Engine hesitation - Impala Tech
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post #1 of 8 (permalink) Old 06-09-2010, 11:42 PM Thread Starter
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Engine hesitation

Help please!
I own a 64 impala SS with a 327/2 speed pg, and what looks like a stock carb.i recently purchased the car and noticed that it has a major hesitation issue when I accelerate. When I got it home I changed the plugs, fuel filters, and inspected the distributor and the points. Everything check out except for the fuel filters. They had rusty and large sized rust flakes. I replace the carb fuel filter and also the inline. It still hesitates as soon as I hit the gas. Once it gets past that point it is smooth sailing. I then checked the timing and noticed that it was advanced a little. I adjusted the timing and as soon as I tried to to drive it the engine kept choking off and would not even move. It got to the poimt where I had to set the timing to where it was to keep it from cutting off. Here are some more symptoms:

black watery stuff out of the tail pipe at start up.
Idles kind of low.
The carb has what looks like varnish, waxy stuff all over it.
When I stomp on the gas it will choke itself off.
Only lets me slowly accelerate all the way.

If anyone is having or had issues like these please help. I'm thinking of buyinf a new carb and new fuel tank. I think tue fuel tank is corrupting the fuel. My question a out the tank is. Shouldn't the fuel filters be stopping all that trash from getting through?

Semper Fi,
Hector
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post #2 of 8 (permalink) Old 06-10-2010, 12:59 PM
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see this thread...
Throttle hesitation

Check out my blog..1964 restore...
http://www.impalas.net/forums/blogs/beetle/

1953 Chevrolet 3100 Pickup
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1964 Chevrolet Impala
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post #3 of 8 (permalink) Old 06-10-2010, 05:34 PM
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Sounds like you are running pig rich.

What kind of carb are you running?

Is it hard starting? Or a better question is if it sits over night; before you crank it will the gas accelerator pump spray more than a shot or two before it runs dry? If so you probably have a Welch plug out on the bottom of your carb's fuel bowl that is allowing raw gas to flood the motor (they fall out over time from heat cycling, and dissimilar metals expanding at a different rate of speed allowing it to work it's way out).

Retarding timing always makes a motor act more sluggish to not wanting to run at all. Motor's like a lot of initial timing but we have to use restraint to keep the motor from getting into detonation with changing atmospheric conditions and fuel quality.

Big Dave
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post #4 of 8 (permalink) Old 06-10-2010, 07:11 PM Thread Starter
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Big Dave,
The car starts right up with no problem, sometimes it will make me pump it a few times but for the most part it's easy starting. It's a two barrell rochester. As far as the how many 'shots the carb is putting out before it goes out", how would I find out? In addition, what is the possibility of the gas tank being a source of the problem?

I was thinking of getting either a holley or edelbrock 650 however, if rebuilding the carb can be just as good I would go that route first. I'm trying to keep the cost down ias much as possible.


Semper Fi,

Hector

Last edited by sandiegohat; 06-10-2010 at 07:13 PM. Reason: Grammer
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post #5 of 8 (permalink) Old 06-14-2010, 01:02 PM
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Accelerator pump diaphram is shot. For a carb to control air/fuel from idle to to acceleration the carb has to overcome the sudden input of air when the butterflies open. That's where you need a squirt of fuel from the accel pump, otherwise it will bog until the main circuit kicks in.
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post #6 of 8 (permalink) Old 06-14-2010, 03:38 PM
 
 
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Mine does the same thing(on my '68 Bel Air Wagon)....I think my QJ carb is stock too.

If I am cruising and punch it, it downshifts and revs up and pulls decent without hesitation. If I'm just barely rolling and punch it, it will sound like half of the cylinders are dead...My guess is also its dumping fuel and poutting the fire out.
I plan to go to an LS1 soon but may invest the few bucks in a carb until then.
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post #7 of 8 (permalink) Old 07-06-2010, 03:31 PM
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Hector,
Verify that you have the correct carb. It should be a Carter AFB. If it is the orininal it will be a modle 3721S. I had the same problem and found a GM service bulletin daye 5/28/64 addressing this issue. The problem was resolved with an upgrade to the carb making it a 3821SA. The upgrade was for different primary and secondary vunturi clusters, metering rods and primary and secondary jets. I fould a 3721SA on ebay, took it apart and cleaned and then installed the SA parts inti my November '63 built 3721S making it an SA. Problem solved!
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post #8 of 8 (permalink) Old 07-06-2010, 06:09 PM Thread Starter
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BowtieBob,
i'm definetly going to look into it when I return from my short deployment later this week. I will post my findings at a later date. Thankyou all for the support

Semper Fi,

Hector

1964 Impala SS HT
2007 Tahoe LTZ
2006 Kawasaki ZX10
2003 Yamaha R1 (sold)
1995 Impala SS
1993 Tahoe GT (sold)
1978 Buick Regal (sold)
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