Engine hesitation - Impala Tech
Engine General Engine Discussion.

LinkBack Thread Tools
post #1 of 8 (permalink) Old 06-09-2010, 11:42 PM Thread Starter
Join Date: May 2010
Location: California
Posts: 89
Blog Entries: 1
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,
sandiegohat is offline  
Sponsored Links
post #2 of 8 (permalink) Old 06-10-2010, 12:59 PM
Join Date: Oct 2009
Location: Ohio
Posts: 61
Blog Entries: 8
see this thread...
Throttle hesitation

Check out my blog..1964 restore...

1953 Chevrolet 3100 Pickup
261ci Stovebolt.

1966 Chevrolet El Camino
327ci Mouse.

1964 Chevrolet Impala
283ci little Mouse.

Next on the list....1962 Impala convertible..
Beetle is offline  
post #3 of 8 (permalink) Old 06-10-2010, 05:34 PM
Join Date: Jan 2006
Posts: 11,059
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
Big Dave is online now  
post #4 of 8 (permalink) Old 06-10-2010, 07:11 PM Thread Starter
Join Date: May 2010
Location: California
Posts: 89
Blog Entries: 1
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,


Last edited by sandiegohat; 06-10-2010 at 07:13 PM. Reason: Grammer
sandiegohat is offline  
post #5 of 8 (permalink) Old 06-14-2010, 01:02 PM
Senior Member
Join Date: Jun 2008
Location: Near Chicago
Posts: 703
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.
1968 Caprice 396 is offline  
post #6 of 8 (permalink) Old 06-14-2010, 03:38 PM
Join Date: Apr 2010
Location: Pell City, AL
Posts: 20
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.
Wicked is offline  
post #7 of 8 (permalink) Old 07-06-2010, 03:31 PM
Senior Member
Join Date: Jul 2010
Location: Suffolk, VA
Posts: 143
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!
bowtyebob is offline  
post #8 of 8 (permalink) Old 07-06-2010, 06:09 PM Thread Starter
Join Date: May 2010
Location: California
Posts: 89
Blog Entries: 1
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,


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)
sandiegohat is offline  
Sponsored Links

Quick Reply

Register Now

In order to be able to post messages on the Impala Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome