Hey guys, i have a customers car thats driving me crazy. Im no stranger to small block chevys and g bodies but i have this customers el camino thats got me stumped. The car has an off idle stumble/ sometimes pops out the carb when you hit the throttle at lower speeds. Once the car is moving its fine and once it gets over 2000 rpm it moves just fine. It does this somewhat interminently. Customer stated its done this since he got the car a year ago.
Car has following mods:
stock 305 (unopened from what i see)
Edelbrock 600 electric choke
performer intake
HEI distributor with the msd cap conversion to use an external blaster coil (vacuum advance, not the computer distributor)
MSD 6a box
Air pump delete
True dual exhaust
3.23 gears
Heres what ive fixed and done:
Retimed distributor from ported to advance back and forth, varying base timing between 4-8, no change
Adjusted carb better (carb is fairly new and looks like no one has played with it), no change
Pulled distributor apart to find broken spring and sticky weights, replaced distributor with reman unit, no change
Pulled valve covers, checked all springs and valve adjustment (thought it could have been a tight valve or broken spring) all is well
Fixed 2 vacuum leaks, no change.
Checked fuel psi, has 6 psi, even changed fuel pump with known good mechanical pump to see if it was leaning out, no change
Car idles great, revs great with no load, idles and revs smoother with all the repairs i made, still has the stumble/pop
Hooked vacuum gauge up, sits at 18 in/hg, with minor rapid flux between 18 and 17 1/2 (seems normal to me), responds fine when reved up.
Heres my last ideas:
Bypass the external coil and msd box by putting a normal coil on it and putting the ignition module assembly back in the dist. Maybe msd box is faulty or this external setup is arcing somewhere.
Pull the timing cover (dont wanna do this) and see if the chain is way stretched
Any other ideas? Ive been so lost in FI and locked out billet distributors/holleys that maybe im missing something basic with the old HEI set up and carter/edelbrock carbs. Its more stressful because its a customers car and not mine. Hes used to the car doing this but i wont let it leave until its right
Any help would be awesome! Thanks
Car has following mods:
stock 305 (unopened from what i see)
Edelbrock 600 electric choke
performer intake
HEI distributor with the msd cap conversion to use an external blaster coil (vacuum advance, not the computer distributor)
MSD 6a box
Air pump delete
True dual exhaust
3.23 gears
Heres what ive fixed and done:
Retimed distributor from ported to advance back and forth, varying base timing between 4-8, no change
Adjusted carb better (carb is fairly new and looks like no one has played with it), no change
Pulled distributor apart to find broken spring and sticky weights, replaced distributor with reman unit, no change
Pulled valve covers, checked all springs and valve adjustment (thought it could have been a tight valve or broken spring) all is well
Fixed 2 vacuum leaks, no change.
Checked fuel psi, has 6 psi, even changed fuel pump with known good mechanical pump to see if it was leaning out, no change
Car idles great, revs great with no load, idles and revs smoother with all the repairs i made, still has the stumble/pop
Hooked vacuum gauge up, sits at 18 in/hg, with minor rapid flux between 18 and 17 1/2 (seems normal to me), responds fine when reved up.
Heres my last ideas:
Bypass the external coil and msd box by putting a normal coil on it and putting the ignition module assembly back in the dist. Maybe msd box is faulty or this external setup is arcing somewhere.
Pull the timing cover (dont wanna do this) and see if the chain is way stretched
Any other ideas? Ive been so lost in FI and locked out billet distributors/holleys that maybe im missing something basic with the old HEI set up and carter/edelbrock carbs. Its more stressful because its a customers car and not mine. Hes used to the car doing this but i wont let it leave until its right
Any help would be awesome! Thanks
