I noticed when accelerating hard in 2nd gear (TH400) that the car started to hesitate and loose power at about 4500 RPM...did it many times...upon experimenting a little, I found that if I accelerated a little slower (easier on the pedal) but still took the RPM's up, it would climb to 6000 with no problem...but under hard acceleration, the problem came back...I noticed that fuel pressure would start to drop down from 4 1/2 (runs here most of the time) to 4, then 3, then it starts to stumble...does this every time, so it must be pressure related...how much pressure should I normally be running? Its a Holley mech. pump, (hi volume) 454 w/ Holley 850 DP...Turbo400 tranny...I have to check the fuel filter yet (just thought of that!) but assuming that doesnt do it, should I just try bumping up the pressure on the regulator? I understand Holley carbs can accept 7 lbs. with no problems? What do you guys think? John

I would check the fuel filter, and I would check float level first.

Rocky Hill

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A Man And His Chevelle!
It's A Beautiful Thing.

My66SS (http://www.geocities.com/rocks66ss)

I would think that bumping up the fuel pressure would not help since the fuel pump can't deliver 4.5 psi very long anyway.I would check your filter like Rocky said.
Also if the ignition system is weak{bad plugs or whatever}it could missfire under hard acceleration and not miss under lighter acceleration up to the same speed.

I had a similar problem when my secondaries were out of adjustment and weren't opening at the right time.If I hit the gas, it would stumble and sputter, but if I gradually sped up it was fine.