Re: IML: Carb problems or what

[David Whitney <david.whitney@xxxxxxxxxxxx>]

The rough idle may not be directly related to the carb.  If it's missing
after changing all the things you mentioned and they were all done
correctly, I would start looking at the timing chain.  When you set the
timing, does the mark jump around or is it steady in one place?  Did you
have the vacuum advance disconnected and capped when you set the initial
advance?  P.S., it's easy to forget to reattach the hose once the initial
advance is set.

If you're satisfied that the initial advance is correct and the timing is
steady, then it's time to examine those "many adjustments".  Per the
Edelbrock folks, air/fuel mixture should be done with a vacuum gauge, then
low idle with a tachometer.  Those are the last two adjustments.  Anything
that's not done correctly before that could prevent you from being able to
make those adjustments properly.

Try running the engine without the air cleaner.  At low idle and at
operating temperature, the choke flap on the primary bores should be fully
open and the flap on the secondary bores should be fully closed (assuming
your aftermarket carb has vacuum operated secondaries vs. mechanical -- if
mechanical, the secondary throttle plate should be fully closed and no gas
should be visibly squirting from the secondary circuit).  Put your hand
over the primary bores, restricting the air flow.  If idle quality
improves, you are running lean (not enough fuel).  Assuming there is no
blockage in the carburetor's teeny tiny passages, that is generally an
indication of a vacuum leak -- there's not enough suction to draw fuel
through the carb's idle circuit.

The Edelbrock carb is largely a clone of the stock Carter.  The first
squish of the accelerator pump is a mechanical operation that forces fuel
into the primary bores (that's what happens when you pump the pedal -- it's
like priming the carb).  After that, manifold vacuum draws fuel through the
primary circuit -- not the idle circuit, because the choke is holding the
throttle plate open a bit.  The idle circuit only operates when the
throttle plate is closed.  The choke flap enhances vacuum by restricting
air flow through the top of the carb.

The other possibility is that  fuel is evaporating from the bowls
overnight, then the engine is starved for fuel until the fuel pump can get
more gas into the bowls.  It's a loooooong way from the tank to the carb.
You'd actually have to take the carb apart to check this -- the
Edelbrock/Carter does not have sight glasses.

Since both the problems you described could be due to insufficient manifold
vacuum, I lean toward a vacuum leak.  If it's not a vacuum leak, check the
primary throttle plate for full closure with no pressure on the gas pedal.
If I'm right, I recommend you get somebody else to do your carb work
because the shop should have caught this.

Sorry about the long-winded answer, but long distance troubleshooting
requires making some assumptions.

Happy motoring,

David




                                                                                                                                              
                      <casemark1@xxxxxxx>                                                                                                     
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                      02/22/2005 05:50 PM                                                                                                     
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Hi all, my newly restored 65 is having a rough time with the carb and idle
and I hope some of you experts can help.  The shop put on an Edelbrock 600
something series carb and did many adjustment per the Edelbrock folks but
I'm having a hard time with it after the car has sat overnight.  I pump it
a couple of times and then it starts right up but then dies very quickly
and then takes a long series of cranking before it will go.

Also, once warm, the car idles roughly.  The plugs, plug wires, points and
distributor cap are all new.  The rough idle feels like it's missing.  I
don't know if these things are related  but I sure would appreciate some
tips.

She sure is great to drive.  After almost 3 years I'm having a ball with
the car.  I get lots of thumbs up and smiles.

Casey
65 Crown 4 dr   "Clairee"



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