Today's 160 mph 2.4 Liter Targa is...

[javadog]

Originally Posted by onewhippedpuppy

Jeff, not questioning your assessment, only stating what is possible with a big budget.

I could give you NASA’s budget and you wouldn’t make those kind of numbers with a stock bottom end and relatively stock heads. The early RSRs would turn eight grand and had completely different cylinder heads than the 2.7. Higgins is right...

[island911]

Originally Posted by Gogar

Guy I work with loves telling stories about going 150 in his stock 1981 SC. He seems to enjoy the telling of the stories so I don't ruin it for him. Life's too short....

I'm looking at a factory SC spec. It says 146_mph top speed.

So, give the guy a tail wind of 10mph and a slight down-hill slope, and...

I expect the top speed is at peak HP revs, and the rev limit is just above that.

[javadog]

Top speeds on an SC varied from 135-ish to just north of 140, depending upon the year, body style and options. They typically peaked a couple hundred revs above peak power. To run 150, you'd be turning right around 6500 rpm, which was close to the limiter.

A better than average SC coupe, with spoilers, a lowered ride height and the usual tweaks to the cam timing, injection settings and an early exhaust with sport mufflers could get close to 150 on a good day in winter.

[onewhippedpuppy]

Originally Posted by javadog

I could give you NASA’s budget and you wouldn’t make those kind of numbers with a stock bottom end and relatively stock heads. The early RSRs would turn eight grand and had completely different cylinder heads than the 2.7. Higgins is right...

Not what I was claiming. Only giving an example of what can be done with an air cooled flat six when money is no object.

[island911]

Originally Posted by javadog

Top speeds on an SC varied from 135-ish to just north of 140, depending upon the year, body style and options. ...

Sounds right for a US car.

The 146mph spec I'm looking at is along with a 9.8:1 CR, so that pegs it as a later Euro SC.

[Gogar]

Originally Posted by javadog

Apparently, you’ve never read an owners manual for one of these... Forget the speedometer, you have a tachometer and some charts in the back of the book. If the tachometer is anywhere close to accurate, you can figure the top end speed just as Norbert Singer used to do at Le Mans.

I have, plenty of times, which is why I told the story about my friend's stock 1981 SC that could maybe go 136, brand new. And he enjoyed his story about going 150. That's the premise of me retelling his story. Because the car can't go that fast. Because I read the book.

[javadog]

Originally Posted by island911

Sounds right for a US car.

The 146mph spec I'm looking at is along with a 9.8:1 CR, so that pegs it as a later Euro SC.

That would be the 1981 and later cars. Auto Motor und Sport got one of those to 240 kph, which works out to 149 mph.

[Jeff Higgins]

Originally Posted by onewhippedpuppy

Not what I was claiming. Only giving an example of what can be done with an air cooled flat six when money is no object.

While true, that is completely irrelevant to this discussion. We are talking about a vintage 2.7 with stock cases, stock crank, stock rods, stock (but twin plugged) heads, 10:1 compression JE pistons in stock cylinders, some kind of suitable cams, and PMO throttle bodies with some form of EFI. Yes, with your unlimited budget, we could replace all of that. Then it becomes "Abe Lincoln's axe" - as he described it, "the best one I ever owned. It only needed two new heads and five new handles the whole time I had it".

[kach22i]

I wonder if this is similar to a four valve Wasserboxer or water cooled head like on some flat four VW powered aircraft.

The kit car magazines of the early 1980's were filled with such projects.

[Jeff Higgins]

Originally Posted by kach22i

I wonder if this is similar to a four valve Wasserboxer or water cooled head like on some flat four VW powered aircraft.

The kit car magazines of the early 1980's were filled with such projects.

Porsche finally had to resort to water cooling on the later 935 heads after every single one of them suffered heat related DNF's at either Sebring or Daytona one year. I believe they were still two valve, however.

They did experiment with air cooled four valve heads, as did a number of other (mostly motorcycle) manufacturers. They all learned that it was quite difficult to pull off, due to the inherent "hot spot" between the exhaust valves. Harley uses targeted water cooling, just around the exhaust valves, to address this in their new M8 motor. Williams has apparently found some solution on their Singer motor, running four valve air cooled heads.

The motor under discussion, however, has stock heads. Kind of an interesting question, though, if there would be enough of a market for someone to develop four valve heads for the older air cooled motors. I rather suspect there are other limitations that would preclude extracting the full advantages of such, however.

[dienstuhr]

Last night I was at a cruise night and saw a 240Z. As I’d owned one for 20 years (sold to get my 911) I was somewhat familiar. This car’s 2.4L engine made 150hp new. The teenage owner and his dad asserted that their car now made 250hp with an L28 block and maybe a cam (not sure)... OK. My raised eyebrow suggested my skepticism but no need to pursue further 🙂

[Alan A]

Originally Posted by dienstuhr

Last night I was at a cruise night and saw a 240Z. As I’d owned one for 20 years (sold to get my 911) I was somewhat familiar. This car’s 2.4L engine made 150hp new. The teenage owner and his dad asserted that their car now made 250hp with an L28 block and maybe a cam (not sure)... OK. My raised eyebrow suggested my skepticism but no need to pursue further 🙂

Complete Engine Builds

Depends who built it...

[Superman]

Originally Posted by Jeff Higgins

There is only one way that these old air cooled motors can come anywhere close to these wild horsepower claims - exceedingly high rpm's. ...

This. Torque is power. Horsepower is Torque * RPM divided by 5252. So....a motor making only 250 lb/ft of torque at 10,504 RPMs would be making 500 HP. Island says many things come into play other than the 'air pump' capacity and he's right. Not so much at 3K RPM, but certainly at 8K RPM.