Carb question

So when the temps are hot 95 deg plus and the humidity is high( or just hot in general) we want to pull jet/fuel from the tune and maybe add some timing back in ( im just talking n/a ) ...correct ? So just like when im tuning my nitrous i can pull 1/2 lb of fuel out at a time w/ the regulator and ck plugs , so my question is can i do the same with the carb ? if i run a baseline of 7lbs on my q/f carb and i want to lean her out instead of changing the jets can i just remove 1/2lb of pressure to accomplish the same thing ?

Personally I wouldn't do it that way, Nick, but that's just me. I'd do it with jetting.

Carbs do not have actual "Fuel Pressure" in the Bowls, its atmospheric pressure. Fuel Pressure get the fuel to the bowls. Carbs rely on Vaccum to pull fuel into the engine and atmospheric pressure to push....

To answer your question, no changing fuel pressure willl not change the tune, except if you don't have enough fuel (can't keep up with fuel demand, Lean out) or add to much and know the needle of the seats and cause it to flood........

Just take the bowl off and jet for the weather, be sure to get it back on right and the accel pump arm is adjusted correctly...............I'm assuming thats what happened to your pump shot as you had the bowls off over the winter.


Hell get some alky injection and be a HeRo like a few us us are.......lots less to adjust with little room for error.................

Don't make this harder than it is........quit over thinking this. A guy may have to move the jets 1 or 2 once a damn year.

Lem Evans wrote:Don't make this harder than it is........quit over thinking this. A guy may have to move the jets 1 or 2 once a damn year.

....im not ...i promise ...... i just like to ask questions

bruno wrote:So when the temps are hot 95 deg plus and the humidity is high( or just hot in general) we want to pull jet/fuel from the tune and maybe add some timing back in ( im just talking n/a ) ...correct ? So just like when im tuning my nitrous i can pull 1/2 lb of fuel out at a time w/ the regulator and ck plugs , so my question is can i do the same with the carb ? if i run a baseline of 7lbs on my q/f carb and i want to lean her out instead of changing the jets can i just remove 1/2lb of pressure to accomplish the same thing ?

NO , take jet away, and maybe go up a deg or 2 in timing, nos you can take f presser away,but thats different


-rich

dfree383 wrote:Carbs do not have actual "Fuel Pressure" in the Bowls, its atmospheric pressure. Fuel Pressure get the fuel to the bowls. Carbs rely on Vaccum to pull fuel into the engine and atmospheric pressure to push....

To answer your question, no changing fuel pressure willl not change the tune, except if you don't have enough fuel (can't keep up with fuel demand, Lean out) or add to much and know the needle of the seats and cause it to flood........

lots of info ...thxs

Lowering the fuel pressure will lower the float level in the bowls slightly. This will tend to effect part throttle operation more than WOT, slowing down when the main starts a little bit. From best to worst conditions from what I've seen here is not more than 2 or 3 jet sizes. But with that said if the carburetor package is really crappy it might be more sensitive to these changes. I don't think that messing with the ignition timing will be of much of a benefit either.