So engine was built for my father, it’s going in. 67 cutlass and I’m worried about have enough vacuum for the brakes and im going to run a th400 and would like it to have trans shift automatically if i want to and not have to have a manual valve body. Transmission guy tells me I need at 12” of vacuum. Any ideas here guys? I can run it on engine stand if need be but never hurts to ask first right!

 

Based on the testing we’ve done, you’ll be fine. Mainly due to the cubic inches. That makes the cam seem more mild than it is. Just tweak idle speed and idle timing and you should be fine.

 

Thanks Jerry.

 

I have built lots of transmissions for engines with less than 12 inches of vacuum. No big deal.

Use an adjustable vacuum modulator if you want to play around with fine tuning shift points. Keep in mind, you can only move the shift points up or down 2-4 mph.