2150 weird question
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Postmaster
Joined: Jun 2003
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From: WA
2150 weird question
I bet Bubba knows this answer.
A couple years back( and before I cared about learning about engines), I had to replace the 2150 on my 79F150/351M. The tag on the existing carb on it said it came off a '76 car. I got a rebuilt carb that matched the '79 truck. I was having trouble getting through emissions along with problems with the accel pump, floats sticking and stripped screws so a replacement seemed warranted. The shop that put it on (if I remember all this correctly) said they took the jets out of my old carb and re-used them, but they were smaller and they had to solder closed some orifice and then drill it out to make the opening smaller. What on earth orifice would they have done this too? I no longer have to get emissions tested, and wanted to open this carb for power.
A couple years back( and before I cared about learning about engines), I had to replace the 2150 on my 79F150/351M. The tag on the existing carb on it said it came off a '76 car. I got a rebuilt carb that matched the '79 truck. I was having trouble getting through emissions along with problems with the accel pump, floats sticking and stripped screws so a replacement seemed warranted. The shop that put it on (if I remember all this correctly) said they took the jets out of my old carb and re-used them, but they were smaller and they had to solder closed some orifice and then drill it out to make the opening smaller. What on earth orifice would they have done this too? I no longer have to get emissions tested, and wanted to open this carb for power.
Posting Guru
Joined: Aug 2000
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From: (near) Denver USA
2150 weird question
There are two kinds of calibrated orifices, fuel metering orifices (which jets are) and air bleeds.
Reducing the size of a fuel metering orifice will make the fuel/air mixture leaner. Reducing the size of an air bleed orifice will make the mixture richer.
Frankly, I'm stumped as to what they did. I think it's weird that they didn't just use the new truck carb, which should have had the correct calibration right out of the box.
You could try taking the carb apart and examining the orifices for evidence of modification (i.e., solder residue).
Reducing the size of a fuel metering orifice will make the fuel/air mixture leaner. Reducing the size of an air bleed orifice will make the mixture richer.
Frankly, I'm stumped as to what they did. I think it's weird that they didn't just use the new truck carb, which should have had the correct calibration right out of the box.
You could try taking the carb apart and examining the orifices for evidence of modification (i.e., solder residue).
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Postmaster
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From: WA
2150 weird question
Would I be correct in assuming that when I clean out whatever they did I will need to start playing with jetting to get it running right again? I'm tempted to just try and find the higher flow 2150 from a junkyard and rebuild it , mines a 1.21
P.S. love your website bubba!
P.S. love your website bubba!
Senior User
Joined: Jun 2003
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From: Harlan, KY
2150 weird question
Fuel metering jets may not have a straight hole. They sometimes have a conical shape which is difficult to form. If you try to remove the solder, try not to remove any of the brass. Finding an assortment of jets to work with is a way to go. Shops may have them and junkyard carbs are a source. A trashed carb may not be rebuildable, but often will have useable parts. I was able to build a working carb for a 63 Olds Cutlass from several trash carbs.
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From: (near) Denver USA
2150 weird question
I wouldn't recommend just cleaning out whatever they did. Find out what they did first, then decide. You might not need to change it, or you might need to seal off the orifice completely.
The 1.21" carb will give you plenty of flow for a 351M, unless the engine is severely modified. You can improve the 2150's flow capacity about 10% by just polishing the upper end of the air path and cleaning the casting flash off the down legs and the outside of the booster venturi barrels.
Jets on the Morotcraft 2150 have just straight, drilled holes. Even if you made a "conical" hole in the jet, the smallest diameter of that hole would determine the orifice size, so it would act no differently than a straight hole of that diameter.
The 1.21" carb will give you plenty of flow for a 351M, unless the engine is severely modified. You can improve the 2150's flow capacity about 10% by just polishing the upper end of the air path and cleaning the casting flash off the down legs and the outside of the booster venturi barrels.
Jets on the Morotcraft 2150 have just straight, drilled holes. Even if you made a "conical" hole in the jet, the smallest diameter of that hole would determine the orifice size, so it would act no differently than a straight hole of that diameter.
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