Top end woes

Discussion in 'Fox 5.0 Mustang Tech' started by David Schwarz, Jan 1, 2004.

  1. Still trying to get all of the bugs out of the new motor. I have a favorite uphill onramp near my house where I can really get on it. Discovered today that at 5500 rpm, the motor starts to backfire big time, but is fine when I shift to the next gear. I'm using a MSD 6AL with the YS trim blower (11# boost at 5700 rpm based on dyno pull). My mechanic said I didn't need the MSD 6BTM bacause I don't have a detonation problem (and this is definitely not detonation, I've had that with the old motor and know the sound well). I should point out that she seems to run fine on level ground, though I haven't had a chance to really test this carefully yet :rolleyes: .

    So what's causing the top end backfire/sputter. Could this be related to the absence of a boost timing master? I don't want to damage my new motor before it even sees its first trip to the track.
  2. might be just cause you have hit the limit of your engine could if be caused by floating lifters? i loose it around there too.
  3. Yes...floating valves or fuel pump maybe...mine used to back fire when it was lean...many things will cause BF