Drawbacks might be a little less torque at lower rpm's. This header is designed for a motor that can flow very well upwards of 11,000 rpm. Probably would not be good for track/roadracing/autocross. Best for drag racing. Being 1.8 won't make a huge difference, but if the head isn't professionally done to flow over 280cfm, then it will. The lower flowing head you have the more displacement you would need to keep up. I will measure today but I beleive it is a 3 bolt flange 3" collector.