'66 273 BBD Carb

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SpiderHelix

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Hello:

I broke one air mixture screw off in the carb when trying to remove it. Half of the screw is still in the carb throttle plate. Apparently, the mixture screws are not meant to be removed.

There are threaded holes that angle down toward the screw, maybe holding the air screw in?

There doesn't seem to be a way to remove whatever is in the angled holes though, either.
This is an original California carb, which may be why the screws can't be removed.

Any advice, short of "new carb?" :(
Thx

Base-plate.jpg
 
Yep, you screwed the pooch!

I believe the screw in the hole is a Allen screw.

Get that out then you MIGHT be able to with a left hand drill unscrew the mixture screw.

I had the same issue with a CAP 67 Carter 4 bbl. ( I bought it that way)

The other issue you might run into is finding a replacement screw

good luck
 
Sorry for my ignorance on this but what are those holes for? Idle mixture screws look intact. Is it just a bleed hole? Or a clean out hole plugged from manufacture passage drilling? If so - any good tig welder could weld that up in a flash for you. A dab of weld and flush it off and done. Again- not knowing what it is for as in 40 years of rebuilding carbs I’ve yet to see that. good luck and let us know how you make out.
 
It's damn tough to get those small screws out. Is it steel or brass? Just asking in case someone is damn handy with a tig welder. It might be easier to start a wanted thread and find a used carb. There might be a few around yet from guys that took their 2 barrels off for a 4 barrel. I see a rebuilt or two available as well. More Information for AUTOLINE C679
 
Syleng1 said:
Sorry for my ignorance on this but what are those holes for? Idle mixture screws look intact. Is it just a bleed hole? Or a clean out hole plugged from manufacture passage drilling? If so - any good tig welder could weld that up in a flash for you. A dab of weld and flush it off and done. Again- not knowing what it is for as in 40 years of rebuilding carbs I’ve yet to see that. good luck and let us know how you make out.
Click to expand...

One idle mixture screw is intact, the other is broken off (the large hole). The small angled holes I have never seen before either. I think it is because it is a damn emissions carb so you can't get the air screws out completely. It looks like there may be plugs in the small holes, and possibly an allen head under that. Not tried to get the plugs out yet.
 
toolmanmike said:
It's damn tough to get those small screws out. Is it steel or brass? Just asking in case someone is damn handy with a tig welder. It might be easier to start a wanted thread and find a used carb. There might be a few around yet from guys that took their 2 barrels off for a 4 barrel. I see a rebuilt or two available as well. More Information for AUTOLINE C679
Click to expand...

I don't know what welding would do for me. I may try and drill out the small screws, then plug the holes with silicone. There is a local guy with a rusty carb, but it looks like the air screws are okay on it.

Thanks for the link. The one for my application is available, too.
 
SpiderHelix said:
I don't know what welding would do for me. I may try and drill out the small screws, then plug the holes with silicone. There is a local guy with a rusty carb, but it looks like the air screws are okay on it.

Thanks for the link. The one for my application is available, too.
Click to expand...
I re read your original post. Did you break off a mixture screw? (with the spring on it)
 
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The small screws are there to limit the amount of turns the idle screws can be turned out.

The mixture screws have a waist on them, think 36 24 36 and the small screw intersects the mixture screw at the 24 part.

upload_2018-3-28_9-26-30.png


[Found!] - Carter Idle Adjuster Screw (for CAP Carb)
It was a CAP thing to prevent tampering by the owner.

Had I used a left had drill bit / easy out I probably could have gotten the broken part out

I tried drilling it out but got off center and ended up screwing it all the way in and out of the threads in it's hole. Hence the need to drill out the lead plug.

The 2bbl is different in this location so it might be easier.
20180326_202626.jpg


As for welding I think the thought there is weld a rod to the broken part in the carb and use it to unscrew the broken bit.

This is from the 4bbl but you can see the set screw sticking out. I was able to drill out a lead plug ( lower hole) to get the broken part out.
20180326_202758.jpg

20180326_202737.jpg
 
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Dana67Dart said:
The small screws are there to limit the amount of turns the idle screws can be turned out.

The mixture screws have a waist on them, think 36 24 36 and the small screw intersects the mixture screw at the 24 part.

View attachment 1715761810

[Found!] - Carter Idle Adjuster Screw (for CAP Carb)
It was a CAP thing to prevent tampering by the owner.

As for welding I think the thought there is weld a rod to the broken part in the carb and use it to unscrew the broken bit.

This is from the 4bbl but you can see the set screw sticking out. I was able to drill out a lead plug ( lower hole) to get the broken part out.View attachment 1715761798
Click to expand...

Very helpful - thank you! Totally explains the set screws.
I have to get the air screws out first to see what I have. I do have a Thermoquad here I may be able to rob from.
 
Dana67Dart said:
The small screws are there to limit the amount of turns the idle screws can be turned out.

The mixture screws have a waist on them, think 36 24 36 and the small screw intersects the mixture screw at the 24 part.
[Found!] - Carter Idle Adjuster Screw (for CAP Carb)
It was a CAP thing to prevent tampering by the owner.

As for welding I think the thought there is weld a rod to the broken part in the carb and use it to unscrew the broken bit.

This is from the 4bbl but you can see the set screw sticking out. I was able to drill out a lead plug ( lower hole) to get the broken part out.View attachment 1715761798
Click to expand...
Dana67Dart said:
The small screws are there to limit the amount of turns the idle screws can be turned out.

The mixture screws have a waist on them, think 36 24 36 and the small screw intersects the mixture screw at the 24 part.

View attachment 1715761810

[Found!] - Carter Idle Adjuster Screw (for CAP Carb)
It was a CAP thing to prevent tampering by the owner.

Had I used a left had drill bit / easy out I probably could have gotten the broken part out

I tried drilling it out but got off center and ended up screwing it all the way in and out of the threads in it's hole. Hence the need to drill out the lead plug.

The 2bbl is different in this location so it might be easier.
View attachment 1715761813

As for welding I think the thought there is weld a rod to the broken part in the carb and use it to unscrew the broken bit.

This is from the 4bbl but you can see the set screw sticking out. I was able to drill out a lead plug ( lower hole) to get the broken part out.View attachment 1715761798
View attachment 1715761812
Click to expand...
Thanks for that info. I remember running into those screws before and never knew why they were that way. I learned something new today.
 
Ford used a plactic cap that snapped on the outside of the screw to prevent more than a few degrees of rotation.

Easy to remove.

I think I even saw a screw like on the bbd on a motorcraft 2 or 4 bbl at one point
 
Dana67Dart said:
Ford used a plactic cap that snapped on the outside of the screw to prevent more than a few degrees of rotation.

Easy to remove.

I think I even saw a screw like on the bbd on a motorcraft 2 or 4 bbl at one point
Click to expand...

Even my lawnmower has a plastic cap. :)
Covers are common on motorcycles. A sheet metal screw pops them right out.

I may punt on this and use this as an opportunity to get a 4 bbl. I love the original 66 small-bore air cleaner though.
 
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