Takid455
06-04-2012, 05:31 AM
Running a Holley Projection 4i (not 4Di), yes I know is old. Having an issue with the mixture which is causing very poor running conditions.
Known:
'78 T/A 455 (approx 540 HP), T56 (0.50 6th), 3.73
14 psi going into regulator measured approx 8" before.
Have not measured return line pressure nor had the ability to monitor pressure while driving. Elec gauges can be ordered if need.
feed & return lines both 3/8"
Running electric in-tank pump (Typ late model GM style w/ bucket)
Temp sender is working. tested by unplugging when warm and mixture went super rich and rough running.
have piggy back Holley O2 unit installed, but ground so it acts as a tuning aid. LED is on during the 'problem' periods indicating a rich mixture. Had it hooked up and unplugged b/c I had an issue and though the unit was wacky. Observing now, that the unit may not be the issue.
After sitting 1 week, car starts right up and idles around 800 rpm.
Take car out for drive, approx 45min country road and highway varying RPM w/ no issues. It does seem to be a little rich based on the fuel consumption. Slight hesitation during abrupt acceleration from say 2200 rpm cruise. Accelerations OK once initial transition is past.
Here is the head scratcher.
Since I am breaking in the rear end gears, I need to do a few heat cycles, no issues there. The problem occurs when I go out for round 2 say 1 hr or so later. Car performs like above for say 10 min then as soon as load is applied or increased throttle during 3rd gear or higher, I get a shaky and some stumbling followed by a huge BOOM in the exhaust. Sounds like a 12 gauge going off.
I havent fine tuned the Power 1 & 2 settings but have them at mid way on the adjustment. While this needs to be done, the bigger concern is the consistency and why the 2nd outing yields troubles?
Temp is 180-200 F. it was towards the higher side on the 2nd run.
Thoughts concerning this and only this system appreciated. Not looking to change unless it can be done w/ minimal surgery as the wiring and installation is all completed.
Who is experienced w/ this system.
Known:
'78 T/A 455 (approx 540 HP), T56 (0.50 6th), 3.73
14 psi going into regulator measured approx 8" before.
Have not measured return line pressure nor had the ability to monitor pressure while driving. Elec gauges can be ordered if need.
feed & return lines both 3/8"
Running electric in-tank pump (Typ late model GM style w/ bucket)
Temp sender is working. tested by unplugging when warm and mixture went super rich and rough running.
have piggy back Holley O2 unit installed, but ground so it acts as a tuning aid. LED is on during the 'problem' periods indicating a rich mixture. Had it hooked up and unplugged b/c I had an issue and though the unit was wacky. Observing now, that the unit may not be the issue.
After sitting 1 week, car starts right up and idles around 800 rpm.
Take car out for drive, approx 45min country road and highway varying RPM w/ no issues. It does seem to be a little rich based on the fuel consumption. Slight hesitation during abrupt acceleration from say 2200 rpm cruise. Accelerations OK once initial transition is past.
Here is the head scratcher.
Since I am breaking in the rear end gears, I need to do a few heat cycles, no issues there. The problem occurs when I go out for round 2 say 1 hr or so later. Car performs like above for say 10 min then as soon as load is applied or increased throttle during 3rd gear or higher, I get a shaky and some stumbling followed by a huge BOOM in the exhaust. Sounds like a 12 gauge going off.
I havent fine tuned the Power 1 & 2 settings but have them at mid way on the adjustment. While this needs to be done, the bigger concern is the consistency and why the 2nd outing yields troubles?
Temp is 180-200 F. it was towards the higher side on the 2nd run.
Thoughts concerning this and only this system appreciated. Not looking to change unless it can be done w/ minimal surgery as the wiring and installation is all completed.
Who is experienced w/ this system.