6600 rpm breaking up
Posted: Sat Jun 09, 2012 11:24 am
Well I have been fighting this for a couple of years now and have no other parts to toss at it or tweaks I can read to try and change stuff. Just finally trying to get others thoughts in case I am missing something.
Car~
1993 Mustang Origonal 4cyl car
Engine~
347 9.61
Quickfuel 750 carb (Did it with a Holley 650)
Ported Vic Jr intake (never changed it)
AFR 185 heads stock out of the box (springs have been changed to two different cams)
Magnafuel fuel system -10 to pump -8 to regulator (2) -8 to carb ( Had a lesser fuel system on it last year)
1" HVC spacer or 2" hvc spacer
K&N filter on or off with an open K&N top
1 7/8 Accufab long tubes to 3" collector to 3" x-pipe and Magnaflow mufflers (had smaller headers on it until last year with flowmasters)
N-91 cam (had a comp cam before)
Smith brothers 5/16 push rods (had comp cams with the older cam)
Stock brand new FORD oem lifters (with the old cam had a set of modified stock oem lifters from Joe Sherman racing)
Spring pressure right now is 172 on the seat 427 open @ 600 lift (had lesser with Comp cam then we upped them for the comp cam no change)
Instal heights range from 1.84 - 1.845
MSD 7530 (Had a 6al)
MSD hvc coil (Had a Blaster)
Ranged from NGK bkr5e and 6 gaped any were from 50 to 25
Two different converters
Taylor 409 wires (I don't think I ever changed them since build)
92/93 octane gas
Msd goes directly to the battery, car has all welding wire powers and grounds with multiple grounds even the heads grounded.
Two years ago the wide band showed no change and neither did the fuel pressure so that had me stumped. I changed cams and when it did it it showed the fuel pressure drop and the car go lean. So I finally put a good fuel system on it but it didn't change it and the wide band doesn't change when it does it. It does it in all three gears also..
The car runs great it has gone 10.66 to the 1100' mark and me having to drive it the rest of the way out. It has a 28" tall tire and a 4.56 gear in it, I understand I could change the gear and make a pass but if I can figure out this issue that shouldn't be happening this combo has a little more in it.
So a quick recap everything has been changed minus the intake manifold and the plug wires, who did the port work on the intake manifold is unknown but doesn't look crazy. I did fight a vacuum leak for ever on a port the had below the carb and had a gauge in it and I just plugged it. They also have a plug in the bottom of the manifold and one in each rear water port. It did it with two different cams and different spring rates and different lifters so I have kind of ruled out valve float?
Thanks for the time in advance an if I need to list something else please let me know.
Car~
1993 Mustang Origonal 4cyl car
Engine~
347 9.61
Quickfuel 750 carb (Did it with a Holley 650)
Ported Vic Jr intake (never changed it)
AFR 185 heads stock out of the box (springs have been changed to two different cams)
Magnafuel fuel system -10 to pump -8 to regulator (2) -8 to carb ( Had a lesser fuel system on it last year)
1" HVC spacer or 2" hvc spacer
K&N filter on or off with an open K&N top
1 7/8 Accufab long tubes to 3" collector to 3" x-pipe and Magnaflow mufflers (had smaller headers on it until last year with flowmasters)
N-91 cam (had a comp cam before)
Smith brothers 5/16 push rods (had comp cams with the older cam)
Stock brand new FORD oem lifters (with the old cam had a set of modified stock oem lifters from Joe Sherman racing)
Spring pressure right now is 172 on the seat 427 open @ 600 lift (had lesser with Comp cam then we upped them for the comp cam no change)
Instal heights range from 1.84 - 1.845
MSD 7530 (Had a 6al)
MSD hvc coil (Had a Blaster)
Ranged from NGK bkr5e and 6 gaped any were from 50 to 25
Two different converters
Taylor 409 wires (I don't think I ever changed them since build)
92/93 octane gas
Msd goes directly to the battery, car has all welding wire powers and grounds with multiple grounds even the heads grounded.
Two years ago the wide band showed no change and neither did the fuel pressure so that had me stumped. I changed cams and when it did it it showed the fuel pressure drop and the car go lean. So I finally put a good fuel system on it but it didn't change it and the wide band doesn't change when it does it. It does it in all three gears also..
The car runs great it has gone 10.66 to the 1100' mark and me having to drive it the rest of the way out. It has a 28" tall tire and a 4.56 gear in it, I understand I could change the gear and make a pass but if I can figure out this issue that shouldn't be happening this combo has a little more in it.
So a quick recap everything has been changed minus the intake manifold and the plug wires, who did the port work on the intake manifold is unknown but doesn't look crazy. I did fight a vacuum leak for ever on a port the had below the carb and had a gauge in it and I just plugged it. They also have a plug in the bottom of the manifold and one in each rear water port. It did it with two different cams and different spring rates and different lifters so I have kind of ruled out valve float?
Thanks for the time in advance an if I need to list something else please let me know.