If the car and suspension is in good condition and the driver is competent the maximum safe traveling speed is whatever the car will do with the gas pedal shoved to the floorboard.

 

I can do 75 on the freeway without any issue. Good suspension, export brace and a Monte Carlo bar will make the car drive great.

 

You did not indicate transmission type ? I had a four speed in my 65 convertible and at 65MPH, the car was running very hard and it felt like i was going to tear it apart. I converted it to a T5 (5 Speed) and now going 75 or 80 is much smoother. Of course, i have gone through the suspension(Coil overs) , steering(Borgenson) and brakes(Disc brakes) on the car to support that speed as well.

so yes, 75MPH is not a problem but you will need to do some work to get there.

 

My 4 speed has no issue with 75+, OP what is your rear end gear ratio?

 

Dead stock C-Code with auto cruised at 80 no problem.

 

85. Some people went faster back then.

 

I dunno... 95 or so? 100? Whatever speed is allowable on the highway and won't get you thrown in jail?

Around here there's a few 80+ mph roads. There have been times when I've been "cruising" at 90 to keep up with traffic.

I don't like to really run the motor up past 3500 rpm for a super long period of time, but mostly just because it burns oil at those sustained rpms. Not like it's going to explode or anything at that rpm though.

 

These cars would happily drive at 100 mph with the A/C on full and the AM 5 watt radio speaker blaring in your ears, all day long. Or as long as the gas tank and your credit card held out. Of course at 39¢ a gallon it wasn't so expensive back then either.
Ford only voided the warranty if you were racing. They said nothing about sustained driving over 80 MPH, except for adding a couple PSI to the tires. They wouldn't have optioned "high speed capability" tires for these cars if the engine and chassis couldn't handle it safely and reliably. So if Ford's warranty penny pinchers weren't worried about high speeds, you shouldn't be either. FWIW, at around 80 MPH with my 3.00 rear end, my 289's doing a lousy 3000 rpm or so. Uses no coolant or oil either at those speeds. Heck, that's only just over twice the fast idle speed. I have an old Road and Track article from August 1965 where Henry Manney drove a dead stock 4 speed 289 coupe (with the new front disc brakes but not the handing package) that he borrowed off a Ford rep, all over Europe at around 80-90 mph including a stint going around the Targa Florio race track. Only thing he really complained about was not the engine which he loved for the "effortless poop at around 80 mph", it was the rather weak front shocks.
So, if your steering system's tight, suspension is good (esp. good shocks and an export brace), and properly aligned, not to mention good brakes, then put the hammer down and forget it.

 

I've found that 140 is fairly stable.

Oh, wait....you said stock.

55mph.

 

These cars are 50 years old. It's unlikely even "fully" restored will be as new mechanically. I had my 4 speed D code vert (sig car) brand new, had no hesitation driving 75-80. A Stang feeling unstable unsafe at that speed has something or several things wrong with alignment, suspension or steering.

Slim

 

These cars are 50 years old. It's unlikely even "fully" restored will be as new mechanically......"

Slim

Slim, generally speaking you are absolutely right. But a great percentage of the cars owned by the VFM'ers and other regional and national Mustang club'ers are maintained and restored to a higher standard than even factory new. Engine wise, and especially in the suspension and braking areas, our cars can now do easily what they were straining to accomplish those 50 years ago when I first fell for them head over heels.
O
Most of these recent postings are right on the money, the trend for overdrive drivetrains is just to help manufacturers meet mpg goals. Back in the day, cars or motorcycles got 5 speeds only if they didn't have any torque to speak of, and really needed the extra gears to keep the car in the narrow powerband . 90% of all cars and trucks in the 1960's with manual transmissions just had 3 speeds, and that worked out prettty well, because big American engines had plenty of torque.

But time moved on, and people under 55 are used to 2000 rpm cruising rpm and nothing will ever make (most of) them feel easy about cruising at 3,000 - 4,500 as SS2 alluded to. But these old cars are made to spend ALL DAY LONG at those rpm's. That is the comfort zone for the 289/302 engine and for some of us old dinosaurs as well.

