Originally Posted by 0010

For 17.5 gearing, somewhere in the 4.2 - 4.5 range depending on the size of your running space. I am running a Trinity D3.5 17.5 with timing advanced all the way to the stop on a carpet track that is about 70x40 feet and running a 4.42 FDR. Temps after 5-6 minute race is staying around 105 degrees, but I am running a fan. The car jumps off the line and is pretty quick in the space. If you are running in a larger area, you could go a little lower on the FDR. Or, if you don't crank your timing up, you could run a lot lower FDR. Its up to you how you want the car to behave, but for me, I had too much torque with the lower timing setting.

Whatever you do, keep a temp gun handy and check after a minute or so after every ratio change or timing change. Keep it under 160 degrees and you should be fine.