440-6pack
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- Joined
- Oct 9, 2017
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Hi everyone,
I need your help!
I have a 1971 Challenger 440 6-pack, 4 speed. It was running great last fall. This spring when I took it out, it ran great the first week then slowly started hesitating on hard acceleration. Now when I stomp the gas from a rolling stop or downshift it sputters, pops and cuts in and out something fierce. However, it idle great when warm, revs up all day long in neutral and has lots of power if I accelerate slowly under load.
What I have done to date:
FUEL
1. Manifold reading at idle 24 inHg
2. Ported reading at idle 3 inHg
3. Ported reading 22-24 inHg but fluctuates +/- 2 inHg when I hold at 2500rpm
4. I tried a smoke test via the brake booster hose. Smoke just came out the top of the carbs...
TIMING
1. Base timing 15*@900 rpm, total mechanical advance at 3000rpm 38*, total with vacuum advance 55*
IGNITION
1. Mopar electronic ignition
2. New flame thrower coil. Tried my spare flame thrower and stock coil.
3. New Mopar spark plug wires
4. New champion cap, rotor and spark plugs gapped at .035
5. New distributor with reluctor set at .008 and .020 with full vacuum advance. I tried my spare (new) distributor. Neither had any play in the shaft.
6. New Mopar ignition box and voltage regulator. Also tried my new spare of both.
7. New NOS ignition switch and full reproduction wiring harness. I double checked all bulkhead connectors.
8. Tried 2 rebuilt alternators, both producing 13.5-14 volts
9. I’m not sure if related but the reproduction tachometer smoked and let go a couple weeks back. I installed a new aftermarket with factory wiring and no issues for 1 month.
ENGINE
1. C440 HP block, compression even at 155-160 psi in all cylinders. It appears there are “motor home” heads that only accept RV12YC plugs. Don’t think this is an issue as it ran fine last year...
2. No signs of burning oil but lots of dry carbon deposits in tail pipes and 4 of the eight spark plugs. cylinders 5,6,7,8 were fouled, 1,2,3,4 were lean.
If anyone has any insight on what the problem could be I would be forever grateful. The next things I will try are replacing the intake gaskets to eliminate any potential vacuum leak as-we’ll as disconnecting the secondary carbs in case they are malfunctioning.
Thanking you in advance!
I need your help!
I have a 1971 Challenger 440 6-pack, 4 speed. It was running great last fall. This spring when I took it out, it ran great the first week then slowly started hesitating on hard acceleration. Now when I stomp the gas from a rolling stop or downshift it sputters, pops and cuts in and out something fierce. However, it idle great when warm, revs up all day long in neutral and has lots of power if I accelerate slowly under load.
What I have done to date:
FUEL
- Changed fuel filter. I have an electric pump rated 5.5-9psi. I’m getting 5psi at the carbs. No return line.
- I’ve adjusted the floats to get a dribble from the port.
- I replaced the gas tank last year and have only run high octane (91-94)
- I installed a Holley refresh kit and 6.5 power valve, #31 squirter on main carb
- Installed the orange accelerator pump cam
- A/F adjustment screws at 2 turns for max vacuum 22inHg
1. Manifold reading at idle 24 inHg
2. Ported reading at idle 3 inHg
3. Ported reading 22-24 inHg but fluctuates +/- 2 inHg when I hold at 2500rpm
4. I tried a smoke test via the brake booster hose. Smoke just came out the top of the carbs...
TIMING
1. Base timing 15*@900 rpm, total mechanical advance at 3000rpm 38*, total with vacuum advance 55*
IGNITION
1. Mopar electronic ignition
2. New flame thrower coil. Tried my spare flame thrower and stock coil.
3. New Mopar spark plug wires
4. New champion cap, rotor and spark plugs gapped at .035
5. New distributor with reluctor set at .008 and .020 with full vacuum advance. I tried my spare (new) distributor. Neither had any play in the shaft.
6. New Mopar ignition box and voltage regulator. Also tried my new spare of both.
7. New NOS ignition switch and full reproduction wiring harness. I double checked all bulkhead connectors.
8. Tried 2 rebuilt alternators, both producing 13.5-14 volts
9. I’m not sure if related but the reproduction tachometer smoked and let go a couple weeks back. I installed a new aftermarket with factory wiring and no issues for 1 month.
ENGINE
1. C440 HP block, compression even at 155-160 psi in all cylinders. It appears there are “motor home” heads that only accept RV12YC plugs. Don’t think this is an issue as it ran fine last year...
2. No signs of burning oil but lots of dry carbon deposits in tail pipes and 4 of the eight spark plugs. cylinders 5,6,7,8 were fouled, 1,2,3,4 were lean.
If anyone has any insight on what the problem could be I would be forever grateful. The next things I will try are replacing the intake gaskets to eliminate any potential vacuum leak as-we’ll as disconnecting the secondary carbs in case they are malfunctioning.
Thanking you in advance!