileage to boot.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
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From: NorCal
I had a 76 F150 LB with a 2V 302, auto trans, and 3.00 rear gears. It could get 17 to 18 MPG on the highway when driven conservatively at 60 mph.
Swapping to a 4V may or may not result in better MPG. The drivetrain should be thought of as a system... what is your rear gear ratio?
Swapping to a 4V may or may not result in better MPG. The drivetrain should be thought of as a system... what is your rear gear ratio?
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Senior User
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What mileage are you getting now? The 2100 is one of the best carburetors ever made, bar none. 4 bbl carbs can get better mileage than a 2 bbl, but that's not the way to bet because ya hafta keep yer foot off the pedal.
2100s came in a bunch of different venturi sizes and clusters. After all this time there's no telling what's on there. They range from 1.02" to 1.21", if you look on the side of the airhorn there will be an embossed clock looking deal with the venturi size. Probably 1.08" or 1.12", Ford was pretty good about sizing carburetors. A smaller carb will idle better and run smoother with more low end torque. A big carburetor will really only show any benefit at wide open throttle at the top end. How much of your driving is at WOT? I had a 500 CFM Holley on the Y block and replaced it with the stock 1.02" carb it came with. It runs better than it ever did, performance wise, and fuel mileage about tripled. Big carbs are a classic mistake, the engine is just an air pump. If it can't utilize the extra CFM and fuel it will be wasted $$ and it won't run very well, and get ****ty mileage to boot.
2100s came in a bunch of different venturi sizes and clusters. After all this time there's no telling what's on there. They range from 1.02" to 1.21", if you look on the side of the airhorn there will be an embossed clock looking deal with the venturi size. Probably 1.08" or 1.12", Ford was pretty good about sizing carburetors. A smaller carb will idle better and run smoother with more low end torque. A big carburetor will really only show any benefit at wide open throttle at the top end. How much of your driving is at WOT? I had a 500 CFM Holley on the Y block and replaced it with the stock 1.02" carb it came with. It runs better than it ever did, performance wise, and fuel mileage about tripled. Big carbs are a classic mistake, the engine is just an air pump. If it can't utilize the extra CFM and fuel it will be wasted $$ and it won't run very well, and get ****ty mileage to boot.
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I had a 76 F150 LB with a 2V 302, auto trans, and 3.00 rear gears. It could get 17 to 18 MPG on the highway when driven conservatively at 60 mph.
Swapping to a 4V may or may not result in better MPG. The drivetrain should be thought of as a system... what is your rear gear ratio?
Swapping to a 4V may or may not result in better MPG. The drivetrain should be thought of as a system... what is your rear gear ratio?
18 mpg in a dent! Wow!
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
Upgrade the exhaust before upgrading the intake side of the engine.
You're asking a long distance runner to breathe through a straw... it's easier to breathe with a big straw so uncork the power that is likely already there but restricted by crappy exhaust manifolds.
When I bought my 73 4x4 it was equipped with a 4v carb and intake but still wore the restrictive FE manifolds and 2.25-inch duals. The PO gave me the headers he never installed and I installed them along with 2.5-inch tubing as an upgrade..... It was evident to my butt dyno that there was definitely more power.
You're asking a long distance runner to breathe through a straw... it's easier to breathe with a big straw so uncork the power that is likely already there but restricted by crappy exhaust manifolds.
When I bought my 73 4x4 it was equipped with a 4v carb and intake but still wore the restrictive FE manifolds and 2.25-inch duals. The PO gave me the headers he never installed and I installed them along with 2.5-inch tubing as an upgrade..... It was evident to my butt dyno that there was definitely more power.
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Probably right, I do need to get rid of those manifolds. I dread taking them off though. Think I'll have to insulate the starter with short tubes? Have headers fried any spark plug wires?
I already have duals, I'm not sure on the diameter though, but from what I remeber they are mandrel bent
I already have duals, I'm not sure on the diameter though, but from what I remeber they are mandrel bent
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