So I have a longgg private driveway..... 128mph @ 7800ft. in OE 74 base model?

[manbridge 74]

Sort of caught me by surprise. Anyone think the PO changed a few items?

[Bob Kontak]

Aside from speedo error, if the car is running well, it's probably realistic for a stock 74.

Midyear 911's are in the 90+ mph range for the 1/4 mile. Assuming 10% speedo error, that gives you another mile to increase 25 mph to 115. If the mileage you state is genuine, then you got a rocket, me thinks.

Had my 81 at 135 on the Ohio turnpike going east between 77 and Rt 8 - slight downhill. Was bragging up a storm until I used a GPS next go-around. 123mph - same stretch of road.

Would be interesting to know how much road is needed to get these cars to genuine top speed. Our cars would be in the 130-140 range, I believe, but something has to give - meaning time - to get that last 20mph out of them

[Evan Fullerton]

My '75 at the time put down 167whp and would do an indicated 150mph + (~where 165 would be if the speedo digits went there) on taller then stock tires.

The skinny fenders make them slippery.

[RWebb]

you realize BoxsterS can go 160 mph, right?

[Jerome74911S]

Originally Posted by RWebb

you realize BoxsterS can go 160 mph, right?

Maybe, but then they don't have skinny fenders, or skinny motors, or skinny drivers.

[don gilbert]

Evan, you need to put the GPS on the 75. Only way it can get to 150 on its own with a stock 2.7 is off a cliff. Sorry, its just true.

[dafischer]

That sounds like a fine driveway, not just long!

[CountD]

Originally Posted by don gilbert

evan, you need to put the gps on the 75. Only way it can get to 150 on its own with a stock 2.7 is off a cliff. Sorry, its just true.

Classic.

[Evan Fullerton]

Evan, you need to put the GPS on the 75. Only way it can get to 150 on its own with a stock 2.7 is off a cliff. Sorry, its just true.

Believe what you will but an honest 150mph is only a little over 6000rpm in 5th on an 8-31 R&P car. 7000RPM in 4th is 140mph.
http://www.californiamotorsports.net/75-79%20915%205%20speed%20stock%20gears.pdf

[don gilbert]

According to your graph, why dont you just throw some s cams in, then you can go 170. Nice if it was true. Might do 120-125 on a good day, with a tail wind, on a slight down hill grade. I know, had one. Think about it, 165 hp, 150 mph? Takes a little more than that. Study up on E=mc squared.

[IROC]

Originally Posted by Evan Fullerton

Believe what you will but an honest 150mph is only a little over 6000rpm in 5th on an 8-31 R&P car. 7000RPM in 4th is 140mph.

Top speed is not gearing limited in this case - it's drag limited. A stock 2.7 will not reach 150 mph (not enough hp to overcome the rolling friction/aerodynamic drag). I'd guess closer to 135-140 mph on a good day. I did some calculations years ago and it seems that (from memory) you would need 230 hp or so to reach 150 mph.

[dipso]

Speedometer is stock, does that count?

[prebordao]

I think that for a stock S in 74 the factory quoted 140mph.
Can anyone attest to that ?

[dipso]

I showed 135 in my stock 2.7. It was slightly downhill and red lined.

I think that for a stock S in 74 the factory quoted 140mph.

Can anyone attest to that ?

[jager911]

I maxed out at 144mph, 6000rpm in 5th, stock 915, but with slightly tweaked 3.2L, verified with GPS and 915 gear chart. My front end gets light at that speed and I need to add a splitter.
Tire size also affects effective gearing/speed.

[Ronnie's.930]

Originally Posted by Evan Fullerton

My '75 at the time put down 167whp and would do an indicated 150mph + (~where 165 would be if the speedo digits went there) on taller then stock tires.

The skinny fenders make them slippery.

Gimme some of what you're smoking!

[McLovin]

Only if it's a Targa.

[Bob Kontak]

Originally Posted by Evan Fullerton

My '75 at the time put down 167whp and would do an indicated 150mph +

Evan,

Even though you are getting some push back, realize things could be worse. :-)

Hint: "It puts the lotion in the basket"

[Evan Fullerton]

No need to smoke anything. Porsche rated the 1973 RS at 152mph. If we use 15% drive line loss, a '73 RS makes 178.5whp. My car with a fairly stock 3.0L made 167whp. Smaller rear fenders, smaller side view mirrors, below euro ride height etc. (my car is not very original in any respect) make up the difference. 150ish mph is an entirely believable speed out of a very nearly stock early 911 so back to the OP's original question. 128mph at altitude is a believable number.

[Reiver]

learn to read your tac....put your gearing, rear end, tire size in and get speeds....I never use my speedo as it is off by about 6mph, but that varies at certain speeds....common in P cars for some reason.

Gear Ratio Speed Calculator