Do you set idle timing to what ever produces the most vacuum?

 

Ideally that would be fine to do. But you will loose under speed spark correction by doing that. Fine best vac and wind it back enough to allow spark control to work

 

What is your set up?

 

Under spark correction?


408ci
AFR 225
235/239 113
LS6 intake
1.75" headers

 

I would find the best spark position, then take out 5 degrees and give it to
the underspeed table like macca says. That table is messed up in some years,
check it and make sure it's not set to "give up" at high underspeed.

 

i have a 408 with a 236/244 @114 same headers, fast intake...

my spark cells and around it are at 29 and the over/under and correction tables are stock. make sure your ve is spot on, your timing table is smooth and if you are trying to run closed loop expect it to over-fuel at idle. i run open loop only.

 

No. You set advance a ~5 degrees less than maximum vacuum (or lowest kPA) to give the idle spark over/under speed correction tables enough range to do their job.

When the idle spark is set at maximum vacuum (or lowest kPa) it is hyper-sensitive to any change in fuel/air/spark which makes it difficult to achieve a smooth idle.

 

This is what I do

 

Good ole spark correction!

I found that my car made the mount vacuum with stock idle spark tables.

So it deffinetley varries

236/240 cam