"Hirth engine"?

[Formerly Steve Wilkinson]

I've been criticized by a reader of my book "The Gold-Plated Porsche" for referring to "the Hirth engine" in a Carrera Speedster I once owned. He says there's no such thing and points out--correctly, of course--that it was designed by Fuhrmann and therefore should be called "the Fuhrmann engine" if you're referring to a four-cam 356/356A.

I'm sure he's right, strictly speaking, but I do seem to remember to casually referred to it as "the Hirth engine." Of course today Hirth makes everything from snowmobile engines to very light aircraft powerplants, so that term would today, certainly, be inaccurate.

But am I misremembering? Was "the Hirth engine" never a common term for Carrera engines?

[djpateman]

Wasn't the Hirth engine the one with the roller bearing crank that was made in multiple pieces so the bearings could be installed? So it was really a "Hirth" crankshaft. It was used in many but not all Carrera engines. The 4 cam engine was commonly referred to as the Fuhrmann engine.

[Formerly Steve Wilkinson]

Yes, that's exactly the engine I'm referring to, and I understand that the crank was Hirth, the designer was Fuhrmann. I owned one. My question is, was it ever colloquially referred to as "the Hirth engine"?

[MarKoBrow]

I was under the inpression it was called the Type 547 engine Also called the Fuhrmann 4 Cam, named after Ernst Fuhrmann and future chairman of Porsche. Hirst was the manufacture of the roller bearing crankshaft that was used in the 547, A version of the Hirth crankshaft was also used in some racing 356 engines.
I actually never heard anyone refer to it as a Hirth engine

[MarKoBrow]

Steve I have been meaning to tell you for sometime how much I enjoyed reading your book, it not only reminded me of my misguided adventures with my Cobra and Porsche but it gave me hours of fun reading about yours

[djpateman]

Originally Posted by Formerly Steve Wilkinson

My question is, was it ever colloquially referred to as "the Hirth engine"?

The simple answer, AFAIK, is no.
Fuhrmann 4 Cam, absolutely.

[Gunzel]

I have had Carrera Engines since the late sixties, and still have them, I have also had 356 roller crank engines, and still have one. The 4-cam engines were basically never called a Hirst engine, and except in books were never called a Fuhrmann engine. They were called a 4-cam, or a Carrera engine.

[erik modin]

The engine is the 547, aka Carrera four cam, designed in 1952-53 by Fuhrmann for the 550 Spyder. It is not a Hirt engine and was never referred to as such by Porsche. The Carrera engine is an all Porsche design with a Hirth crankshaft. Hirth Motoren GmbH was formed in 1927 in a brake up from what became the Mahle company. (Mahle made pistons and cylinders for Porsche.) Hirth aircraft engines was successful with the HM 60 four cylinder engine in the Klemm aircraft, used as a trainer during the thirties by Luftwaffe and a few other air forces in Europe. After the war aviation was banned in Germany and Hirth turned to building smaller industrial and snowmobile engines. The Carrera crank was basically a copy of the design from the 1930 four cylinder aircraft engine, with dramatically shortened stroke. The reason Porsche wanted the rollerbearing Hirth crank was its very low friction. The fourcam engines would in racing rotate at 8-9000 RPM and at that high engine speed the friction of a plain bearing crank could result in a power loss of 5 to 10 % and the oil reaching critical temperature. The Carrera engines were very successful in racing, but poor maintenance destroyed the sensitive rollerbearings. Porsche did not have the tools to rebuild these cranks themselves and sent them back to Hirth. According to rumor the Hirt people got tired of crazy Porsche race drivers hounding them and by 1959 they stopped making the crank. The truth is probably that they didn't make enough money on the small numbers of cranks needed for the carrera production. The 356B and C model Carreras had all plain bearing cranks of Porsches own design and needed separate oil coolers to keep the oil temp at bay.

[Mr9146]

Originally Posted by Gunzel

They were called a 4-cam, or a Carrera engine.

Yup.

[356RS]

Great information and history Erik. Thanks

[912UK]

From my limited understanding Hurth = Cranks with roller bearings

[Matt Monson]

When I was working for Tom Conway, we never referred to the engine's as Hirth. We did talk often about the Hirth roller cranks, but never called the whole engine that. It was just a 4 cam engine.

However, I personally don't like focusing on such minutae. If I were reading your book and saw a reference to the Hirth engine I would know what you meant and wouldn't give it a second thought. Some people worry about names too much, IMO.

[912UK]

What Matt says

[Flieger]

So is a Hurst Olds actually a Hurst?

[aadrew10]

Is it Hurst, Hirth, Hurth, Hirst, or Hirt?

[Matt Monson]

Originally Posted by aadrew10

Is it Hurst, Hirth, Hurth, Hirst, or Hirt?

To my understandng, Hirth makes the cranks. Hurth makes the gears. I don't know about the rest...

[Formerly Steve Wilkinson]

Hurst makes shifters (not gears); Hurth makes marine gears; Hirth today makes two-cycle engines and back in the 356 days made its roller-bearing crankshaft, Hirt (Al) plays the Dixieland trumpet, and Hirst (Damien) makes art. Don't know about Hurt...

[Matt Monson]

Hurth also made the gears in your 911sc's 915 gearbox.

[MarKoBrow]

Hey Matt, I think the gear manufacture is Hirth Gears and the manufacture of the Crankshaft was also called Hirth. I did a search a little while ago and found numerous companies in Germany with the name Hirth including company a company that makes recreational gearboxes (?) and a variety of machine related items and then there is Hurth which is associated with ZF hence the Porsche 915 reference.

Off topic here, what is your opinion of the torsen type diff in a 901 transmission? I am almost done my engine and need to pay a little attention to the transmission. Second thing are you moved n yet and open for business?

[Matt Monson]