Need some help here. Hadn't needed to adjust carbs for too long - everything has been running just fine. Front idle adjusting screw twisted right off flush with the carb body!! So now what? How do I get the remaining screw out? Tried grabbing the less than 1/8" remaining below the flange with a needle nose vise grip and got it to move a little, but not enough space or purchase to screw it downards to remove it. I'm trying to solve this without dismantling and removing the carb from the manifold. Any ideas? Would drilling it out be stupid? How hard is this screw steel anyhow? Don't want to even come close to drilling out the threads in the carb body - I had these carbs rebushed,
I have spare replacement screw.

I had the same thing happen on HIF carbs on my 144.
Don't do what I did.

I tried to use a screw extractor on what was left of the broken screw.
Drilling the hole through the center of the screw was no problem and did not damage anything. But when twisting the screw extractor, I snapped off the corner of the tab into which the idle screw screws rendering it unuseable. I wasn't wailing on it, I guess due to it's age, it just didn't take much torque to snap it.

I now have to use the carb vent stop screw (HIF carbs) to set the idle on that rear carb.

Lesson learned; I should have just drilled and re-tapped the hole.
--
'60 544, '68 220S, '70 145S, '72 144E, '86 745T

As Kombi says, try to loosen it over time with penetrating oil. A bit of heat from a Bernzomatic torch will help too.
If you drill it out sucessfully, drill and tap for a 10-32 screw and use that for an idle screw. I have had to do this a few times to save rare SU bodies.

Just my .02, but don't do anything until you have soaked the 'stub' and the area in general with penetrating oil of some sort! then screw it UP! the break may/will have messed up the threads on the screw, and screwing it DOWN will transfer that to the carb body threads. at worst the screw can be drilled out and re-tapped on the car if done carefully...do not get in a hurry, it costs time IMHO!

Cheers!
Dave G.

P.S. use a transfer punch to center the drill in the steel remainder of the screw if you have to drill, the steel is soft, but not as soft as the carb body, you do not want the drill to 'wander'...start small (.062") and work up.

My approach would be to screw the stub up enough to file off any burr where the screw broke, and then to screw it down through the carb, due to the fact that grabbing the lower part of the remaining screw has chewed up the remaining threads. There's just not a lot of room to grab what's left, or much room to maneuver. I'd rather take my chances unscrewing the remains. Once I start drilling, if what's left breaks or collapses, then I have no choice except to drill and retap the hole. I need a better needle nose vise grip.

The other guys have great ideas but if you get to the point of drilling it out, go get yourself a set of left hand drills... These have the cutting flute going backwards to normal. Thus the drill is spinning counter clockwise when cutting. It can help back out the broken piece or if it grabs, it comes out rather than forces it in farther. You should be able to get a set of left hand drill bits at a decent machine tool supply store.

Danny,
Can't you cut a slot into the screw with a fine hacksaw blade? If you have 1/8" protruding, that should be enough to get a screwdriver into it.
Bob S.

Another good suggestion. The 1/8" that's left is below. The screw broke off flush on the top. Sure, if I removed the carb from the engine and had it on the bench I might be able to do this. I'm trying to do this with the carb in place on the engine.

Forum;

Nobody has mentioned the cause of this seized screw...Galvanic corrosion between dissimilar metals, exacerbated by the fact that this screw is not moved too often...so whatever method you use to remove the remains (and I would start by saturating the thing with the penetrating lube of your choice)...and you MAY wind up oversizing the replacement screw (it's not the end of the world and wouldn't be the first time...), I suggest you Anti-Seize the threads after your repair (and on the other carb too!) to keep this from happening again....the locking springs on the screws will see to it that the adjustment stays put.

...just another use for AS...they just don't learn until this happens!

Cheers

This is a great idea, except that in trying to loosen the remaining screw, I've sort of chewed up the threads. If I try and back the screw out through the body I think I'll be tearing up the threads in the carb. I'm just hoping to thread what remains down and out. I need a tiny pair of Knipex channel locks or a good pair of needle nose visegrips to grab what little is left.