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Help Please! Knocking Noise


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I win the biggest idiot contest this week. 

I have a 73 02 auto with a weber 32 36 with the water choke. I rebuilt it this weekend with a pierce manifolds kit and a new diaphragm from carbs unlimited and after reinstalling it took it for a spin. it ran great but after about 10 mins a loud knock started and after inspecting my rebuilt carb. there is a screw missing from one of the choke butterfly.


Can you please tell me where to begin looking for this thing? Do i need to just pull the valve cover or can this thing worked it way someplace else?


Other than a pertronix install, the carburetor rebuild was the first mechanical project on this car that I've done. 


Apologies for the bonehead move and thank you for your help and patience.



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Lesson learned here, folks:  if you remove a carb screw during a rebuild that can fall down the carb throat, either loctite it when replacing, or peen/centerpunch the threaded end so it won't come out.  The factory does this on Solexes for sure, and I think Weber does also, so if you remove any of these screws you'll have to re-peen them when reinstalling.  Truth be told, you normally don't need to remove either the choke or throttle plates unless you're rebushing the throttle shaft.


If you can determine which cylinder swallowed the screw (probably #2 or 3 as the passage is shorter), you might be able to rig up a small diameter rubber hose taped to a vacuum cleaner hose and with the intake valve open and the intake manifold off, either suck the screw up the hose or at least wedge it in the end of the hose and extract it.  But then you'd have to take on faith there wasn't any serious damage either to the head or the piston.   My '02 ran for many thousands of miles with what looks like a piece of spark plug porcelain embedded in a piston top--no problems at all.


Good luck



'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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Its a pretty complicated job. I strongly suggest you find a Haynes or similar manual, and follow the instructions closely. You best have head checked for straightness (assuming it is salvageable) and if you get it milled, be sure to attach the front cover plate. You will also need some special tools.

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