Looking for a couple of tips to help tune my 1970 SS 396 with TH400. The engine is basically stock (402 with .030) except for the comp cams 224x234, .51x.52 bumpstick. I would like to tune the timing and idle mixture using the "vacuum method" and I have a couple of questions.

1. Do I connect the vac gauge to manifold vac?
2. How much vac should I be pulling?
3. If I time it for max vac will it ping?
4. How far should I turn the idle mixture screws (QJet) each time and should I do one side first and then the other or both at the same time?
5. How much should the vac vary during this procedure?
6. How low should I set the idle during this procedure?
7. With an automatic do I have to do the adjusting with it in gear or can I do it in park as long as I am in the proper rpm range that it will be running at?

Thanks in advance. Kevin

1. yes
2. 12 - 17 in
3. Not unless you advance the timing
4. both about 1/4 turn then let it settle out
5. a couple of inches
6. 600 - 800 rpm
7. you can adjust it in park and then reset idle after you put into gear.

[This message has been edited by Tom Kordick (edited 09-16-99).]

Thanks Tom, but one more question...When I adjust the timing for maximum vacuum, do I do this with the vacuum advance connected or disconected? Kevin

either way just be consistent on how you do it. It may be easier to notice the changes with it disconnected.

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Ok, thanks, I'll fool around with it this weekend. I've been putting this car together for so long, this is the fun part. Kevin