Hey guys, its been a while since my last post but I'm in serious need of any help anyone can lend. I'm at whits end with this car and just want to resolve these issues and be done with it! I'm turning to the internet's Mopar gurus on this hoping you have some insight.
I have a 410" magnum smallblock in my car. Early this year I decided to go with a new top end and fuel system to add some power and resolve a few issues with my mechanical pump. The car used to pop/back fire in higher rpm (anything above 4k rpm) and I had assumed it was not receiving enough fuel from my spent old mech pump. The one day it went to the track the car would run out of fuel before the 1/8th and coast the rest of the track.
So as for this years set up...I bought some IndyX heads from IMM engine and they CNC'd them for me. I also purchased one of the cams he suggested to go with the heads. ( 285 int / 289 exh, dur @ .50: 241 / 245 108 LSA, .582 / .571 lift). I'm running 1.6 rockers.
The fuel system is now the Aeromotive Phantom 200, in-tank electric pump. All plumbed with 1/2" line to the regulator and 3/8" to carb, and running around 8psi as per Aeromotive.
The carb is a holley 750 and was jetted up to 76/80 based on my old setup of factory magnum heads and a mechanical pump. jetted this way for break-in on the new cm.
The car fired right up and had no problems, until going over 4k rpm in first gear/3k rpm in 2nd or 3rd gear just like before!
I installed an air/fuel gauge with a wideband o2 sensor in the exhaust to get an idea of what was going on in case it was a fuel issue. The car was very rich, off the scale at any load at 10.0:1 and idling around 12.0:1.
I contacted Rev-N-Nator about the problem and they concluded there was likely an issue with my ignition box. I've had the box for about 2 years so it was one thing that was carried over. I sent my box out and they sent me a new one (never specified if the old box did indeed have an issue or not). As for the remainder of my ignition system I have the MSD blaster 2 coil they commended as well as the Mopar Performance distributor they used to recommend that is now discontinued (PN 249776 - Elect ignition, mech advance only).
The new box was installed as per their instruction, the timing rechecked and running around 31 degrees. It was backed down a few degrees (33) from the first box I had. With the new box installed the car still keeps popping/backfiring/refusing to rev, maybe even worse than before.
I've jetted the carb down from 76 in the primaries to 73 (still rich) and now to the 71 the carb came with and still only marginally better and very very rich (idling at 12.x:1).
One last thing to note, the car has been run strictly on 112 octane since the new top end. On the old setup it was also run mostly on 112. I had some detonation issues with the original 408 I had in the car that ate a piston on 93.
The car fires right up and runs very smooth until that 4k /3k rpm area then it all just falls apart. This has been very frustrating and I am open to any suggestions at this point as the car just refuses to want to run properly.:banghead:
I have a 410" magnum smallblock in my car. Early this year I decided to go with a new top end and fuel system to add some power and resolve a few issues with my mechanical pump. The car used to pop/back fire in higher rpm (anything above 4k rpm) and I had assumed it was not receiving enough fuel from my spent old mech pump. The one day it went to the track the car would run out of fuel before the 1/8th and coast the rest of the track.
So as for this years set up...I bought some IndyX heads from IMM engine and they CNC'd them for me. I also purchased one of the cams he suggested to go with the heads. ( 285 int / 289 exh, dur @ .50: 241 / 245 108 LSA, .582 / .571 lift). I'm running 1.6 rockers.
The fuel system is now the Aeromotive Phantom 200, in-tank electric pump. All plumbed with 1/2" line to the regulator and 3/8" to carb, and running around 8psi as per Aeromotive.
The carb is a holley 750 and was jetted up to 76/80 based on my old setup of factory magnum heads and a mechanical pump. jetted this way for break-in on the new cm.
The car fired right up and had no problems, until going over 4k rpm in first gear/3k rpm in 2nd or 3rd gear just like before!
I installed an air/fuel gauge with a wideband o2 sensor in the exhaust to get an idea of what was going on in case it was a fuel issue. The car was very rich, off the scale at any load at 10.0:1 and idling around 12.0:1.
I contacted Rev-N-Nator about the problem and they concluded there was likely an issue with my ignition box. I've had the box for about 2 years so it was one thing that was carried over. I sent my box out and they sent me a new one (never specified if the old box did indeed have an issue or not). As for the remainder of my ignition system I have the MSD blaster 2 coil they commended as well as the Mopar Performance distributor they used to recommend that is now discontinued (PN 249776 - Elect ignition, mech advance only).
The new box was installed as per their instruction, the timing rechecked and running around 31 degrees. It was backed down a few degrees (33) from the first box I had. With the new box installed the car still keeps popping/backfiring/refusing to rev, maybe even worse than before.
I've jetted the carb down from 76 in the primaries to 73 (still rich) and now to the 71 the carb came with and still only marginally better and very very rich (idling at 12.x:1).
One last thing to note, the car has been run strictly on 112 octane since the new top end. On the old setup it was also run mostly on 112. I had some detonation issues with the original 408 I had in the car that ate a piston on 93.
The car fires right up and runs very smooth until that 4k /3k rpm area then it all just falls apart. This has been very frustrating and I am open to any suggestions at this point as the car just refuses to want to run properly.:banghead:
