Help Need Tuning

[33racer]

Need help with tuning of twin weber alfa 33.

[colcol]

First of all you need a carby synchroniser, they are about $60 off ebay, mine was that about that 30 years ago, you put it in the top of the carby air intake, and it measures the amount of air flowing through the carby, first you do the idling, there is a screw on each side that the throttle sits on it when idling, you adjust these two to lower or raise the idling speed, now you have to average it out, say on one bank, the reading may be 8 for say number one cylinder and 10 for number three cylinder, you average it out and you say nine for that bank, then you do the same for the other bank and you may get ten for number two cylinder and say twelve for number four cylinder, the average for that bank will be eleven, so then you look at the idling speed, i think it is 850 RPM for non air conditioned cars, 1,000 RPM for air conditioned cars, so you increase or decrease the idle by turning the idle screws clockwise to speedup or counter clockwise to slow it down, but at the same time making sure the carbys are averaging the same amount of flow for each bank, you will always get variations from the cylinders next to each other, just make sure the right bank and left bank are passing the same amount of air, Colin.

[colcol]

Now you have done the idling carby balance, you have to do the midrange balance, there is a screw on each side on the cross throttle assembly, that has clearance onto a arm, this is to adjust the balance, once the carbys are off the idling screws, they should have an average of about 1 mm clearance between the screw and the bracket arm, run the car up to about mid revs, that is about 3,000 RPM, and stick the carby synchroniser in the air intake and like in the first post, check the flow for either cylinder and average it out for that bank, now to adjust the synchronisation of the left bank to the right bank, you adjust the screws on the previously mentioned cross throttle, now to get the carbys synchronised, you will have to adjust one screw in and the other screw out, just make sure if you adjust one screw in say 1/4 off a turn clockwise, you will have to adjust the other side bank's screw 1/4 turn anti clockwise, so that when the carbys are passing the same amount of air at 3,000RPM, the average clearance on the screws is 1mm, Colin.

[colcol]

To check the clearance on the screw, have the engine off and use a feeler gauge under the screws to check the clearance, you most likely won't get 1 mm clearance per side, so once again you average it out to say 1,1 mm clearance on one side and ,9 mm clearance on the other side, all this has to be done with the spark plugs clean and firing and timing all where it should be and no blocked air cleaner or intake leaks anywhere and the tappet clearances all set, a compression test would be a good idea, just to see what the condition of the engine is, as its hard to tune a worn out motor, Colin.

[33racer]

Thanks for the info will give it a try.

[colcol]

Having another look at mine, the idle speed screws are on the carby itself and the midrange balance  screws are on the linkage, get yourself that carby balancer, well worth it, as i was told how difficult it is to balance twin carbys, not with this device, Colin.