HP limit with 1-5/8 headers

1 5/8 verses larger tubes. With larger tubes, and 12 to compression, you arn't going see much, if any loss of low end torque. With the 1 5/8 tubes your upper end power will suffer . I agree with what has been said.. any serious street or strip performer will benefit with the larger tubes. I feel 1 5/8 is too small for hot well built 340/360. Torque (low RPM) motors (limited to 5500) will be fine with them. Stepped headers are good also but EXPENSIVE. 1 7/8 would make great hi-rpm power, 1 3/4 would work well also if you can find them for your chassis engine combo. Good luck and keep us posted. Terry.