Evolution of the 4 Cam (Fuhrmann) Motor

[daepp]

[daepp]

Grady: - you're right as usual. Here's a couple of mine:

[Flieger]

What is the recommended redline on these motors? Was it different for early motors compared to the 587/3? I understand that racers would often overrev them back in the day since it was faster and they would survive a while like that.

[daepp]

[tazzieman]

Originally Posted by DAEpperson

Evil lurks behind! Outstanding, where dya find that?

[daepp]

It was posted in the Engine Porn thread. I was hoping someone would know something about it.

[Por_sha911]

Originally Posted by chris_seven

Any camshaft will suffer from torsional vibrations and they are parametric in nature and self-induced. These vibrations will cause dynamic phase errors in the valve timing and it is unlikely that a distributor advance curve could compensate.

To resolve the phase changes involves some quite tricky non-linear differential equations even at constant speed and when you add in angular acceleration it is even more difficult.

The biggest problem of all would be if the cam were to be excited so it reached its natural frequency as it would then go completely out of control and perhaps even snap.

Obviously the less the number of lobes on the cam the greater the ratio of peak to mean torque and the more the phase variation. and hence the likely reason for the use of flywheels.

Does a four cam, four cylinder engine with two valves per cylinder only have two lobes per cam?

The variation in torsional load will affect the complete driveline of the cam. The bevel gears themselevs will be relatively stiff compared to the shafts and can probably be neglected.

The type of follower used will also have a signifcant effect as the coulomb damping associated with flat tappets will tend to damp any harmonics.

All that sounds like:

[tazzieman]

The 4 cam 's success was directly related to the enhancement whereby

it may be employed in conjunction with a drawn reciprocating dingle arm to reduce sinusoidal depleneration

[intakexhaust]

Originally Posted by tazzieman

Evil lurks behind! Outstanding, where dya find that?

Bigger question is, why in there?

[tazzieman]

Originally Posted by intakexhaust

Bigger question is, why in there?

Maybe has one of these?
Brand New Porsche 4-Cam Engine Anyone? | The Chicane

[daepp]

Originally Posted by intakexhaust

Bigger question is, why in there?

Agreed - think of that high-reving engine hooked to the gear reductions on each wheel?

[sea911]

Here is one some of you that live in the NW might have seen before.... Rumor is he traded it for a pushrod motor in the 70's.

[daepp]

Originally Posted by sea911

Here is one some of you that live in the NW might have seen before.... Rumor is he traded it for a pushrod motor in the 70's.

Wonder where they put the dry sump?

[sea911]

It's under the back window all polished up. Wish I had a picture here at work. That bug also has the gauges and brakes from a 356.

[kidrock]

Originally Posted by DAEpperson

Agreed - think of that high-reving engine hooked to the gear reductions on each wheel?

I'm sure they pulled the old reduction box trans and replaced it with a re-geared ("freeway flier") trans with half-axles and CV joints.

[dkirk]

It looks like this beautiful engine will be back in limited production again - not from Porsche but from Capricorn Automotive GmbH of Germany. The expensive Hirth multi-piece crankshaft with roller bearing crankpins has been replaced with a single piece forged crank with conventional pressure lubricated journal bearings. Otherwise, the engine is a virtual duplicate of the original. Here is a link to their site:

http://www.capricorngroup.net/fileadmin/files/images/capricorn_Anzeige_Motorsport_UK.pdf

[daepp]

Old thread I know, but if you've ever lusted after a Fuhrman 4 cam, now's your chance.
(And, FWIW, the comments on this one are extraordinary. Sure wish Grady was still around - sigh...)

https://bringatrailer.com/listing/porsche-fuhrmann-four-cam-engine/

[Racerbvd]

Have you guys seen this yet?

[Steve F]

Wow!!

[GG Allin]

That's Perfect Power building that motor.