Porsche 917 flat 12 engine

[Foketry]

To obtain the heads many processing steps are required
the first is to mill at least 2 reference planes, perpendicular to each other , the second was to drill 4 reference holes for the subsequent operations (they are the same for fixing to the cylinders), the combustion chamber and the spark plug hole.

 

[Foketry]

12+1 milled and drilled heads

 

[Foketry]

the third step, contouring of the external profile

 

[Foketry]

fourth step, drilling and reaming valve cage

 

[Foketry]

I just noticed how incredibly thin the valve seat is on the original head. That contact area can’t be but 1 or 2 millimeters! Amazing technology, I wonder what that insert is made of to withstand the heat and not burn out? Unless that’s a 2 step seat, I can’t believe the thin aspect of the outer seating ring surface.

It is true , the valves are very thin and certainly heat resistant, this engine has won the 24 hour race of Le mans several times !

 

[a41capt]

It is true , the valves are very thin and certainly heat resistant, this engine has won the 24 hour race of Le mans several times !

Those engines were a true example of German reliability and toughness. I’m pretty sure the Porsche 917 still holds the top speed record for LeMans (before they added additional chicanes on Mullsanne to slow things up a bit).

 

[Foketry]

Fifth step
Milling of the intake flange

 

[Foketry]

Sixth step
exhaust flange milling

 

[michelko]

Sixth step
exhaust flange milling

View attachment 125543

View attachment 125544

Those chips are flying nice.
Can you say something about the machine and the cutting parameters?
Michael

 

[Foketry]

Those chips are flying nice.
Can you say something about the machine and the cutting parameters?
Michael

Hi Michael
I normally use these parameters on aluminum, 2 flutes end mill 6mm, spindle speed 9000 rpm, cutting feedrate 200 mm / min, stepover 0.5 mm and also some spray of WD40
I applied a double spindle to my Chinese milling machine, 2.2 Kw, 24.000 rpm, air cooled
I use this spindle on aluminum, original spindle for cast iron and steel

 

[Foketry]

I wanted mill the fins on the heads, but I broke the saw blade milling at the first fin, by my mistake , now I have to wait for new saw to arrive.
I did an assembly test, with the 3D printed camshaft box, everything looks correct

original engine

 

[CFLBob]

Hi Michael
I normally use these parameters on aluminum, 2 flutes end mill 6mm, spindle speed 9000 rpm, cutting feedrate 200 mm / min, stepover 0.5 mm and also some spray of WD40
I applied a double spindle to my Chinese milling machine, 2.2 Kw, 24.000 rpm, air cooled
I use this spindle on aluminum, original spindle for cast iron and steel
View attachment 125601

I'm suspecting your Chinese mill is bigger than my Chinese mill but I've thought about doing the same thing with a second spindle. How big is the work area, and how much do you give up by mounting that second spindle? Looks like about 15cm?

Mine is a Grizzly G0704 - which is often known as a BF20L. The spindle won't do over about 2250 RPM so I don't get high feed rates on Aluminum. I use a Fogbuster on mine for cooling, which works well.

 

[Foketry]

I'm suspecting your Chinese mill is bigger than my Chinese mill but I've thought about doing the same thing with a second spindle. How big is the work area, and how much do you give up by mounting that second spindle? Looks like about 15cm?

Mine is a Grizzly G0704 - which is often known as a BF20L. The spindle won't do over about 2250 RPM so I don't get high feed rates on Aluminum. I use a Fogbuster on mine for cooling, which works well.

The distance between one spindle and the other is 150 mm but the working area is reduced by about 50 mm in X, I can move the vice to the right up to 100 mm
my milling machine is similar to Rong Fu RF40, i did it myself 4 axis CNC

 

[CFLBob]

The distance between one spindle and the other is 150 mm but the working area is reduced by about 50 mm in X, I can move the vice to the right up to 100 mm
my milling machine is similar to Rong Fu RF40, i did it myself 4 axis CNC

Interesting development to me - your mill is very close in size to mine, according to the Rong Fu website. That's encouraging.

I built the CNC conversion on mine, full 4 axis like yours, but used some popular plans I bought online.

 

[a41capt]

Loving it! Will the exhaust manifold be cast or built from tubing? I’m really enjoying this build, and now considering what my world would look like with CAD/CAM and CNC.

John W

 

[Foketry]

Loving it! Will the exhaust manifold be cast or built from tubing? I’m really enjoying this build, and now considering what my world would look like with CAD/CAM and CNC.

John W

exhaust manifold will be made of welded pipes as the original engine

 

[a41capt]

I was a pipe fitter and welder in the US Navy, and THAT piece of work looks like it’ll be lots of fun!

 

[Jan Dressler]

I don't know, something at work yesterday reminded me of this thread...

(Though this is from a 908 I guess, not 917)

 

[a41capt]

exhaust manifold will be made of welded pipes as the original engine
View attachment 125609

I was also going to add that it’ll require quite a target deck to make that match up. Interesting how they’ve balanced the exhaust through the expanded first collected system pipe into a common collector to equalize the back pressure.

 

[Willyb]

Really enjoying watching this build. Wonder why they dump the collector for the front three cylinders on the right side into one leg of the three rear cylinders and on the left side the front three collector connects into the secondary collector? Maybe there is something in the way?