2150 question?
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5th Wheeling
Joined: Aug 2018
Posts: 41
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2150 question?
Ive rebuilt the carburator 3 or 4 times now on my 77 F250 (400CI).
I think the poor thing is just plain worn out. Its rich, then lean, sometimes bogs out bad, about the only good thing about it is cold starts (5* this morning and it fired right up)
But my question is, i see tons of brand new (not rebullt) 2150s that say they are for 289-351ci motors, so im assuming they are the 1.03 venturi size. My 400 has the 1.21 venturi.
How much power would i lose going to the smaller carb? Is it a bad idea all the way around? The 400 carbs carry a rather hefty price tag over the other ones.
Input is apperciated.
I think the poor thing is just plain worn out. Its rich, then lean, sometimes bogs out bad, about the only good thing about it is cold starts (5* this morning and it fired right up)
But my question is, i see tons of brand new (not rebullt) 2150s that say they are for 289-351ci motors, so im assuming they are the 1.03 venturi size. My 400 has the 1.21 venturi.
How much power would i lose going to the smaller carb? Is it a bad idea all the way around? The 400 carbs carry a rather hefty price tag over the other ones.
Input is apperciated.
Logistics Pro
Joined: Jul 2005
Posts: 4,217
Likes: 154
Are you sure the choke is functioning correctly? If you're missing the choke hot air tube, (the brake line sized line from the choke housing to a blind hole in the manifold) or the larger hose which runs from the heat stove on the exhaust manifold to the air filter snorkel, the choke won't always stay open. There's also the wire from the alternator "S" post to the choke housing. I'm sure if it's missing, you'll get similar symptoms.
I'm almost positive you'd notice the smaller carb when driving. If you're lucky, you'll feel a tiny bit of extra torque down low, but you will likely lose top-end horsepower. You could always switch to a Holley...
I'm almost positive you'd notice the smaller carb when driving. If you're lucky, you'll feel a tiny bit of extra torque down low, but you will likely lose top-end horsepower. You could always switch to a Holley...
Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
The 1.21 can be found new, they are easy to distinguish as they cost more and they do not have the deep power valve cover. I have posted on the subject plenty. I believe I have used 10 or so and no issues, the rebuild kits are the same and the parts interchange. All of mine have been fine out of the box.
Click here
Click here
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Did they make a 1.03" size?
Have to ask yourself what you are using the truck for, and what do you want it to do. If you want to be able to kick *** and take names, you'll have to give it some juice. If you're just making runs to the yard waste site and Lowe's and cruising for an ice cream cone or whatever, you'll probably never notice the difference except at the top end, at high RPM. A 1.08" or 1.12" should work OK, but it would be anemic. A 1.21 should be a good choice for a street driven truck.
A lot of people are unrealistic about carburetor needs, they see a CFM calculator and plug in 6000 RPM at 100% efficiency and then select the next size up. Maybe that works for drag racing. But that doesn't mean a street driver wants to do that.
Try this: 75% or 80% efficiency (for stock heads) and then plug in your typical highway cruise RPM in high gear. That's how much carb it actually needs just for cruising basically. It will be very close to what the factory provided, at least for heavy trucks.
Read this: http://www.thecarburetorshop.com/Carburetorsizeselection.htm
It looks like say, the equivalent of the Holley 350 CFM would be about right, or 1.21" venturi.
Have to ask yourself what you are using the truck for, and what do you want it to do. If you want to be able to kick *** and take names, you'll have to give it some juice. If you're just making runs to the yard waste site and Lowe's and cruising for an ice cream cone or whatever, you'll probably never notice the difference except at the top end, at high RPM. A 1.08" or 1.12" should work OK, but it would be anemic. A 1.21 should be a good choice for a street driven truck.
A lot of people are unrealistic about carburetor needs, they see a CFM calculator and plug in 6000 RPM at 100% efficiency and then select the next size up. Maybe that works for drag racing. But that doesn't mean a street driver wants to do that.
Try this: 75% or 80% efficiency (for stock heads) and then plug in your typical highway cruise RPM in high gear. That's how much carb it actually needs just for cruising basically. It will be very close to what the factory provided, at least for heavy trucks.
Read this: http://www.thecarburetorshop.com/Carburetorsizeselection.htm
It looks like say, the equivalent of the Holley 350 CFM would be about right, or 1.21" venturi.
Thread Starter
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5th Wheeling
Joined: Aug 2018
Posts: 41
Likes: 0
The 1.21 can be found new, they are easy to distinguish as they cost more and they do not have the deep power valve cover. I have posted on the subject plenty. I believe I have used 10 or so and no issues, the rebuild kits are the same and the parts interchange. All of mine have been fine out of the box.
Click here
Click here
The one in that link has the small cover, so it should be a 1.21 right?
The truck is actually my daily driver and i use it for hauling/towing on occasion.
The choke seems to work right, the hot air tube has been replaced, but the big flexi pipe that comes up from from the manifold to the air cleaner isnot intact, but the choke seems to open and close properly.
I have thought about switching to a holley 500 2bbl, but dont wanna lose my auto choke. My truck does not have an electric choke, only hot air.
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