speedometer difference

[84step]

I have just been wondering this for a while but I bought my truck and the guy told me that the previous owner had swapped out the 305 for a 350 the speedometer only goes up to 140km/h I was wondering what the difference on the tach is in relation to speed, o yeah i have 15" rallys just incase that matters.

[73chevyman]

wow you lost me here???? well tach is telling you how many revolutions your motor is going at what ever speed your going. the speed ometer is just to simplify things for the moderen man. but todays aspect of it is to get your rpm's lower at 55 normally 55mph is about 2600 rpm's. it's all how you look at it think what i wrote probably don't make since