Hi, dose any one knows why after converting a standard 5.0 to a H) 5.0, the cars is runnubg to rich and not holding idle.
We would need way more info than that to accurately help you.
Without more info I can only offer basic troubleshooting advice and questions. What was involved in the conversion (what HO parts did you use, including ECM type/tag)? Did you re-route the plug wires to the HO firing order? You should have. Did you re-route the injector harness? You should NOT have. If using a speed-density EEC, did you connect the vacuum line to the MAP sensor on the firewall? If using mass-air, did you disconnect and plug that vacuum line, leaving the vacuum port on the MAP sensor open to the atmosphere? And finally, have you pulled trouble codes from the ECM? They would point you in the right direction.
Fuel pressure regulator any good?
I had a similar issue, but mine ran fine, just rich, even with a bunch of mods. how I fixed it was to put an Adjustable fuel pressure regulator on it... still runs a but rich but not bad.... Gotta get it back on the Dyno and dial it in better.
your timing will need to be adjusted as well.