I imagine the carburation is fine.
I would suspect a vacuum leak or iginition problems.
I would disconnect and plug all the vacuum accessories and recheck the
vacuum gauge. I would also spray some carb cleaner around the base
gaskets to make sure one of them aren't leaking. (It wouldn't hurt to
have a fire extinguisher nearby and to be wearing safety goggles.)
I'd go down to Sears and buy their timing light with adjustable advance.
Then I would rev the motor up to about 3,500 and measure the total
advance. It likely should be 30 to 35 degrees.
I would also determine exactly where TDC is on the first piston and make
sure the timing pointer agrees. Setting the valve timing wouldn't hurt
either.
If you are not aware that the car ever ran right, I would check the
valve timing to see if the intake valve is opening somewhere close to
the stock cam specs.
I would replace the plugs, if not new, and gap them to spec. I would
measure the resistance of the plug wires. I would also suspect the coil.
If it couldn't throw a 1/2 inch arc off the high tension wire I would
replace it.
I'm not too impressed with the vacuum numbers. Perhaps I would loosen
the distributor clamp and, at idle, rotate the distributor back and
forth and see what the vacuum readings do -- you should be able to
increase the vacuum quite a bit. When you adjust the timing for maximum
vacuum, I would then recheck the timing to see where it was at (it'll
likely now be a little too far advanced for high speed). I'd then use
the adjustable timing light to check timing at 3,500 rpm. Normal would
be around 35 although John Twist says up to 45 is normal
(http://www.universitymotorsltd.com/tech/tech031.htm).
With the engine hot I would do a compression test to make sure all the
readings are even. If I don't know much about the car, I'd also do a
leak-down test to see where leakage might be attributed if the
compression check numbers vary much.
Once all of that is done, and if everything checks out okay, I would
then suspect the carb. It's your car and your money and this advice is
free.
Do your driveablilty tests with the air cleaner installed.
--
Bob Allen, Kansas City
"When you suspect carburation problems, check the carbs last."
Rick Guynn wrote:
> Thanks to all for the suggestions I have received so far concerning my
> hesitation problem on the 'B ('79 engine, weber DGAV). Here's what it was
> (and still is) doing:
>
> This is all from running in the garage... I don;t know what it will do under
>actual
> load conditions....
>
> Idles well
> revs to high RPM's smoothly as long as you take it slowly
> bogs and backfires when you try to accelerate suddenly.
> revs properly during acceleration if the choke is kept mostly closed.
<snip>
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