VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 speed

Through a series of engine problems and events, I have wound up with a 261 engine from a 1958 truck. I drive my car daily except for winter when there is snow/salt on the road. I also make a few short trips. My Question is about highway speed. l have noticed that Gene and a few others mentioned that they drive at 70 mph on the interstate. My car is a power glide and am wondering if this is feasible in my car.

I have used a tach and GPS to check my RPM at different speeds. At 65 rpm the engine is turning about 3100 rpm. I might overthinking the whole thing, but what is your opinion on 70 mph on the highway. The engine has not been rebuilt but it is solid. No smoke but uses a little oil.(mostly leaks)

All help and advice appreciated, Pete

Your engine should be turning over 2760 RPM at 60 with the Power Glide 3.55 gears and 6.70X15 tires.
At 70 MPH 3220 RPM. If you are running the original Power Glide raise those numbers about 2 percent for torque converter slippage.
In my thoughts 3200 RPM is a safe engine speed for a 235 orr 261 engine in good condition aluminum piston full presure oiling engine.
Yrs, I drive my 1950 Poer glide with original cast iron pistons and dipper rod lubrication (on the interstatess) between 65 t0 70 MPH.....and the engine has over 50,000 miles and never been apart.
Also dove my '39 at those speeds with the 3.73 gears, 6.00X16 tires, aluminum pstons and dipper rods.

Maybe I am missing something. Did you change the rear axle ratio when you installed the 1954 engine and transmission? Based on the specifications for a 1951 car with a 4.11 rear axle ratio, 60 mph is about 3100 rpm. Most people install the 3.55 rear that was used with the PowerGlide cars. With that ratio the engine should run at about 2900 rpm at 65.

i wonder if you actually have a 3.70 rear axle. That works out to about 3000 rpm at 65 mph.

i would not be too concerned about running the 261 at the same engine speed. While the engine speed will definitely hurt gas mileage it is a full pressure lubricated engine.

Actually I am more concerned about steering, suspension, and brakes driving these classic cars at 70 mph.

Thanks for the responses. I don't do a lot of interstate driving but when I do I like to stay out of the way. My spedo is 5 mph off. When it registers 70 I am really only doing 65. When driving on interstate etc. I try to keep the spedo between 70 and 75.

Again, thanks for the information, Pete