Hello everybody,

I have a 1967 98 convertible. 425 Engine.
The German TÜV has written in the papers, the car runs about 118 mls. Is that realistic?

I think that is much too fast. The car is already nervous about 80mls.And the engine whines.

What you have for experience?
Did someone perhaps a list or something with the values?

Thank you.

 

These cars are not meant to be driven at continuous high rates of speed like the Autobahn stock. They can be modified to do it with a gear change and some suspension mods. They tend to float and wander as the speed gets higher than 80. Also tires need to be a consideration.

 

What is "mls" ? Miles [per hour]?

 

Maybe they mean 118mph is its top speed?. Sounds feasible for a bb Olds. I wouldn't want to be in the car if it was going that fast though.

In the Uk a blanket 70mph limit was introduces about 1967 I think. Did anything similar happen in the USA, or did some states impose one limit and others a different one (or none)?.
We had a blanket 50mph limit for a while after the 1973 oil price hike, and you guys had a 55 limit for many years, still in force in Texas in 1994 I believe.
But was there an blanket limit before then?.

German Autobahns had a somewhat justified reputation for being death roads with no speed limits.
Incidentally Northern Territory in Australia had no speed limit until this century, it also has a very high fatality rate for road accidents.....

Roger.

 

Back before the 70's states mandated their own speed limits. In the 70's during the oil embargo the US mandated a 55 mph speed limit and if they didn't abide they would cut off their hwy funding. Then later on it returned to the states mandating again. Now we have 80-85 mph areas including Texas.

 

On Interstate 10 in west Texas, December 2011.

 

I don't know if they still do, but for a while, Montana had no speed limit in the daytime. It was simply "reasonable and prudent."

 

@Oktania:Sorry, I thought you know the shortcut. But right, i mean miles per hour.

Many restrictions are correct. But many cars are being built faster than they are allowed to drive.
I want to know how fast can (theoretically) drive a 1967 Ninety Eight.

Oldcutless was right. At 80 miles per hour making driving uncomfortable. More I do not currently have dared.
But has anyone tested determines what is possible. Perhaps there it documents. And if someone has something, please give notice.

 

How many mph per 1000 rpm is a good figure to start from, simply extrapolate upward to the engines maximum speed.
If you Olds does 25mph per 1000 rpm and maxes out at 4500 rpm its theoretical maximum is 112.5mph.
Modern cars are very overgeared, my wife's diesel Peugeot theoretically is good for 140, it might crack a ton on a good day. Even my '87 Olds 88 has a theoretical 145 or so, I believe it could do 115 in good tune.
My fathers 5 speed Austin Maxi went faster in fourth than fifth, simply because the engine didn't have enough power to overcome wind resistance at higher speeds in fifth.

Roger.

 

Tire size and rear end ratio influence your RPM to speed ratio. For sheer engine speed rating, take your rpm change from 60 to 80, then add it to 80 to get what you'd have at 100. Then, you can keep on extrapolating. My 72 with a 2.73 gets 2500 at 70, 3500 at 100, so I estimate it would hit the yellow on the tach at 4500 at 130.

However, two things stop you. One, drag, and two, steering and suspension feel as the tires shake down the road and the car begins to lift. I don't want to drive my 72 faster than 100, it starts to wobble.

I would think, any stock gearing in a 98, with that block, assuming the steering and suspension are good, it ought to be able to hit 100. I would not keep it there long. 80mph, provided it doesn't overheat, should be fine to cruise at.

 

I've had mine up to 110.... once.... never again...

 

Agreed. If the machinery is all in very good/new condition, 100mph(& maybe a bit more) would be doable and not too uncomfortable.

??
I had my '68 with its worn suspension up to ~105-107 (indicated). It was out of legs at that point. I wouldn't have wanted to take a turn and it was a bit 'floaty', but on straight/level road, it wasn't scary.

Nope. Not any more. They phased it out (again) IIRC ~ 10 years ago. They brought it back ~ 20 years ago, but the concept of 'reasonable & prudent' is alien to too many people now. After too many out-of-staters being stupid and killing themselves & others (& therefore being threatened by the Fed$), they went back to posted limits.

 

I'll admit that I've never run an 1967 Olds 98 (or any Olds 98) up to maximum speed. But I have a hard time believing it was engineered to feel floaty above 80 mph! I suggest something's wrong with your car. Maybe it's as simple as the alignment being off or an air dam is missing. Maybe the springs have sagged to the point where the chassis geometry is not what it should be. Maybe the bushings or ball joints or other components are worn and sloppy. Maybe the shocks are worn or the wrong model. I really don't think it should start to float until well over 100, maybe even 120 mph. Having said that, if it feels unsafe, don't do it!


For the record, my '70 442 feels perfectly safe at 110; I don't take it any faster because the RPMs are too high. My '72 Cutlass started to float above 120 mph.

 

I read a story in a UK American car magazine about Mercedes Benz doing a lot of high speed testing in Montana when the limit was "Reasonable and prudent".
Apparently a highway patrol didn't like Mercedes cars and ticketed the whole fleet. Maybe an Urban Myth, but possible I guess.

Roger.

 

My 68 delta, I know not quite the same, got up to about 120 before I let off. Felt more stable the faster I went. Never tried to go faster than that Though

 

+1.

