DJ'S MJ Posted February 15, 2020 Share Posted February 15, 2020 I have a 1989 MJ. Rebuilt the engine. Now 9.4 to 1, Stage 2 cam, 58 mm TB, Pacesetter Header, 19 lb 4-hole injectors, and ported & polished head. At Idle, runs great and sounds even better through Thrush muffler. Accelerate and it backfires through TB?? Any one out there has a clue what to do? Link to comment Share on other sites More sharing options...
1989commanche Posted February 15, 2020 Share Posted February 15, 2020 Sounds like timing Link to comment Share on other sites More sharing options...
Warren Mohler Posted February 15, 2020 Share Posted February 15, 2020 are all intake valves seating proper? push rods too long, valve springs weak, was cam "broken in". How does it start. timing, how long since rebuild, any miles, has it done this from initial start up? Link to comment Share on other sites More sharing options...
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