If the vintage car is your daily driver, there is the valid mpg argument to be made for the T-5 and such in order to help the gas mileage. But few of us give a hoot or a holler about gas mileage. I think most people that go the T-5 route do it just to bring the rpm level down to what is the new normal. I got my '66 GT350 to cruise at just under 3,000 rpm @ 75 mph by putting in a 3.00:1 rear end and adding 80-100 HP to help acceleration. it was OK, but I really preferred having the stock 3.89 and having a cruising rpm of 3,900 rpm at 75 mph, or the 3.50:1 gearing of my HiPo which cruised @ 3,500 rpm at the same speed.

With the 3.00:1 gearing I missed the engine music of the 3.50 and 3.89 gearing, not to mention the better torque numbers of the higher rpm.

Z.

 

Safe top speed? Back off when the passenger compartment starts filling up with smoke from blow by from your old rings.

Your 289 is the last thing you'll need to worry about at high speed.

 

No faster than your guardian angel can fly....

 

God is my co-pilot (thank God)

Z

 

back when i first got my mustang, 75 was nothing to cruise at for extended periods of time. same with my falcons, all of them. as long as the car is in good overall condition, freeway speeds are no problem.

 

Speedo goes to 140 mph.
Say no more

Baxter

 

and theres a reason for that. mustang was meant to be driven fast

 

Speed

Like Kelly, I drive mine a lot and for long distances. Like Slim, I realize I'm driving 53 year old car. I have a lot of upgrades/improvements- export brace, GT front springs, BB rear springs, Koni shocks, 1" front sway bar, 22 gal tank, T-5, 3.25 rear and I try to level it around 75. It's still a C5 motor, even tho it was rebuilt in 08. There are times when 80-85 is keeping up with traffic, but why push it? After 389,000+miles, I plan on going over the 500K. I remember I'm the 2nd owner and do not remember the original miles, so I'd estimate it's already over 400K, if not a lot more. There is such a thing as metal fatigue, no matter how well it's maintained. How many of us have repaired cracked shock towers?

 

Like Kelly, I drive mine a lot and for long distances. Like Slim, I realize I'm driving 53 year old car. I have a lot of upgrades/improvements- export brace, GT front springs, BB rear springs, Koni shocks, 1" front sway bar, 22 gal tank, T-5, 3.25 rear and I try to level it around 75. It's still a C5 motor, even tho it was rebuilt in 08. There are times when 80-85 is keeping up with traffic, but why push it? After 389,000+miles, I plan on going over the 500K. I remember I'm the 2nd owner and do not remember the original miles, so I'd estimate it's already over 400K, if not a lot more. There is such a thing as metal fatigue, no matter how well it's maintained. How many of us have repaired cracked shock towers?

yes metal fatigue does happen. i havent repaired the shock towers in either my falcon or my mustang. i do however plan on reinforcing them at some point in time though. just like i plan on adding sub frame connectors, and tying them to the inner rocker panels as well as tying them together and creating a driveshaft loop. but those will only be done to stiffen the chassis as much as possible for better handling.

 

Cracked shock towers can happen on the 65/66 models of course, but are more common on the 67 and newer . The earlier cars had a more curved shock tower, which was resistant to cracking . The flat metal in the 67+ cars crack much more easily, which is why the reinforcement kits mainly exist for those years,

Z

 

The OP, hasn't been back since we told him to haul ace. Hope we didn't send him on a wild ride >

 

Not sure what my rear end gearing is but at 4000 RPM's or so, the motor is running pretty darn hard and i guess my point is I don't like beating the car up for long duration's of time. I have a rev limiter that stops it at 6000 RPM's and i did that once and felt pretty damn bad about it! I also worry about heat! Anything running that hard for that long is going to heat parts up.

Yes, I am use to everything having OD and I like things smoothness in cars. Last thing i want to do is rip the motor apart so call me conservative well once i get to 4000 to 5000 RPM's that is because i love getting there pretty fast.

 

Herein lies the problem with OP's original question. There are some Mustangs that would be unsafe at 25 mph with some people I know behind the wheel and some that would be safe at 120 mph, with others. What needs to be remembered is that when driving on a public highway is that the faster you go the LESS time you have to react to somebody else, who shouldn't even get behind the wheel of a riding lawnmower.

 

Generally speaking, the faster you go, the less chance you have to avoid a problem.

