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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1966 Plymouth Valiant, 225, 3 on the tree, 8 1/4 3.21 sure grip, hyperpac, holley 650dp, holset h1c

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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1966 Plymouth Valiant, 225, 3 on the tree, 8 1/4 3.21 sure grip, hyperpac, holley 650dp, holset h1c

Maybe, a possible rich condition. Is this a vacuum secondary carb? What is the vacuum signal at this rpm?

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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Part of Tyrde-Browne Racing

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