Dellorto 40 DHLA H Idle Mixture Screw Question - Alfa Romeo Bulletin Board & Forums

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Old 05-04-2006, 07:38 AM
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Dellorto 40 DHLA H Idle Mixture Screw Question

I got a set of DHLA 40 H's with other parts when I bought my 74 GTV and I decided to clean them up while cleaning up a set of Weber DCOEs. I stripped them, cleaned them up and installed new gaskets and O rings. When it came to putting the Idle Mixture Screws back in the front carb, the Screw would not hold in the seat of the #1 throat. It seems someone along the way may have stripped out the threads in the seat. Actually, it seems as if the threads may have just worn away to the point that the Idle Mixture screw threads will not engage enough to hold with the pressure of the spring and new O ring pushing the screw back out of the seat. I should have figured that something was wrong when I took the carb apart as that Mixture screw was really just sitting in the seat and not screwed in much if at all.

Now to my question. Is the carb body now a throwaway or is there some fix that could be done like a threaded sleeve (i.e. like a helicoil deal) or maybe welding/soldering new metal in the hole and rethreading? The thread is very fine so finding a tap might be problematic. Could a Carb shop help me with something like this? I'm new to working with carbs so any help would be appreciated.

Also I posted a thread on the Parts For Sale/Wanted for a DHLA body if someone has one that is sitting on a shelf somewhere Link to Thread

Thanks
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Old 05-04-2006, 08:20 AM
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As far as the bodies go, you'd probably want to match up the body letter (you'll see it after the carb designation on the upper left side of the carb) as some are different. Apparently this is a known problem with the fine threads. One of my carbs had a float post repaired with what looks like gray epoxy. I guess potentially, a different screw could be used and the body retapped; the idle mixture screw is a pretty coarse adjustment; perhaps a Weber screw could be used which has a more coarse thread, but this is a guess.
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Old 05-04-2006, 08:40 AM
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Dan,

Thanks for the reply!!! That is a good point if I can't figure out a way to fix it then I would need a "H" body to match the other one I have. Also the one I would replace has what looks like a vacuum fitting on the front barrel. Not sure what that is all about yet.......still learning about Dellortos.

BTW don't you have patients to see
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Old 05-04-2006, 09:21 AM
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Carb body

My problem was just the opposite. I had a bent throttle shaft and a stuck idle screw. Had to have someone with a very small drill take it out.

My thinking is that there is some smog related connections if you have an extra port.
There was an extra screw just before the idle mixture screw that I had to sort through. Evidently from what I can deduce is that the extra screw was for a coarse fuel flow before the idle to help with emissions.
I have a spare body you can have for nothing if you want it. I don't think it is an H model. Contact me privately for more info. I will have to dig in to the spares boxes to find it and photograph it.
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Old 05-09-2006, 07:33 PM
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VeloceDoc,

Sent you a PM. Thanks

Mike
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