16v alfa sprint runing 40mm 8v idf carbs

[baldy]

Hello, ive just joined this forum and it looks like this is the place to be for good information from people who really know what there talking about.
As you you can see from the title i have a little project on the go and my aim is to get the car to run as sweet as possible.
I have 40 idf carbs from a 8v 1.7 engine, same capacity as my own, i set the timing to 8 degrees between 500-1000 rpm as per book guide and ballanced both carbs with a syncronizer both on tickover stops and mid throttle no problems there, the air bleed screws are all out 1 3/4 turn this is what ive found to be the best place for a reasonable tickover any further out and black smoke from the exhaust and rough runing at idle.
When the engine is worm its quite good to drive below 3000 and no probs above that, however once up to full temp i get a small anoying stumble just on light gas between 1000 and 1500,i thought it may have been the pump jets , any help would be welcome thanks Lee

[77SudTi]

I get the same stumble on ,y 8V running the 40mm webers. It is most likely solved by using a larger idle jet as the 8V's lean out at around 1000 to 1500 rpm and ence suffer from the same flat spot. Enlargening the idle jets would more than likely correct this problem. Although probably best sorted out with the aid of a dyno.
Although the webers came from a 1.7L engine, the 16V has greater flow; more gas in and more gas out compared to the 8V motor. I would suggest the main jets should also be enlarged and new emulsion tubes also fitted to suit the 16V. I think its time you put your car on the dyno and played with jet sizes...

best of luck!

[77SudTi]

I get the same stumble on my 8V 1.7 running the 40mm webers. It is most likely solved by using a larger idle jet as the 8V's lean out at around 1000 to 1500 rpm and hence suffer from the same flat spot. Enlargening the idle jets would more than likely correct this problem. Although probably best sorted out with the aid of a dyno.
Although the webers came from a 1.7L engine, the 16V has greater flow; more gas in and more gas out compared to the 8V motor. I would suggest the main jets should also be enlarged and new emulsion tubes also fitted to suit the 16V. I think its time you put your car on the dyno and played with jet sizes...

best of luck!

(double post, no idea why!!)

[baldy]

Hi more info on ignition mod on page twelve of the sprint pictures thread.i just dropped the ignition timing down from 8 to 6 deg at 15 percent throttle opening at 1000 rpm on the map.and the car drives a lot better now on light throttle .

[Greek]

Thanks Baldy for the pics , we have them and we are discussing how we can make the same here....