Lowered the compression from 11-1 to 9-1

Before I had 18 on the vacuum side, now i only get around 11-12, my car is surging, or hunting when started and I can not find a vacuum leak anywhere.

If I lower the compression, do i get less vacuum?

 

i'm roughly 9:1 and get 20 in/hg at idle ... and i did when i was 9.5:1, 10:1, and ~11:1

should pull the same vacuum, or at least damn close regardless of your compression.

I do remember that when i went from 11:1 to my current motor, the car surged and had 10 in/hg of vacuum ... messed with the map a bit and vacuum was fine.

 

I wonder if its my MAP then, I installed a new TB and had to clock the TPS a few degrees and then go into the ems and make up for the difference in voltages

 

That could be it with the MAP. Also if one of your cylinders are not firing, this would cause less vacuum.

But since your motor is searching, loping, not idleing smoothly, then I guess a sensor is whack or there is a leak somewhere. G/L