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Problem:

My car hesitates almost exactly between 3000 and 3500 RPM in 2nd gear, and rarely in 3rd gear at about the same RPM.

Basic Details: I have a 3-speed automatic transmission, but the kickdown cable isn't attached and I drive it like a manual (w/o a clutch). Usually whenever I'm getting onto the interstate or highway, the whole system will stall out right between 3000 and 3500 RPM in 2nd, and stay there for a couple seconds. The harder I'm (attempting) accelerating, the worse the stall is and the longer it seems to take the drive system to "catch "again. If I let the car go to 3rd, and get past it, and back into 2nd, the car does fine from 3500 to 5000. It also seems to be fine if I get up to 3000, back off the gas for a second, and then floor it. It climbs right through the 3000-3500 range then. My suspicion is it's either fuel (pump) or transmission related.

It used to only happen once in a blue moon, but now I can almost count on it if I'm trying to accelerate quickly.

Extreme Details:

I got the car about 9 months ago after is sat in a guys yard for 3 years, and before that a good owner had it garage kept for about 20.

Engine: The engine isn't stock, a couple owners ago replaced it with a good 'ole Chevy 350, or so I was told. Not sure how to check displacement without pulling the engine and measuring the bore and stroke.

It's got a 4-barrel Edelbrock carb, pretty regular, and I've got it running a cold air intake that may be close to ram-air quality; it's getting plenty of air. (Maybe I'm running lean?)

The exhaust headers look like stock Chevy logs and I'll replace them eventually. The cat convert has been cut out and it's a pure straight back; sounds great.

Basically all emission control systems on the car were deleted before I got it actually, except for the PCV, and that valve is fine.

I'm running double-tipped platinum ACDelco spark plugs with a 0.40 gap. I picked platinum because I read they're the best option for this kind of engine, and mine have got the right heat rating. Not sure about the gap but it's the average of what I was reading I should do.

^

-Please tell me if there is a better gap I should do for this engine.-

Everything seems to work great and there's no obvious leaks from the engine; not since I replaced the valve cover gaskets.

No black smoke, so no ring leaks, yay.

I assume I've got the correct ignition timing. Something around 12 to 14 BTD at idle. I don't remember from when I got help tuning that.

Transmission:

The transmission is stock and appears to be a TH-350, based off of the pan.

I have yet to replace the filter and gasket.

There is a small leak and I've had to put more fluid in there every other month to keep it from running dry. I can't tell where the leak is coming from and I should have it checked out before something horrible happens, but I haven't gotten around to it; sue me.

If anybody's got ideas about what it could be, please say something! All and any help is greatly appreciated!

Thanks!
 

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Sure sounds like it is running out of fuel like you suspected. Especially when you say it just gets worse when you attemt to accelerate, all that does is open the carb more and lean out the mixture even more. When the transmission goes into third, the RPM drops and the demand for fuel goes down and what fuel is making it to the carb is suficient. When you back off the gas, then get back in it, you give the carb a chance to fill up. Could be the float is set too low or gets stuck in the up position, but I'd verify the fuel pump first. When you check your timing 10 to 14 initial seens fine, with no vacuum getting to the distributor. Make sure the mecanical advance is working by reving the engine with no vacuum to the distributor and verify the timing mark revs off the scale a good bit. The .040 gap seems ok, but maybe try .035 -.032 if nothing else seems to help.
 
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