LEB Ben
Arrogant A-hole At-Large
...and my girl ain't one of 'em. Seriously though, trying to do a little trouble shooting and have a few questions, mainly fuel delivery/carb related I believe.
1) The biggest problem of all is, there seems to be a backfiring issue. It's not a consistent problem, but it seems to happen most often when I let off the gas to coast or slow down, then when I go to get back on the throttle I get pop/backfire and then it'll accelerate. It also seems to happen at shift changes as well. It's worse when the vehicle is cold, but as I said...the problem is not consistent at all.
2) When traveling at sub 35mph speeds, and I go to give it a little bit of gas, it will sputter/stutter a little bit and then resume properly...not that big of a deal...just more of an annoyance.
3) There have been 5 times now in about 500 miles of driving where I will start the vehicle and start driving and after a few hundred feet the vehicle will die. It's almost like it's using whatever fuel is in the bowl, and then like there was no fuel in the outlet line from the fuel pump.
4) I've noticed a new vibration...or wobble rather...that wasn't there with the old engine between 60-70mph. Not sure if this is engine related, but it wasn't there until the swap.
5) Now I know these things aren't gas sippers, and I'm not complaining...I just made an observation, that could possibly be attributed to any of the above problems. The old, tired, worn out 351M would get 10mpg city and 14mpg hwy...the new 400 get's about 7 and 9.5. I just really didn't expect such a big drop in mpg's going from a bad engine to a good one.
All that said, this was all tried with a Holley Mechanical fuel pump, an O'Reilly's house brand mech. pump, and an AutoZone chinese piece of crap mech pump. The problems seemed to get better with the Holley pump, but was still there...and that pump was trashed when it was accidentally ran over.
I also tried an electric fuel pump rated at 4-7psi and problems 1,2 and 5 were worse. Problem 3 was eliminated. And problem 4 maintained.
Again, thanks for any info.
1) The biggest problem of all is, there seems to be a backfiring issue. It's not a consistent problem, but it seems to happen most often when I let off the gas to coast or slow down, then when I go to get back on the throttle I get pop/backfire and then it'll accelerate. It also seems to happen at shift changes as well. It's worse when the vehicle is cold, but as I said...the problem is not consistent at all.
2) When traveling at sub 35mph speeds, and I go to give it a little bit of gas, it will sputter/stutter a little bit and then resume properly...not that big of a deal...just more of an annoyance.
3) There have been 5 times now in about 500 miles of driving where I will start the vehicle and start driving and after a few hundred feet the vehicle will die. It's almost like it's using whatever fuel is in the bowl, and then like there was no fuel in the outlet line from the fuel pump.
4) I've noticed a new vibration...or wobble rather...that wasn't there with the old engine between 60-70mph. Not sure if this is engine related, but it wasn't there until the swap.
5) Now I know these things aren't gas sippers, and I'm not complaining...I just made an observation, that could possibly be attributed to any of the above problems. The old, tired, worn out 351M would get 10mpg city and 14mpg hwy...the new 400 get's about 7 and 9.5. I just really didn't expect such a big drop in mpg's going from a bad engine to a good one.
All that said, this was all tried with a Holley Mechanical fuel pump, an O'Reilly's house brand mech. pump, and an AutoZone chinese piece of crap mech pump. The problems seemed to get better with the Holley pump, but was still there...and that pump was trashed when it was accidentally ran over.
I also tried an electric fuel pump rated at 4-7psi and problems 1,2 and 5 were worse. Problem 3 was eliminated. And problem 4 maintained.
Again, thanks for any info.