Vintage Mustang Forums banner

1 - 20 of 55 Posts

·
Registered
1970 Mustang Fastback
Joined
·
35 Posts
Discussion Starter #1
Hello,

New here to the classic muscle car scene. I was wondering what the general cruising speed is for a Ford Toploader.
What RPM is consider safe at x miles per hour when in 4th gear? What speed do you cruise at?
When driving anywhere above 55 mph, the car feels overloaded. I worry about wearing out the engine or transmission.
Any advice would be great, thanks! Learning as I go :)

Transmission Gear Ratio: 2.78 / Rear Axle Ratio: 2.79 / Tire Diameter: 24.17 / Wheels: 14x7
Engine is a 5.7L V8 347 Stroker if it helps.

749204
 

·
Premium Member
Joined
·
3,435 Posts
You're probably between 2800 and 3000 rpm at 70mph and well put-together engine should just be waking up there!
 

·
Registered
1970 Mustang Fastback
Joined
·
35 Posts
Discussion Starter #3
Thank you for the info, it's honestly hard to tell without a tachometer haha
 

·
Registered
Joined
·
4,084 Posts
I'm running a Toploader with 3.55 gears in the rear, and my cruising speed is 3400 rpm at 70 miles per hour. This is a 65 Mustang with a 289. A couple of years ago, I drove from Reno, NV to Bishop, CA doing 70 mph almost the whole way and got 21.5 mpg. At 3400 rpm, my engine hasn't even thought about any strain on the components.
 

·
Registered
1970 Mustang Fastback
Joined
·
35 Posts
Discussion Starter #5
That helps alot Fred! I guess there's really nothing to worry about then. I'll test her out more and see how she fares at different mph.
Close thread :)
 

·
Registered
1967 Mustang GT fastback
Joined
·
4,005 Posts
Problem is, we are all used to driving with silent overdrive geared modern cars. Old machines like our Mustangs ran at 2500-3500 RPM or more, all day going down the interstates. I still remember years ago hearing a 3.89 geared '66 Shelby on the highway at 70 mph and thinking that that old engine was working... Then I remembered it probably had a good couple thousand to go til redline so it was happy there, just nicely getting on the cam. That actually was our "normal" back in the day. And as long as regular maintenance was carried out on those engines, they loved it. We tend to think of 1500 RPM cruising along in 5th or 6th or 7th or however many gears your modern tranny has. But that's what it was like back then, and every once in a while a good Italian tune-up never hurt either!
 

·
Premium Member
Joined
·
13,083 Posts
Cruising @ 4,000 + rpm isn’t punishing, or wearing out, any FSB engine, it’s just exercise. I’ve taken numerous cross country trips in a variety of small block Mustangs and Shelbys. Many days of 14 hours behind the wheel. I can’t recall ever going under 4,000 rpm .....

Z
 

·
Registered
Joined
·
20,799 Posts
I recently read something by Billy Godbold who is chief engineer for Comp Cams about flat tappet failures. He said one of the reasons car manufactures made the switch to roller cams was due to high warranty claims on flat tappets. He said the big reason for the failures was due to a lack of RPM. He stated the car companies started using taller gears for improved fuel economy and the low RPM resulted in a lack of splash lubrication for the flat tappet cam.

Yeah I never thought twice at driving at 3500 RPM on the highway. It was normal.
 

·
Registered
Joined
·
1,554 Posts
My car has a 351C 2BBL, FMX and 3.50 gears. I've never had a tachometer in it. It easily cruizes all day and all night at 90 MPH.
 

·
Premium Member
Joined
·
11,039 Posts
It was also normal to have a near worn out engine at 60-80K miles:) Also like then it might take us 10+ years to get there.
Yes, it was normal for an engine to need an overhaul before reaching 100K miles but it was due to the oil that was available at the time. With modern oil that is no longer a problem.
That is the story I've read numerous times. YMMV.
 

·
Registered
Joined
·
9,916 Posts
Nice car!

FYI, I have a 1970 Mach 1 and it didn't come with a factory tach. I installed a reproduction hood tach. Back in the '70s, it was an over the counter part you could buy at the Ford dealer. Anyway, it's a bit expensive, but less than finding and buying a factory tach, and I really like mine.

749233
 

·
Registered
Joined
·
2,046 Posts
One reason I put an AOD in my car was that I intended to go to as many MCA shows as possible each year. I live in Canada so this meant a lot of long days driving for my wife and I behind the wheel.
Just one example, on a trip, like going to the show Savannah a few years ago, It is beyond imagination doing that in a car with the engine screaming at 3500 rpm all day, three days in a row. I would question anyone who says they are comfortable going that route.
My car was cammed and geared to do comfortable long legged trips, its 331 turns 1950 rpm at 70mph.
It only rarely drops into third only on some of the steepest grades in West Virginia all the while getting up to 24. mpg on the flat.
YMMV
 

·
Registered
Joined
·
20,799 Posts
Yes, it was normal for an engine to need an overhaul before reaching 100K miles but it was due to the oil that was available at the time. With modern oil that is no longer a problem.
That is the story I've read numerous times. YMMV.
Not to mention thicker piston rings with more tension and gas washing all the oil off the cylinder walls on cold starts with the choke on. Not to mention different manufacturing.
 

·
VMF Ambassador
Joined
·
6,536 Posts
I've got 3.25 gears out back and a Toploader. My cruising speed is somewhere between 80 and 90 MPH, which translates to about 3500-3700 RPM. No sweat and it's got plenty of juice left for passing at that RPM!
 

·
Just some guy
Joined
·
20,232 Posts
Kelly modestly leaves out that she's crossed the country like twice in that car at those speeds. Often packed solid with camping gear and such.
 

·
Registered
Joined
·
2,046 Posts
I've got 3.25 gears out back and a Toploader. My cruising speed is somewhere between 80 and 90 MPH, which translates to about 3500-3700 RPM. No sweat and it's got plenty of juice left for passing at that RPM!
To me cruising and 80-90 mph should not be used in the same sentence.
Just out of curiosity why does one need to pass another vehicle going 80-90,
in a car you yourself said, is over 50 years old that does not stop well.... seems more like a death wish.
Sorry, I just do not understand that type of mentality.
 
1 - 20 of 55 Posts
Top