Mystery Hole in my 2150

[Bulletproof250]

I think I found my last Vacuum leak. Under the top plate on my Motorcraft (2150?) and goes all the way through to the bottom plate of the carb (mounting surface)

 NOTE:Double-click on images for Full size/complete images

What does this hole do, other than provide me a significant Vacuum leak?

  

The gasket I have doesn't cover it, but even if it did what does it do? Can I just cover it, or Plug it?
  

I'm on my way to tuning th idle mixture screws and seting the final timing, with a nice smooth idle.
 

[Gary Lewis]

I'm at a loss as to what that goes to.  But your second pic doesn't seem to show it.  However, it may be associated with the EGR system.

In any event, I'd put a piece of aluminum duct tape over it for a test and see how things go.  I doubt the tape will hold very long, but long enough for a test.

[Bulletproof250]

I feel like I stumped and expert! Hahaha

I think the images require a double-click to see the hole and its relation to the gasket. The more confusing part is the "bead" impression from the top plate does not complete the seal. I looked though to other gaskets I have left over from past rebuilds, and those wouldn't make any improvement.

Thanks again for the quick response, and I'll plug it while I tune in the idle.mix and see what happens. I see and opportunity for tapping the hole for Set-screw if the tape works

[Gary Lewis]

I'm certainly not an expert.  I've tagged Bill/85lebaront2, who is one of those, and maybe he will know.

But, after double-clicking the 2nd pic I see what you mean.  I can see the hole and assume from what you've said that it goes straight through.  And I see what you mean about it maybe not making a complete seal with the cover.  But I suspect that it does.

The real question is if there is a passage in the cover that allows air in.  Have you checked that out?  I check out passages by squirting compressed air through them and finding where it comes out.  (I used to use carb or brake cleaner but found out the hard way that many of the passages don't go anywhere and the cleaner comes right back in your face - and BURNS!)

[Bulletproof250]

Additional information:

I currently have minimal concern about the Choke operation although I did find some information form


Credit to :Motorcraft 2100 Jeep AMC - street2mud.com

  

 and on my Actual Carb Gasket Surface NOTE: the "Non Sealed Area" on the right and it's relation to the surface on the far left

  

[85lebaront2]

From what you seem to be describing, it appears that the bowl gasket is the wrong one, Ford made a number of running changes in these carburetors, from the original 2100 in 1957, into the 2150 around 1975 to improve emission characteristics without sacrificing driveability. Unfortunately the balancing act between the two, failed on the 351m and 400. they were so lean as to barely run and got poor fuel economy.

If you bought the carburetor from a rebuilder, I would ask for a warranty replacement. If you just opened it up and found these issues, maybe a good (not Tomco) rebuild kit might solve any problems.

[Gary Lewis]

Thanks, Bill.  

[Bulletproof250]

Thank you Bill

This was on the truck when I got it. I've put "a" rebuild kit in it, but I cannot guarantee that it is a "good" one. If is just a gasket to seal off this hole I would assume that a permeant plug, would be an acceptable option since getting the correct gasket is probably not that accessible (today) haha.

 Bill or Gary  

do you see any reason that would be detrimental to the longevity of the motor, why I should not do this?

[Gary Lewis]

I would check the lid to see if that hole goes anywhere.  There are many holes in carbs but not all of them were drilled out for a given application.  So if the lid seals that one then you don't need to do anything more.

If the hole is drilled in the lid and there is a path for air through there then I'd try plugging it.  But I wouldn't do it in a permanent way.  I'd be tempted to put the piece of tape on it I mentioned for trial.

As for hurting the engine, you won't because taking air out of the air/fuel mix enrichens it and you won't hurt the engine going rich.

[85lebaront2]

If it is leaking vacuum there, then plug it, if not, leave it alone. Ford went from a piston choke break, to an air horn diaphragm (the slot was it's vacuum passage) to an external diaphragm, which is what yours has.

As I said, if there is no vacuum on it, don't worry. Ford like most makes a basic casting and some holes are never drilled through, just the pilot in the casting remains. If it goes to the outside air, bit it's mating portion is not there or not completed, ignore it.

That gasket in the first picture is either (a) from a very cheap kit or (b) poorly made or (c) has been modified.

[Bulletproof250]

Perfect answers, and information, Bill and Gary Thanks again!

I'll try and remember to post my creativity in an update