I have a small issue with my 499 stroker motor which has been a little irksome. I am going to get it professionaly tuned but for right now, I'd just like to get the bugs out of the motor so I can break the car in soon.
The issue I am having is the motor, after it warms up, is that it doesn not want to idle back down all the way. If I blip the throttle or rev her up, the motor tends to setttle back down to about 850 RPM where I have the curb idle set to around 750 RPM (out of gear - auto). This problem was MUCH worse before as I had the accel pump arm a bit to tight which was holding the throttle plates from returning all the way. I adjusted this where it doesn't happen as badly but not so much where the engine goes lean when you blip the throttle. This seems to be adjusted properly now.
I also shortened the return springs a tad so they pull tighter on the lever but this issue still happens just a little where it seems to not want to return to fully closed....I have also verified the butterflies aren't scrubbing on the intake manifold that I can see/feel.
This wouldn't be such a huge issue except that my motor tends to "run-on" or diesel a cycle or two if cut off anywhere above 750-800RPM out of gear. The motor has only had maybe 5 hours of runtime since being built so I don't think it's carbon build-up. I am guessing maybe the motor is tending to do this becuase it's high compression (I am running 93 octane).
Here are the specs on what I am dealing with:
- Holley 4150 elect choke
- 400>>499 4.15" stoker
- Eddy Alum Heads OOB 88cc
- Mopar elec ign "chrome box"
- 16 deg adv base timing @ idle
- motor is 10.4:1 static and 8.35:1 dynamic compression ratio
Do you guys have any idea what I could do to stop this "run-on" and/or fix this throttle return issue? I am guessing they are kind of intertwined but I am a bit miffed as to what to do.
I want my motor to cut off and not sound like crap when I cut er off and I want my idle to settle back to the 750 RPM out of gear.
Any help or ideas are appreciated!