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| rpm flutter https://www.slantsix.org/forum/viewtopic.php?t=49037 |
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| Author: | Junior [ Mon Jun 11, 2012 3:51 pm ] |
| Post subject: | rpm flutter |
while racing after i do my burnout and pull up to the line when i bring the rpm up to 2700 with the clutch in to get ready to launch it fluctuates 500 rpm.it revs up fine up to 2300 and will hold a steady rpm but once i go over that it starts. its almost like its bouncing off of a limiter. its not really a problem but im curious as to why it does it. |
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| Author: | Junior [ Mon Jun 11, 2012 3:53 pm ] |
| Post subject: | |
225 slant stock internals and head with a 4bbl 390 holley and shorty headers running open. car runs beautifully under normal driving conditions it only happens when im getting ready to launch |
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| Author: | kesteb [ Mon Jun 11, 2012 7:30 pm ] |
| Post subject: | |
Maybe, a possible rich condition. Is this a vacuum secondary carb? What is the vacuum signal at this rpm? |
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| Author: | ceej [ Mon Jun 11, 2012 7:35 pm ] |
| Post subject: | |
The pump will "wiggle" causing the accelerator pump to dribble fuel from the shooter. Try moving to screw hole number 2 on the pump cam. Make sure to recheck the pump adjustment after changing the pump cam position. A small amount of movement on the leading edge of the pump cam can cause this. Just a possibility... 2¢ CJ |
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| Author: | DusterIdiot [ Mon Jun 11, 2012 8:35 pm ] |
| Post subject: | x2 |
What is your vacc. reading at this level? Pump dribbling can be a cause (check your pump cam clearance), if the vacc reading is still high you might be pulling fuel out of the shooters as well (which may require the addition of a needle weight in the pump bore- something standard on the 600 dfm Holleys, but I've never seen them stock in the 8007's). I would also take a serious look at your timing as well, if you are running a stock points distributor that has not been degunked or a spring is broke your timing could bounce varying rpm. -D.Idiot |
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