<VV> Spyder Low RPM Stalling

[Jim]

The Engine

I have a '64 Spyder convertible with a completely rebuilt '65 180 that I
installed in May.  Everything in the engine from the carb to the pressure
plate was either replaced, rebuilt, upgraded, or confirmed to be good.  I
have put several hundred miles on it since then for break-in before using
the turbo.  [The Spyder glove box booklet says 500 miles.].  I did have to
replace the mechanical fuel pump last month.  It was part of the original
engine rebuild which was run for 2 hours by the engine builder before being
stored.

 

"The Incident"

On Saturday, I took it to a club breakfast meeting at a restaurant about 15
miles from my house.  It ran normally.  [A air-cooled 911 driver went by me,
gave me a thumbs up and tapped the horn as I was turning into the
restaurant, so it was a nice start to the day!]

 

After about an hour in the restaurant, we parted and left.  I started the
Spyder and found that it was running roughly, and it stalled as I stopped at
the parking lot exit.  It restarted quickly, and I was on my way home.
However, as I let off the gas when I came to the first stop light, the
engine started sputtering and popping through the exhaust and almost stalled
again.  I had to put my heel on the brake and use my toe on the accelerator
to keep the RPM up and avoid stalling.  I had to do this all the way home
for every stop sign and traffic signal.  

 

When I accelerated through the gears and cruised in 4th, the car ran fine;
it was smooth with no hesitation and easily went up hills.  The speed limits
on my route ranged from 35 to 45.

 

My Diagnosis Attempt

After I returned home and let the car cool, I decided to swap the new, Crane
XR-700 ignition system for a known good, base-level Pertronix system.  No
difference; the engine still wouldn't idle and would stall.  I reinstalled
the Crane system and have been scratching my head ever since.  My thinking
was that something in the ignition wasn't working well at low RPM.

 

The engine would pop through the exhaust and have what sounded like a small
back fire on occasion when I would blip the throttle to keep it running.

 

I'd appreciate any suggestions on things for me to check to solve this
problem.

 

Jim Bartasevich

 
The two most important days in your life are the day you were born and the
day you find out why. - Mark Twain