Idle tuning LS7 with 239-251/570/106 ??

[Bruce Melton]

This is a LS7 short block with ported L92 heads, L76 intake, SVO42s, 90mm TB and this Grand AM cam which is 239-251/570/106 in a 99 C5. Startup went ok but it is winter in WI. Not really safe to AutoVE much yet so trying to nail down the idle. This large cam is test for me as the owner who is a NASCAR engine builder is dying to put a carb and distributor on this thing. Constant banter that I will never get it right.
Anyway, I updated to 02 Z06 OS and made educated guesses on startup tune which worked out ok.
Using BIDI found the car wants to idle @ 16 deg timing and indicated ~16 AFR. Not 12 deg or 18 deg but only @16 deg. It snorts happily there but if it varies much, it goes nuts. My 402 likes to idle @~25 deg which is more normal to me.
The problem is with B5932&3 blanked out 400>1200 @ 16 deg, how do I transition the table out to higher rpms? Granted fuel is not right yet, but if the car settles into idle @ 16 (@1000rpm) it is tough to transition out and takes some time to settle in. Of course if it gets a whiff of more timing, it surges badly.
Can someone help me before he orders the f'ing Holley?
Thanks,
Bruce

Description<o:p></o:p>
This hydraulic roller camshaft is designed by the GM Racing Division for road racing applications in the Grand-Am series. Serious duration and lift will require that the piston to valve clearance be checked as well as major PCM modifications. For best torque, install the intake centerline 105 for best power install at 107. GM recommends lightweight valves and valve springs from the 2002-03 LS6 engine for use with this camshaft.<o:p></o:p>
<o:p> </o:p>
Note: When installing this camshaft, it is critical that you use the point of maximum lift on the intake lobe. This is not a symmetrical lobe design!<o:p></o:p>
<o:p> </o:p>
Specifications<o:p></o:p>
SDPC Part Number: 88958606<o:p></o:p>
Manufacturer: GM Performance Parts<o:p></o:p>
Advertised Duration Int. : 294<o:p></o:p>
Advertised Duration Exh. : 306<o:p></o:p>
Camshaft Duration @ 0.050" I/E : 239 / 251<o:p></o:p>
Camshaft Lift I/E : 0.570 / 0.570<o:p></o:p>
Lobe Seperation Angle : 106<o:p></o:p>
RPM Range : 4000-7000<o:p></o:p>
Camshaft Type : Hydraulic Roller<o:p></o:p>
<o:p> </o:p>
239-251/570/106<o:p></o:p>

[TAQuickness]

Just covering what you know...

Your 16* is in your base timing in gear. You can get stationary idle worked out here. As soon as your non-idle conditions/enablers are met, you will transistion out of idle (base spark in gear) into the octane tables (assume High octane OLSD for now).

For a non idle condition, it's entirely possible you need a much different spark curve for desired operation.

So simply put, dial in stationary idle. Dial in the off idle low load/RPM. When satisfied with both, use the cracker/follower decay rates to ease the transistion between spark tables. It may help to also blend/smooth your octane table to help you transision back to idle.

How's your low load/RPM (drive thru a school zone in gear) working out with that cam?

[ringram]

Tell us how the power goes with that cam on the LS7, it might be a good L92 cam too!

[Bruce Melton]

Thanks guys.
I will try the suggestions. Problem is car is 150 miles from here and the weather is not friendly for on the road tuning. I think I can get it here and have more ongoing access.

The cam, I think will be fine. When running with best guess startup tune, it was quite docile on the road even below 2000 rpm in gear. It however, is anything but stealth.