TeeScott
Active Member
Gents, I have previously posted about "issues" with my 73 340 Rally challenger that I bought a little over 2 years ago in "fair" shape with orig. eng/trans and 92K miles. Car had been mostly sitting for the previous 12-13 years with semi-regular starting and drives around the block. As expected, I have had to do a lot of refurb/replacement work on items like tires, brakes, master cylinder, suspension/sway bar bushings, hoses, belts, radiator, steering pump and entire steering unit, carb, front end components, rear leaf springs, etc., etc....
Car is now driving/braking/shifting very nice (just swapped the orig. 3:91 diff gears for 3:23s and it makes a world of difference in its "cruise-ability."). Car uses practically zero oil, runs on the cool side and has no detectable blow-by or other signs of extensive wear. Current carb is a 600cfm Edelbrock that operated with no apparent problems when a friend of mine removed it from his car about a year before I installed it.
MY CURRENT PROBLEM: is to try and resolve a nagging engine "stumble/miss" that occurs whenever idling(fast or slow), or when driving down the road at a steady pace (from 10-~35 mph) or under a light throttle. RPMs fluctuate errratically 100-150 rpms when idling at ~2000 rpm. (see movie clip of tach movement if i can get it added to this note). Under hard-throttle, this stumble is not detectable/gone and the engine runs/pulls smoothly from idle until whenever I let off the gas.
My troubleshooting so far over the past 4-6 months:
-New drop-in replacement distributor, electronic ignition module, voltage regulator and ignition resistor from Mancini
-New plugs, distributor cap, and swap out of plug wires
-New fuel pump, filters and hoses under the hood
-New vacuum hoses to distributor, PCV and brake diaphragm.
-tightened intake bolts(a little) & sprayed WD-40 around the intake to see if there was a vacuum leak
-Just performed a full compression test (engine slightly warm) and checked the color of all plugs.(see pics)
THOUGHTS:
1) My carb has a minor vacuum leak or it is not operating correctly?
2) There is a minor vacuum leak somewhere around the intake mounting flange?
3) Some other electrical issue at low rpms/load?
4) some internal part(s) are worn/loose such as timing chain, etc..
5) My lowest compression cylinder (#2) is low enough to cause this erratic stumble? (I included a pic of the #2 spark plug along with a few others for comparison. #2 was one of the lightest brown in color but none were black or oily which I believe tells me that the bottom end/rings are in good shape.)
THX for any suggestions.
TeeScott
Car is now driving/braking/shifting very nice (just swapped the orig. 3:91 diff gears for 3:23s and it makes a world of difference in its "cruise-ability."). Car uses practically zero oil, runs on the cool side and has no detectable blow-by or other signs of extensive wear. Current carb is a 600cfm Edelbrock that operated with no apparent problems when a friend of mine removed it from his car about a year before I installed it.
MY CURRENT PROBLEM: is to try and resolve a nagging engine "stumble/miss" that occurs whenever idling(fast or slow), or when driving down the road at a steady pace (from 10-~35 mph) or under a light throttle. RPMs fluctuate errratically 100-150 rpms when idling at ~2000 rpm. (see movie clip of tach movement if i can get it added to this note). Under hard-throttle, this stumble is not detectable/gone and the engine runs/pulls smoothly from idle until whenever I let off the gas.
My troubleshooting so far over the past 4-6 months:
-New drop-in replacement distributor, electronic ignition module, voltage regulator and ignition resistor from Mancini
-New plugs, distributor cap, and swap out of plug wires
-New fuel pump, filters and hoses under the hood
-New vacuum hoses to distributor, PCV and brake diaphragm.
-tightened intake bolts(a little) & sprayed WD-40 around the intake to see if there was a vacuum leak
-Just performed a full compression test (engine slightly warm) and checked the color of all plugs.(see pics)
THOUGHTS:
1) My carb has a minor vacuum leak or it is not operating correctly?
2) There is a minor vacuum leak somewhere around the intake mounting flange?
3) Some other electrical issue at low rpms/load?
4) some internal part(s) are worn/loose such as timing chain, etc..
5) My lowest compression cylinder (#2) is low enough to cause this erratic stumble? (I included a pic of the #2 spark plug along with a few others for comparison. #2 was one of the lightest brown in color but none were black or oily which I believe tells me that the bottom end/rings are in good shape.)
THX for any suggestions.
TeeScott