I like to avoid major legal expenses, so I never looked for the top speed, but when I had my '68 Delta, I had it up over 90 a number of times and it felt perfectly smooth and controlled.

If the entire suspension system is in good shape, the tires are good, and you have good shock absorbers (such as Bilsteins or Konis), 120 mph should be no problem on an Interstate or Autobahn, especially if you have a big block and a 2:56 rear.

There are published stories (I can't say whether they're true) about the state police regularly travelling at over 140 mph for extended period in high-geared '67 and '68 Deltas in one of the Western states (I forget which one - Oklahoma? Nebraska?) during the years their force used those cars.

- Eric

 

I wonder if even a tuned bbo made enough power to overcome drag at those speeds?.
And it would drain the fuel tank pretty quickly too.

Roger.

 

Another example of "How fast can you afford to go!"

In my young and stupid days I took a few cars well beyond their safe limits. I took my old '70 Camaro to 130MPH! I had a firm grip on the driver's seat with my... seat too!

80MPH should be a non-event in a '67 98 if everything is in decent condition.

 

Ha ha. I did the same thing in my Chevelle when I was 18 (in the RAIN!!).

Was driving on a patch of highway that was very unlikely to have any cops on it, and just put the pedal down.

At a calculated 130mph on the tachometer (the speedo never worked), the car felt like it was lifting up off the road, and the steering got very vague.

I VERY SLOWLY lifted my foot off the gas pedal while being VERY CAREFUL not to turn the wheel even the slightest amount...
... and I never did that again.

- Eric

 

Thank you for all impressions and opinions. Maybe I'll try. But only on a wide, empty street with an escort vehicle. Maybe.
I'll report back when I should have dared.

 

Check your rear-end ratio.

The available rear end ratios were 2.73, 3.08, 3.23, and 3.42.
3.08 was standard.
VERY few of these cars are found with ratios other than 2.73 or 3.08.

Your original tire size was 8.85x14, which is equivalent to 235/75R14, which has a circumference of 87.6", and turns 723 times in one mile.

So, at 60mph, if your car has the 2.73 rear, the engine should be turning 1,975 RPM.
With a 3.08 rear, it should turn 2,227 RPM.
With a 3.23 rear, it should turn 2,335 RPM.
With a 3.42 rear, it should turn 2,473 RPM.

Figuring a conservative redline of 4,500 RPM for a stock engine, that means,
Top speed with a 2.73 should be 152mph or 245kph.
Top speed with a 3.08 should be 135mph or 217kph.
Top speed with a 3.23 should be 129mph or 208kph.
Top speed with a 3.42 should be 121mph or 195kph.

So, to reiterate my two points:
1. If the engine is whining at 80mph there is a something wrong.
With the standard 3.08:1 rear end, it should be turning 2970 RPM, which is not a speed at which most would describe its sound as "whining."
Are you certain that your transmission is shifting into 3rd gear? In 2nd gear, with a 3.08 rear, your RPMs at 80mph should be 4,395 RPM, which would be whining.

2. These cars were designed to feel rock-steady on the open road and were routinely driven at 90 to 100mph in the western US when they were new, so if it feel "nervous," you need to check all of your front and rear-end bushings and links, your tires, your shock absorbers, and your wheel alignment.

Good luck!

- Eric

 

We're assuming we'll hear from either you or your next of kin.

 

@MDchanic: Thanks for the list, very interesting.
Where did you get this information?
If there is one book / table, I can have it?

The bushings, shock absorbers,ball joints, ect. are new on the front axle.The rear axle has new shock absorbers. I know that my wheel alignment is not optimal.Is just "about" set.

This weekend, I check the ratio.Let's see what I have.
I do believe that my car goes into 3rd gear. I will also check.

Maybe I mean only that cries my car at 80 mph. Is my first road cruiser with 425 engine. Therefore, I have no means of comparison.

*****

 

The redline on most 60/70's V8's was higher than that Eric. Closer to 52-5500 rpm.

 

Like I said, I'm being conservative. I wanted to use a speed that you might actually drive at for a while, not one that you'd reach for a few seconds.

- Eric

 

Just to add another experience similar to MDchanic's, when I was about 19 I had a car, non-Oldsmobile, full-size American big block car with 2.73 gears. The speedo went up to 120, and on about two occasions, I thought I would test it. Open stretch, no cops, I took it up. One time, it got to 120, and I brought it back down. The next time, I got up to 120 and kept going until the sweep speedo needle disappeared, somewhere north of 120. Stayed there for a minute or two. I don't remember if it was floaty or not, I was too fascinated by how different 120+ feels than any speed much lower. Brought it back down, parked it, and the next day the transmission had spewed several quarts of fluid. Never drove that car again. In hindsight, I wasn't very bright at 19. I had paid $350 for the car, the tires were whatever I could get for $20 second hand, and the suspension was 20 years old and untouched.

 

The only people who were bright at 19 were Bill Gates and Steve Jobs.

If I had just done like my father said at 19, and taken the tests for PD, Fire and Sanitation...

- Eric

 

I think it was Mark Twain who said at 16 he couldn't believe how dumb his dad was and at 21 how much the Old Man had learned in the last five years.... Tedd