New Carb Issues

[jefflock]

Just changed carbs from a Holley 700DP to a Quick Fuel 750. I'm having trouble with it wanting to try to backfire when you hammer it wide open. Any ideas?

 

[70aarcuda]

check the acelerator pump linkage ...that as soon as the throttle blade move the pump is squirting gas.....both front and rear pumps..

the rear secondaries usually do not start moving until you get the front throttle blades opened to 40 degrees..

also you might need to change squirter size....

 

[jefflock]

I found out today when I opened up the adjusting screws on the metering blocks it went away. Thar which has lead to another problem of being to rich at idle. I'm going to try changing the power valve to one with a lower rating.

 

[70aarcuda]

backfire are usually a lean condition

 

[jefflock]

Finally got it lined out. Went back to basics and started over. Hooked up a vacuum gauge and decided I needed to install a 2.5 power valve. Then I readjusted the initial timing and the 4 corner idle and have it running smoothly around 800 RPM. No more black smoke or back fire.

 

[jamesdart]

with no squirter change?