Interesting find this PM
Discussion
Took the air cleaner off so I could measure the throttle cable travel. I need the figure in order to design the crank on the efi throttle body.
Measured at closed then jammed the pedal down with a piece of wood.
Went to take the second measurement and things did not look right. I could not move the throttle any wider open but the butterfly was less than half open.
An hour later with the whole carb in bits on the bench I finally found a little plunger in the passageway from the secondary accelerator pump was jammed in its housing. This in turn was not allowing the pump to depress and its lever was stopping full opening of the butterfly.
Perhaps this is why my AFR reading goes to 20 when accelerating.
Steve
Measured at closed then jammed the pedal down with a piece of wood.
Went to take the second measurement and things did not look right. I could not move the throttle any wider open but the butterfly was less than half open.
An hour later with the whole carb in bits on the bench I finally found a little plunger in the passageway from the secondary accelerator pump was jammed in its housing. This in turn was not allowing the pump to depress and its lever was stopping full opening of the butterfly.
Perhaps this is why my AFR reading goes to 20 when accelerating.
Steve
Which model of carb is it Steve?
If when corrected, it resolves any previous running issues, will you still continue with EFI?
For several months Ive been in discussion with some very respected US SBC builder/racers. All of them disagree that a 500-600 HP small block 'needs' EFI in a road/race installation, to give consistent results.
Having committed to EFI I was surprised initially but after speaking further with some US carb Gurus it seems all new production/aftermarket carbs need fettling/blueprinting to release their full, intended potential.
Maybe there is merit in what the carb guys are claiming?
If when corrected, it resolves any previous running issues, will you still continue with EFI?
For several months Ive been in discussion with some very respected US SBC builder/racers. All of them disagree that a 500-600 HP small block 'needs' EFI in a road/race installation, to give consistent results.
Having committed to EFI I was surprised initially but after speaking further with some US carb Gurus it seems all new production/aftermarket carbs need fettling/blueprinting to release their full, intended potential.
Maybe there is merit in what the carb guys are claiming?
738 driver said:
Which model of carb is it Steve?
If when corrected, it resolves any previous running issues, will you still continue with EFI?
For several months Ive been in discussion with some very respected US SBC builder/racers. All of them disagree that a 500-600 HP small block 'needs' EFI in a road/race installation, to give consistent results.
Having committed to EFI I was surprised initially but after speaking further with some US carb Gurus it seems all new production/aftermarket carbs need fettling/blueprinting to release their full, intended potential.
Maybe there is merit in what the carb guys are claiming?
The carb is a Holley Model 4150 mechanical secondary double pumper 0-4780C.If when corrected, it resolves any previous running issues, will you still continue with EFI?
For several months Ive been in discussion with some very respected US SBC builder/racers. All of them disagree that a 500-600 HP small block 'needs' EFI in a road/race installation, to give consistent results.
Having committed to EFI I was surprised initially but after speaking further with some US carb Gurus it seems all new production/aftermarket carbs need fettling/blueprinting to release their full, intended potential.
Maybe there is merit in what the carb guys are claiming?
They may well be right that a carb can be fettled and correctly tuned to work well.
But....that assumes that you have a huge amount of experience plus a box full of main jets, secondary jets, power valves, accelerator jets, accelerator pumps, accelerator cams and a rolling road or dyno to do it on.
Once I have all the bits in place I will be able to do all I need with a laptop. Then, if I choose, I can have a session on a rolling road but doubt I will need it unless I want to nail the 'How many horses' question.
Steve
Steve: Just a point for you to consider. My original LS style throtle body worked with the ratios of the stock Ultima gas pedal throw. The Kinsler set up I now use did not. The Ultima pedal set up didn't have enough throw. Not the end of the earth, but something you migh face if you move to EFI. Lee
ROWDYRENAULT said:
Steve: Just a point for you to consider. My original LS style throtle body worked with the ratios of the stock Ultima gas pedal throw. The Kinsler set up I now use did not. The Ultima pedal set up didn't have enough throw. Not the end of the earth, but something you migh face if you move to EFI. Lee
That was the reason for taking the measurements.As it happens it appears to be spot on to the half mm.
Steve
Steve
I have 4150 double pumper 750 cfm 6.3L 500hp AM.SP . How far out are your idle screws ? I found mine ever so sensitive but now have relatively seamless progression from idle,1000rpm to rest of range . Away to check my butterflies now if I can afford one full deflection of the throttle pedal .
Frank
I have 4150 double pumper 750 cfm 6.3L 500hp AM.SP . How far out are your idle screws ? I found mine ever so sensitive but now have relatively seamless progression from idle,1000rpm to rest of range . Away to check my butterflies now if I can afford one full deflection of the throttle pedal .
Frank
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