Headers vs 340 manifolds
This might clear up the 3/4 race history:
""The original 3/4 race cams are the forerunners of today’s street-performance grinds.
The term likely originated in the ‘50s as the burgeoning hot-rod industry was modifying Ford Flatheads to drag race on airport runways and attempt top-speed runs on dry lake beds. The legendary Ed Winfield was one the early pioneers in grinding camshafts with more aggressive lobe profiles, and the cams were often labeled as full race for promotional purposes.
“And then some guys wanted a milder cam that could also be used on the street, so they called it a three-quarter race cam because it didn’t have as much duration and lift,” explains John MacKichan of the
Speedway Motors Museum of American Speed in Lincoln, Nebraska.""
https://www.enginelabs.com/engine-t...m likely originated in,runs on dry lake beds.