Danger over 55? Superstition or Not?

[BJH324JH]

No, not your age. I mean 55 mph. Is driving over 55 mph too much for the G54B engine to handle or is this an old wives tale? Interestingly, the speedometer on these trucks has 55 color coded in orange to perhaps indicate "dangerous speed"? Anyone know if driving over 55 mph is something the G54B engine can safely do without killing itself?

[FMS88]

A properly tuned G54b and a well maintained truck should have no problem reaching and holding speeds much greater than 55. Depending on the final drive ratio, 70mph is around 3k rpm which the G54b can maintain for hours. The only problem can be hills which will tax its 90 horses as the grade increases.
The "55" speedo marking reflects the days after Nixon and Congress passed the 1974 Emergency Highway Energy Conservation Act in response to the oil embargo of 1973. The Act lowered highway speeds to 55mph. It was repealed in 1995. Here's the Wikipedia page:
https://en.wikipedia.org/wiki/Nation...imum_Speed_Law

[SubGothius]

Indeed, and in 1979 they passed another law requiring speedos to highlight the 55 and only show speeds up to a maximum of 85, tho' some mfrs. got cheeky with that and included add'l increment marks beyond 85, just unlabeled.

The freeway limit here is usually 75 outside of urban areas, and my '87 with a (Weber) carb'd G54B never had much trouble keeping up with the flow of traffic, tho' the terrain is fairly level, and I reckon steeper grades might present more of a challenge.

[BJH324JH]

Interesting, years I wondered and now I know. Thank you guys.