If it takes you a long time to stop, then you're driving too fast.

Otherwise, I think these cars are ok at 45mph. Faster if you're car is equipped to react to adversities in/on the road without flying off the side and into a house.

 

Back in my high school days I drove a 1971 fastback and a 1970 fasback. The 71 had a 302 2V and the 70 had a 351 Cleveland 2V. Both were bone stock.

I drove these cars hard through Oklahoma blizzards, ice storms and opressive, summer heat. I lived in a rural area with no traffic and typically cruised at 70 to 80. No problems at all.

On the contrary, my best friend in high school owned a 1968 Chevelle SS with a 396, 4-speed and 4.11 rear gear. Whenever we went somewhere, we took a Mustang. That Chevelle was a cool car, but sheesh, it used so much gas (premium gas of course) it was no fun! We drove it to school exactly once while we drove my Mustangs again and again. Not trying to dog bowtie cars here, but that Chevelle also broke down constantly. It was mostly a factory car, but by no means was it a reliable car. My friend maintained it very well, but something weird, like a rocker arm, was always breaking. Sure, it too would cruise at 80, but with a 4.11 gear, the engine was screaming and you could almost watch the gas gauge move.

 

I can solidly relate to that. I had my 65 FB A code, solid fun car I drove all year round, rain or snow. I got the itch and found a 71 Boss 351 with 3:91 gears. Built with Offy intake, 12:1 pistons, headers etc. It ruled at stop light to stop light. It also required premium with a Moroso Octane infusion, and drank a LOT of it. It blew header gaskets. The competition clutch and pressure plate required a strong left leg and took a lot of concentration to keep from chirping the tires taking off. It was great to cruise town with but for going to work, to school etc I found myself driving the 65 more and more. When the time came that I had to part with one or the other, I let the 71 go.

 

Much of the Interstate Highway System was built in the 1950's for 70 mph speed limits, and of course the Mustang was built to drive on them. I have driven mine on road trips at 75 mph for as much as 20 hours at a time (not a typo) with no problems.

 

Dobrostang, 2nd66 and I were all doing 90 about 6 weeks ago at a Watkins Glen charity event according to those two who were behind me. We couldn't pass that's the way we were lined up. We had to keep pace and keep in line.

Here's Dobrostang slowing up so the vette could keep up.

 

I'm surprised nobody has mentioned tires. The car could be completely restored and rock solid, but one bad tire will spell disaster. Quickly.

Start from what makes contact from the ground and work your way up to the steering wheel. Tires, entire steering system, suspension, brakes. 289s are tough little small blocks.

 

Nothing could be better said.

But tires continually get the short shrift. For 2 or 3 years I've been touting the superior handling qualities of the 15" Avon CR6ZZ tires. These tires will completely transform the way your car handles. But there doesn't seem to be anyone that thinks a $1,400 set of tires is worth what they can deliver. Somehow people who have NO problem spending thousands of dollars on drivetrains, and thousands of dollars on suspension and chassis upgrades, will balk at $1,400 for a set of tires. Even though tires are the only connection the drivetrain and the suspension has with the road, they still are minimized as to their importance. I've made around corners on the relatively narrow 215/60-15 Avons with no drama, only to see a couple guys following me (at the same speed) spin out with their 245's. ( yes, BFG RWL)

When it comes to having a rollicking good time with a vintage Mustang, there's absolutely no substitute for having sticky tires. Having all the fun I could handle, mine looked to last about 20,000 - 25,000 miles. Plenty for 4 to 5 years of great fun for most VFM'ers (Kelly_H excluded). But even she could get 2 years out of a set, easy.

CR6ZZ | Avon Motorsport

Available thru Rodger Krause Racing and other outlets

Roger Kraus Racing Ent., Inc.- Castro Valley, CA.


Z

 

Speed isnt the problem its the rate and cause of deceleration that hurts you. Your survival rate goes down as speed goes up, in theses cars you are in the crumple zone.

 

Speed isnt the problem its the rate and cause of deceleration that hurts you. Your survival rate goes down as speed goes up, in theses cars you are the crumple zone.

FIFY

 

SAFE is relative to suspension, brakes and most importantly tires.
Old dry rotted tires are not safe at any speed.