How much HP will a 915 stand?
Mine is fresh, but still.. Will it survive 300hp if you treat it right?
I want to drop my 2.4 out for a restore, but I am not willing to be without my car.
What makes a good 300hp engine that will bolt in? 3.4? 3.6? ETC?
Planning to build an RS, or Ruf style car to play with that this engine will go in...
72 911S Targa #0807 95+% German.
Paul Harrop 12.5% German.
Early S #2059
A healthy 915 will handle just about any amount of street horsepower you can give it. Even in lots of shorter racing applications they do fine without coolers, oil spray bars etc. They ate evolved from the racing tranny used in the 908s
I ran a 915 with a 3.0 Liter Turbo engine for years. Without issue. I would say any more than 300 Hp... Would be questionable. T
1965 911 Factory Paint to Sample Orange
1967 911S Bahama Yellow
1968 911 S Blood Orange
1971 911S Gold Metallic Peter Gregg
1974 Carrera RS Blue Metallic
1990 RUF RCT Estonia's car
It's not so much the HP, it's the torque you make it suffer through. You can have 500hp at 12k RPM and there is hardly any strain on the gearbox.Originally Posted by dummkopf
~J~
air cooled only
I built a 3.8 RS spec engine 325hp & 299tq and put it behind a nothing special ALU 915 in a 73.
Is it even worth thinking about using a magnesium 7:31 915 with a 3.6
Light Yellow -74
@lagteknik
With the steel bulkhead in the Mag case and a reinforced side cover, I think you’d be ok.
One of the problems in running earlier transmissions in applications with increased engine displacements and torque is their smaller gears with less load-bearing surface, and smaller bearings with fewer rolling elements.
The earlier transmissions will run at higher temps, and those smaller gear surfaces and bearings will break down sooner. There will also be a higher degree of power loss.
They can also limit your clutch and axle options, and some had design issues which were problems even in their normal applications.
Of course, it also depends on how hard and how often the car is run. If it's mainly a weekend car for club gatherings and tours, it will probably not overload an earlier, smaller transmission too much.
Jon B.
Vista, CA
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