I've been working on trying to set the choke and tune my Motorcraft 2150 2V carb for quite some time now. Have searched for answers and tried several different techniques but it still doesn't seem to want to work correctly. Can't seem to get the thermostatic choke, vacuum solenoid, and fast idle set.


I can get it to start and run but the butterfly valve doesn't want to move open after the engine is warm. Should be just about closed when cold, right? Then open up as the engine warms? Should also close down some when I press the gas pedal to prime the carb right? None of that is working.


All of the linkages seem to be very loose, (ie too much play) could this be the problem?


Second issue is exhaust leak through the intake manifold(example pic below). Seems to be coming from where the coil had been mounted and it appears there may be a broken bolt/stud in the hole which will require me to remove the intake manifold in order to remove it.


That being the case, I'm wondering if I should just get a new carb. My neighbor (who is a car guy with several restorations finished and/or ongoing) seems to think I should put a new intake and a 4 bbl carb, something like a 650 cfm, on there since I'll have the intake off anyway. I'm not looking for any more power, just reliability and if possible, fuel efficiency, or at least not lower my fuel efficiency with new carb.


What would you do?


Truck is 78 F150 2wd with a 6.6L 400CID.



Arrow where exhaust is coming out. This is not the intake on my truck, just using for reference.

 

With a 400, I don't think your exhaust leak is the threaded hole for mounting the coil. Just below that on the front of the head is a small core plug. This plugs the passage that is used for air injection into the exhaust (air pump). These corrode and start to leak exhaust. Replace it and the leak will go away.
The MC 2100/2150 carbs are just about "dirt" simple but if the linkage is worn, and you're just going for reliability, I would just swap it for a rebuilt.
Here's a picture I stole from Heliguy's build thread showing a corroded plug.

 

Mike - is there a part number or source for that plug? Is it threaded? Would something from the hardware store fit?

/hijack

 

I appreciate the response and I'll check that location too, however, I know 100% there is exhaust coming from the location in the picture. Whether it's the threaded port where the coil mounts or not, I'm not certain, but there is definitely exhaust coming from it. That being the case, could it just be a place where a freeze plug should be cause there is nothing there now.


And as for my carb being "dirt" simple, I've heard that before trying to read up on it, but you'll have to forgive me as I am "dirt dumb" when it comes to this automotive stuff. This is my first project and I have zero experience working on motors besides changing the oil, so I'm learning as I go, or faking it anyway.

 

A long time ago I posted up a thread with a full 2100/2150 carb rebuild manual.

I believe the thread/links in it still work... EDIT: Checked it, looks like it still works. Surprising, since it's from 2010.

https://www.ford-trucks.com/forums/9...ce-manual.html

 

They're pressed in. Basically they're miniature freeze plugs. I think they're 7/16" diameter. I'll see if I can get a definite answer.

 

Well, I was off by 1/16". They're ½" diameter.
Plug, thermactor hole in head, ½" diameter
376301-S
Green Sales, Cincinnati, OH has 401 of them (800) 543-4959
There are also 41 Ford dealers that have them in stock.

 

I'm at a loss as to how it could be leaking exhaust from the coil mounting bolt. There's only one place on the intake where there is exhaust flow, that's the exhaust cross-over passage under the carburetor. Look at the picture you posted, see the small passage that's between the #2 & #3 and #6 & #7 ports? That's the exhaust cross-over. Its function is to route hot exhaust under the carburetor to assist fuel evaporation when the engine is cold. On some engines it also helps warm the automatic choke to open it up.
That's the only place where there is exhaust flow through the intake, like I say, it's puzzling.
Not being there in person, I'm still betting on the thermactor plug leaking.

And, as for you saying you're "dirt dumb". Don't beat yourself up! No one is born knowing this stuff. All of us, whether we'll admit it or not, was at that point sometime in our life. It's a learning curve. Compared to today's modern cars, these trucks are as simple as it gets, but if you've never worked on them, they may as well be just as complex. Knowledge is power, to borrow a well worn phrase, learn as much as you can. There is no better teacher than jumping in and start working, arm yourself with the manuals and parts catalogs. If you run into a problem, do just what you've done, post a question here. If you make a mistake, don't dwell on it. Back up, fix it, learn from it and move on.
These trucks can be a lot of fun if you let them.

 

I believe it is an exhaust port from the head. When you put your finger over the hole, it feels like you put your hand on the exhaust pipe, it'll push your finger off. Not 100% if this is the intended coil mounting location, it's an assumtion based on what the coil mounting bracket looks like, what the hole loccation looks like (mating surface with same angled edge), the size of the hole in each, the length of the wire on the coil can pretty much only be mounted there, and no other obvious mounting locations noted. I looked to take a picture of it yesterday, but there are about 50 different things in the way, wires, vacuum hoses, etc. One way or the other, my intake manifold will have to come off, which in the interest of learning, will be a new one for me so I'm actually looking forward to it.


So if it is a thermactor plug, it just presses in? Do I need some kind of sealant or adhesive?


Again, I appreciate you taking the time to provide your input.

 

Thanks, Mike. Much appreciated.

 

Update: I think I may have made some progress on the choke setup, or at least a step in the right direction. Was playing with the fast idle solenoid and fast idle cam and seem to have it starting and the butterfly valve does open now when the engine is warm. Stays open until cool and when I hit the gas pedal it closes.


Still seems as though it doesn't want to kick down out of fast idle once the engine is warm even after goosing the throttle, thinking the fast idle cam could use a little tweeking to fix that? Don't have a tachometer, but my neighbor has something that should allow us to set the idle rpm range appropriately, that is IF I can get the choke working correctly.

 

Yes, it just presses in. It's like a miniature freeze plug, only in this case you don't need any sealant.

 

Hey guys!

Quest, as far as you intake, I have the same one and mine has what seems to be a stud threaded into it. Not sure thougt if that hole taps into the exhaust cross over.

Like Mike posted, I searched and searched for an exhaust leak and couldn't find it. I thought it was coming out of the front of the exhaust manifold but found it coming out of the plug in the front of the head just behind the alternator as pictured above. I couldn't get the plug out so I used a 1/2 drill but and gently drilled it out. Went to NAPA and got a 1/2 inch outer diameter freeze plug and tapped it in using a small socket - no sealant. Now, no more gas leak.

 

So that stud is missing on mine and it appears a portion of it is still in the hole, but that IS where exhaust is coming out. One way or the other, it looks like my intake manifold will have to come off. I'll try to remember to take some pictures of both sides of the intake and the top of the head where the stud connects, if/when I get the intake off.

 

I was reading another thread this morning that was talking about the 400. It mentioned that there are also thermactor passages in the head at the corners of the intake manifold. If that's correct, it sounds like that might be your problem.
Here's a link to that post:
https://www.ford-trucks.com/forums/1...l#post16659217