Tuning a big cam -- details
Tuning a big cam -- details I have a 230/236 .591/.601 114lsa in my 408. I've done the standard cam stuff -- bumped the idle, tweaked the airflow, IAC, base timing, etc., and have moved on to smoothness tuning. I've got it pretty smooth now, by changing the advance overspeed and underspeed corrections, and tweaking the adaptive idle code.
Everything works well except one thing (below) -- it starts and warms up decently, no idle hunting / surging, decels to idle well, etc.
Here's the thing I'm stuck on though: when going from park to reverse, I'm logging a huge dip in spark (like 15-20*) and of course, then the rpms dip 200-300 and engage the stall saver code. There is less severe but similiar behavior when going straight into drive (and that's the funny part... why is reverse worse??). I should mention that this *only* happens when moving the shifter and goes away quickly (in reverse, there are sometimes two dips, one right after the other, but in drive only one). I've looked at everything I can think of here, and have no answers.
Anyone have a clue?
Everything works well except one thing (below) -- it starts and warms up decently, no idle hunting / surging, decels to idle well, etc.
Here's the thing I'm stuck on though: when going from park to reverse, I'm logging a huge dip in spark (like 15-20*) and of course, then the rpms dip 200-300 and engage the stall saver code. There is less severe but similiar behavior when going straight into drive (and that's the funny part... why is reverse worse??). I should mention that this *only* happens when moving the shifter and goes away quickly (in reverse, there are sometimes two dips, one right after the other, but in drive only one). I've looked at everything I can think of here, and have no answers.
Anyone have a clue?
Try increasing your running airflow in drive. It should be a couple g/sec higher than in park. If your park/drive running airflow is even then your rpm will dip anytime you put the car into drive or reverse.
Check your park and drive spark tables. Are they similar for the above pertained g/cyl or are they very different? If the park table is much higher for the above pertained g/cyl then try increasing the drive spark table a touch in that area.
-Kevin
-Kevin
I wish I could help. (I will follow this thread tho) I spent 8 hrs SD tuning my car. In the 1st 7 hrs we got it very close to perfect doing what you did. In the last hr it all went to hell & we couldn't get it back. So I gave up & restored my MAF tune.
And now it's worse than ever. It even dies after I do a burnout at the track. So frustrating!
But I found the surging goes away completely if I unplug the IAC motor, so at least I have an ide what is wrong now. Good luck.
And now it's worse than ever. It even dies after I do a burnout at the track. So frustrating!
But I found the surging goes away completely if I unplug the IAC motor, so at least I have an ide what is wrong now. Good luck. 
