HAHNAGON
Well-Known Member
- Local time
- 10:52 PM
- Joined
- Jun 26, 2023
- Messages
- 102
- Reaction score
- 31
- Location
- MOUNT VERNON, IN 47620
I am currently having an issue with a stumble or backfire only when in drive and when I try to accelerate quickly and stab the gas pedal. Engine stumbles, backfires and sometimes dies. My choke actually slammed shut once and I had to remove air cleaner pry it open on side of the road. Ok.....so it is a rebuilt 383 bb with very mild cam, aluminum edelbrock victor intake(because I already had this intake lying around), New Holley street demon 750cfm carb from Holley, new fuel pump, sending unit, tank, new oe style distributor and other distributors, etc. Restoration was finished this fall and everything is new. Current Distributor is a new factory style magnetic pickup with a Miller Ignition CD ignition box(like MSD 6al) and ronfrancis express wiring kit, super conductor wires, champion plugs gapped arouond .040, mopar performance coil(basically msd 2 with mopar sticker). At first I blamed timing because timing was advancing too much so I did disassemble distributor and weld some material in the advance slots to limit that a bit?? I also put 2 light springs in distributor, instead of one light and one heavy. Timing is currently set at 12 initial, 36-38 mechanical and I have plugged off the vacuum advance for now. I have tried adding timing and retarding timing. Engine runs very strong when in park. I can rev it to 6k all day and not have any issues but when I stab the gas under a load in drive it backfires or stumbles. I have also tuned with a vacuum gauge for max vacuum. Adjusted idle mixture with vacuum gauge more than once and reset to TDC on #1 and set timing again and again multiple times in hopes I missed something. I have also tried adjusting the accelerator pump linkage to notches 1, 2 and 3. Plugs look good and maybe a little on the rich side but my first guess is its not getting enough fuel but i find it hard to believe that a very mild 383 isn't getting enough fuel from a new 750 holley carb. Any recomendations? Discharge nozzle? Jet change? Or something else? Thank you.