1972 Float Adjustment ...

[jalexquijano]

2 hours ago, Mark Maras said:

 Yes. Then start it up, shut it down and check the fuel levels again in both carbs at 2 1/2 turns to be sure the fuel level isn't too high and pooling on top of the nozzles.

This means the gap between the float and lid  will be much less than .55 or 9/16 inches??????

[jalexquijano]

2 hours ago, Mark Maras said:

 Yes. Then start it up, shut it down and check the fuel levels again in both carbs at 2 1/2 turns to be sure the fuel level isn't too high and pooling on top of the nozzles.

This means the gap between the float and lid  will be much less than .55 or 9/16 inches??????

[Mark Maras]

20 minutes ago, jalexquijano said:

This means the gap between the float and lid  will be much less than .55 or 9/16 inches??????

 It would be better to see where the fuel level is before readjusting. Pull the domes and pistons (not the float covers). When you pull the choke on, the nozzles will lower and you'll be able to see the fuel level above the nozzles. Look and see if the rear carb fuel level is close to the front carb level.

[jalexquijano]

6 hours ago, Mark Maras said:

 It would be better to see where the fuel level is before readjusting. Pull the domes and pistons (not the float covers). When you pull the choke on, the nozzles will lower and you'll be able to see the fuel level above the nozzles. Look and see if the rear carb fuel level is close to the front carb level.

Just bent the tang a little bit more

[240260280]

J,

 

Can you mark a line on the outside of the fuel bowl where the top of the gas reaches? It is hard to tell from the angle of the photos?

[jalexquijano]

If i lift the piston up at 2000 rpm should the car stumble and shut down or should it keep running. Im afraid of bending the tang more and the fuel may overflow.

[Mark Maras]

@jalexquijano Prior to checking the mixture two things must be done first. The valve adjustment and ignition timing MUST BE CORRECT.

 Checking mixture. Use the piston lifting pin located under the side of the carbs. to check the fuel air mixture. With the engine running at working temperature, use the piston lifting pin to raise the piston about 1 mm (1/32"). If, while the piston is raised 1 mm, the engine speed increases briefly, then returns to normal, the mixture is correct. If the engine speed raises and stays high, the mixture is too rich. If, when the piston is lifted the engine speed drops or the engine dies, the mixture is too lean. Let us know what you discover.

[240260280]

12 minutes ago, Mark Maras said:

@jalexquijano Prior to checking the mixture two things must be done first. The valve adjustment and ignition timing MUST BE CORRECT.

 Checking mixture. Use the piston lifting pin located under the side of the carbs. to check the fuel air mixture. With the engine running at working temperature, use the piston lifting pin to raise the piston about 1 mm (1/32"). If, while the piston is raised 1 mm, the engine speed increases briefly, then returns to normal, the mixture is correct. If the engine speed raises and stays high, the mixture is too rich. If, when the piston is lifted the engine speed drops or the engine dies, the mixture is too lean. Let us know what you discover.

That is British hocus pocus.  Setting carbs with 1 /32" change in piston lift air flow at idle is optimistic.

[Mark Maras]

 @240260280 Glad you brought that up. I couldn't remember how far to lift the pistons. I looked for the proper distance but couldn't find it except a British SU site. What is the proper distance?

[240260280]

I read 1/64th of an inch (bad memory..I rechecked and 1/16th).  From my experience trying that technique, it is not accurate.

The only way to accurately  balance SU  carbs w/o air fuel meter is to run on one carb at a time and make sure each runs its 3 cylinders at the same rpm as the other carb AT THE SAME AIR FLOW.  This is achieved by measuring air flow and adjusting jet heights to match rpms. Then you read the plugs.

 

If you have an a/f meter, do the same and set the a/f for 28 to 29 when running on 3 cylinders at 2000 to 3000 rpm AT THE SAME AIR FLOW and re-check when driving under load.

 

If the needle does not meter the fuel from idle to acceleration under load correctly then there are only a few parameters to tune with (jet height, carb springs, carb piston weights, and damper oil) The only other way to tune is needle re-shape.

Edited March 21, 2018 by 240260280

[siteunseen]

13 hours ago, Mark Maras said:

 @240260280 Glad you brought that up. I couldn't remember how far to lift the pistons. I looked for the proper distance but couldn't find it except a British SU site. What is the proper distance?

My '72s have the little pin you push down to disable the carb.  Is that not a good disabler?  Should I call my therapist? 

[jalexquijano]

1 hour ago, siteunseen said:

My '72s have the little pin you push down to disable the carb.  Is that not a good disabler?  Should I call my therapist? 

You have not advised me on the level of the rear carb. Do i still need to bend the tang more?