I have had this top end miss for almost 2 years now, and I believe I have figured it out. If I floor the gas, the car will start to miss around 3k rpms, but if I back off slightly for a moment, and gradually increase the throttle, I can wind it up past 5k everytime. This would leave me to believe my fuel pump can't keep up. It's a holley red electric, and the carb is a 650DP holley. At idle, the pressure is normal, tried checking it while driving, but the needle bounced around the whole time. Should I try a bigger electric pump, or get a new eccentric, and go back to a manual pump? The holley pump sounds a little weaker after it's been in use for a while, and there aren't any heat sources close by, the exhaust goes out the side in front of rear wheels, and the pump is mounted under the car behind the axle. I have already had the timing checked and the ignition sytem. What would you guys do next? I was thinking a mechanical pump would be more reliable as rpm's increase.
Think I know what the problem is, but still unsure how to fix it.
sycostang67
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I have had this top end miss for almost 2 years now, and I believe I have figured it out. If I floor the gas, the car will start to miss around 3k rpms, but if I back off slightly for a moment, and gradually increase the throttle, I can wind it up past 5k everytime. This would leave me to believe my fuel pump can't keep up. It's a holley red electric, and the carb is a 650DP holley. At idle, the pressure is normal, tried checking it while driving, but the needle bounced around the whole time. Should I try a bigger electric pump, or get a new eccentric, and go back to a manual pump? The holley pump sounds a little weaker after it's been in use for a while, and there aren't any heat sources close by, the exhaust goes out the side in front of rear wheels, and the pump is mounted under the car behind the axle. I have already had the timing checked and the ignition sytem. What would you guys do next? I was thinking a mechanical pump would be more reliable as rpm's increase.
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1,898 Posts
My car would do the same thing but at around 2000-2500 RPM. It would go up steadily, then seem to hesitate and sort of "cough" at that point, then continue increasing steadily again.
It turned out to be my ignition system. My old mech had disconnected the vacumm line to the dizzy and had my timing all off! Took it to my old shop teacher and told me to change the timing and hook up that vac. line. Guess what? That problem ALMOST went away. My dizzy is all screwed up so that's why it still does it every ONCE in a while when I gun it too hard and too fast. I could almost bet you that when I change my dizzy problem will be fixed.
But, you said you already checked your ignition system...so I'm not sure. Maybe double check it? Good luck!
It turned out to be my ignition system. My old mech had disconnected the vacumm line to the dizzy and had my timing all off! Took it to my old shop teacher and told me to change the timing and hook up that vac. line. Guess what? That problem ALMOST went away. My dizzy is all screwed up so that's why it still does it every ONCE in a while when I gun it too hard and too fast. I could almost bet you that when I change my dizzy problem will be fixed.
But, you said you already checked your ignition system...so I'm not sure. Maybe double check it? Good luck!
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298 Posts
If I read your website correctly you have a Holley 650DP.
Check the floats, they might be sticking.
Check the floats, they might be sticking.
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