The Ford Barn - View Single Post - Want o go highway speeds ??? Need opinions.

drolston · 01-28-2019, 05:44 PM

Pushing that truck through the air at 60 mph takes a certain amount of horsepower, regardless of what rpm the rear end dictates for that speed. The amount of heat generated by the engine at a given horsepower will vary a little with the rpm at which that horsepower is being delivered, based on the engine efficiency at a particular rpm. With the 4.11 gears normal for that truck, you are probably well over 3,000 rpm. With 3.25 gears the rpm will be down to maybe 2,500. The fan will be drawing less horsepower and the engine may be a bit more efficient at that rpm, but I doubt it will cure overheating.

Let's rule our a few things:
1) Water hoses not swollen or crimped
2) Take out the thermostats and try it. Maybe one or both are not opening properly.
3) Does your truck overheat sitting at idle, on a hot day? If so, check for retarded timing
4) Have you checked the water pumps; vanes intact and in good shape
5) Exhaust not restricted; crimped pipe or choked muffler?
6) After a hard run, check spark plugs to too-lean condition (white powder versus toast color)

01-28-2019, 05:44 PM	#3
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: Want o go highway speeds ??? Need opinions. Pushing that truck through the air at 60 mph takes a certain amount of horsepower, regardless of what rpm the rear end dictates for that speed. The amount of heat generated by the engine at a given horsepower will vary a little with the rpm at which that horsepower is being delivered, based on the engine efficiency at a particular rpm. With the 4.11 gears normal for that truck, you are probably well over 3,000 rpm. With 3.25 gears the rpm will be down to maybe 2,500. The fan will be drawing less horsepower and the engine may be a bit more efficient at that rpm, but I doubt it will cure overheating. Let's rule our a few things: 1) Water hoses not swollen or crimped 2) Take out the thermostats and try it. Maybe one or both are not opening properly. 3) Does your truck overheat sitting at idle, on a hot day? If so, check for retarded timing 4) Have you checked the water pumps; vanes intact and in good shape 5) Exhaust not restricted; crimped pipe or choked muffler? 6) After a hard run, check spark plugs to too-lean condition (white powder versus toast color)