Wide band A/F gauge ideal ratio at WOT
April 2nd, 2013, 06:26 PM
#5
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Location: Rogues Island, USA
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Carbs run on atmospheric pressure. The fuel pump just keeps the bowl full. I would first find out what your fuel pressure is throughout an acceleration run. You'd want it to stay between 5-7 the whole time. Volume is also a function but stock pumps have supplied enough gpm for most high performance cars for decades.
Is the fuel filter clogged or the fuel line? I've had two cars benefit greatly from blowing out the fuel lines, both were clogged. One was the blocked fuel line and a collapsed sock in the tank. The other, who knows but it worked well afterward. The inside of the carb could be dirty also. Is it a stock Rochester Quadrajet?
Is the fuel filter clogged or the fuel line? I've had two cars benefit greatly from blowing out the fuel lines, both were clogged. One was the blocked fuel line and a collapsed sock in the tank. The other, who knows but it worked well afterward. The inside of the carb could be dirty also. Is it a stock Rochester Quadrajet?
April 2nd, 2013, 06:52 PM
#6
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holley 750 DP. New fuel filter. I have a fuel pressure gauge but it is on the fuel rail.
If I move to a high GPM fuel pump it will cost $40. Might be worth trouble shooting that before replacing all the fuel lines?
Engine is about 420HP at the crank. C heads ported and a mild cam. Holley Street dominator manifold. Nothing too radical.
Car noses over at around 95mph. A/F spikes at that point.
Before that it runs great.
If I move to a high GPM fuel pump it will cost $40. Might be worth trouble shooting that before replacing all the fuel lines?
Engine is about 420HP at the crank. C heads ported and a mild cam. Holley Street dominator manifold. Nothing too radical.
Car noses over at around 95mph. A/F spikes at that point.
Before that it runs great.
April 2nd, 2013, 06:57 PM
#8
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Location: Rogues Island, USA
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Things I'd check on a Holley:
Float levels, power valve (both of them since you have a double pumper), are you running an air cleaner?, make sure you check the pressure after the filter.
I'll probably think of more
Float levels, power valve (both of them since you have a double pumper), are you running an air cleaner?, make sure you check the pressure after the filter.
I'll probably think of more
April 3rd, 2013, 11:59 AM
#11
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Location: Rogues Island, USA
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I'm going to rule out power valves because you're lean the whole run. Even if they had ruptured it would run rich at other times and you'd notice it. I'm thinking main jets. Go up at least two sizes front and rear and see what that does.
It does sound like you are running out of fuel in the bowl with the way you describe it nosing over. The jets are probably being uncovered in the rear bowl for sure. Set the floats and maybe even go a bit higher in the rear and see what happens. You may need jet extensions also.
It does sound like you are running out of fuel in the bowl with the way you describe it nosing over. The jets are probably being uncovered in the rear bowl for sure. Set the floats and maybe even go a bit higher in the rear and see what happens. You may need jet extensions also.
April 16th, 2013, 07:05 PM
#20
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OK. Front jets are 71 rear are 80. Front power valve is 6 and rear power valve is a plug.
I did notice the front bowl did not move free like it should. It was like it was hanging up on something or the bowl return spring was bad. This could be my problem.
I did notice the front bowl did not move free like it should. It was like it was hanging up on something or the bowl return spring was bad. This could be my problem.
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