Everything You Always Wanted To Know...
Posted: Wed Aug 03, 2005 7:53 pm
about adjusting the SU carbs on, specifically, the R16, but I'm sure this technical jargon would apply to 2-liters as well. (This is presented in a light-hearted mood, so I don't want a bunch of shi...er...guff (yeah! that's it, "guff") coming my way.
(The following is word-for-word from
SERVICE MANUAL
DATSUN SPORTS
MODEL
SP311 SERIES
complete with grammatical errors):
INSTRUCTIONS FOR BALANCING TWIN HITACHI
HJB-38-W VARIABLE VENTURI SIDE DRAFT
CARBURETOR
Method A
( 1 ) Remove air cleaner.
( 2 ) Disconnect throttle connections of both carburetors.
( 3 ) On the front carburetor (nearest radiator) set idle screw so that tachometer reading is 500 RPM. If you do not have an instrument for balancing multiple carburetors, use a length of plastic hose, 1/2 inch diameter, and place at open horn of carburetor, and at your ear. Listen to sound of air entering carburetor.
( 4 ) Move to second carburetor and follow same procedure of listening to air entering this carburetor. If the sound is exactly the same as the front carburetor, then they are synchronized. If not, then adjust the idle screw until they have the same sound.
( 5 ) Now if reading of the tachometer has changed, you must move both idle screws until you have both carburetors hissing the same tone (bold type mine) and the RPM is not more than 650.
You have now synchronized the throttle opening of dual carburetors.
( 6 ) We will now proceed to adjust and synchronize the fuel flow of both carburetors. Start with the front carburetor adjustment.
With the engine running at 600 RPM, lift the piston of the back carburetor 1/2 inch. (This will make the carburetor inoperative.) If engine stalls, then you must richen the front carburetor until it will keep the engine running as if it were firing only two cylinders, rough but a steady beat.
Now repeat this same procedure or lifting the piston on the front carburetor, and adjust the mixture of the back carburetor.
( 7 ) You have now synchronized your air fuel ratio in both carburetors.
You may find when this step is completed that RPM has increased on your tachometer: if so, go back to step and correct your idle to 600 RPM.
( 8 ) Next, adjust your throttle linkage connecting the carburetors with the throttle shaft mounted on the intake manifold.
Adjust the length of throttle link so that it will snap in place without changing RPM on the front carburetor.
Do this same operation with the link to the back carburetor.
Your engine should now run smoothly, providing the rest of your engine is properly tuned, such as valves, points, plugs, condenser, and ignition timing properly set.
There you have it, clear as mud.
(The following is word-for-word from
SERVICE MANUAL
DATSUN SPORTS
MODEL
SP311 SERIES
complete with grammatical errors):
INSTRUCTIONS FOR BALANCING TWIN HITACHI
HJB-38-W VARIABLE VENTURI SIDE DRAFT
CARBURETOR
Method A
( 1 ) Remove air cleaner.
( 2 ) Disconnect throttle connections of both carburetors.
( 3 ) On the front carburetor (nearest radiator) set idle screw so that tachometer reading is 500 RPM. If you do not have an instrument for balancing multiple carburetors, use a length of plastic hose, 1/2 inch diameter, and place at open horn of carburetor, and at your ear. Listen to sound of air entering carburetor.
( 4 ) Move to second carburetor and follow same procedure of listening to air entering this carburetor. If the sound is exactly the same as the front carburetor, then they are synchronized. If not, then adjust the idle screw until they have the same sound.
( 5 ) Now if reading of the tachometer has changed, you must move both idle screws until you have both carburetors hissing the same tone (bold type mine) and the RPM is not more than 650.
You have now synchronized the throttle opening of dual carburetors.
( 6 ) We will now proceed to adjust and synchronize the fuel flow of both carburetors. Start with the front carburetor adjustment.
With the engine running at 600 RPM, lift the piston of the back carburetor 1/2 inch. (This will make the carburetor inoperative.) If engine stalls, then you must richen the front carburetor until it will keep the engine running as if it were firing only two cylinders, rough but a steady beat.
Now repeat this same procedure or lifting the piston on the front carburetor, and adjust the mixture of the back carburetor.
( 7 ) You have now synchronized your air fuel ratio in both carburetors.
You may find when this step is completed that RPM has increased on your tachometer: if so, go back to step and correct your idle to 600 RPM.
( 8 ) Next, adjust your throttle linkage connecting the carburetors with the throttle shaft mounted on the intake manifold.
Adjust the length of throttle link so that it will snap in place without changing RPM on the front carburetor.
Do this same operation with the link to the back carburetor.
Your engine should now run smoothly, providing the rest of your engine is properly tuned, such as valves, points, plugs, condenser, and ignition timing properly set.
There you have it, clear as mud.