I'm running a Rover V8 with an Edelbrock performer dual plane manifold and 500cfm carb. Got a best time of 15.2 at the strip. Tried putting in a 1" open carb spacer to see if it did anything. Ended up with a 15.1, but that might not have anything to do with the spacer - I'd done a bunch of other things too. At the weekend I was getting 15.3/15.4s. So I thought - what would happen if I took the spacer off? I did this (and nothing else) and was rewarded with two 16.4s! Ouch.
Put the spacer back on and I was down to the 15.3 area again. With the spacer on, there was a slight bod off the line and another flat spot in 3rd at the top end of the strip.
Since I've managed 15.2 before the spacer went on, I'm surprised it's hurt so much to take it off again. Anyone got any ideas? Would a 1" spacer affect ignition timing?