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carb synchro

1646 Views 2 Replies 2 Participants Last post by  alfaseb
Hello, I´ve had some trouble with my 82 alfetta gtv tuning up specially with setting the carbs. I am a newbie alfa owner and as it is my first car I haven´t done too much DIY work.

I´ve just bought a timing light ("classic" not with rpm or advabnce measurements), a synchrometer and a colortune.

First I did the ignition timing, and set the timing at idle using the light with the P mark of the crank pulley. Then I sprayed carb cleaner by the carb´s mounts to see if I had any leaks but din´t find any, the car idled smoothly. To be sure, I disconnected the carb support rod and moved the carbs up and down to see if there was a change in the idle, as nothing happened I proceeded.
Secondly, I was going to set up the carbs since I had a smog test and they were crap! I disconnected the linkage, unscrew the balancing screw and the idle screw completely. Then I ajusted the balancing screw until it made contact with the lever, and did the same with the idle screw.
Thirdly, I adjusted the idle mixture screws completly and give them 5 turns out, reconnnected the linkage and started the car and started balancing the carbs.

I´ve had trouble to get a smooth idle, or make the car hold the idle, so it has been very difficult to balance them. Although I adjusted the idle screw the idle remaind the same, if I accelerated the car, when the rpms went down the car remaind at 2000rpm (I think that was the real idle which was set) and then solwly went down to my erratic idle. As it was geting dark I stopped.

I don´t know what to do, how to fix it, or if I have done something wrong. Please help!!

The car has twin Dellorto DHLA 40 carbs with Ram flo filters, cams and headers (donpt know the specs as they came with the car), bosch electronic distributor and Mallory Hy-fire 6AL ignition.
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I re-checked the ignition timing. Then started using the colortune and the car`s idle went up, I re-adjusted it and continued using the colortune, re-checked carb balance and everything was ok.

Now I am confident with the carb`s set up, the car will mantain a very low idle speed, it is as smooth as a ported head!! never felt the car this way!!
Hi Ennio,

At how many turns in is your idle adjustement screw set? I've noticed that on my DHLA 40F, if the screw is in more than 1.5 turns, the RPM don't drop back down quickly enough after being revved. It sounds like you got to the right set up already though. Congrats.
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