Hirth Roller Bearing Cranks

[Carrera_The_Kid]

As some of you know I did a three piece article on Hirth cranks some time back. I focused on the history behind the Hirth family, the crank and the various design variations.

Master 4-cam mechanic Bill Doyle just did a three piece article focusing on the assembly of Hirth cranks for the 356 club magazine. I urge all of you out there to go and read these articles, they are fantastic! Hal's pictures really brings to life how complicated these cranks are and what is involved in rebuilding them. Highly recommended

[Meissen540]

Joris,
You did a great job on your articles. Thanks for taking the time to create them.
Your and Bill's articles compliment each other nicely.
Anyone who hasn't read these should. Bill's write ups are in the 356 Club magazine.
Thx
Tom

[MMW]

I assume these are in the Registry mag? Is there a way to read them if your not a member?

[JTR70]

Hey Joris,
Just to be clear the mains were not roller bearing correct; only the rods?
Justin

[Carrera_The_Kid]

HI Justin,

The early push rod roller cranks only had roller rod big ends. The 4-cam ones had roller big ends and roller mains.

There are some cranks with anomalies both 4-cam and pushrod but these are special cranks which were never produced in larger numbers

[JTR70]

Thanks Joris, very interesting. As I understand it these roller cranks were not long for the street due to lugging of the motor by the avarage driver/owner. What would fail due to this driving style? Would the rollors gall and seize? Which would fail more commonly, the rods or the mains? Justin

[Steve Heinrichs]

Gang,

I agree that Joris' recent articles are excellent!!

In addition, in the book that is looking more and more like late September although it is being worked on seven days a week now, the upcoming book will have about 100 pages of the full 4-cam story and many photographs. Written by my co-author Rolf Sprenger, who was at Porsche for 30 years, it is quite comprehensive. Also, as many of you know, the book will list each individual 4-cam motor and where is went (some were spares and we are missing a few). And, the chassis list for 4-cam cars will show every car and which motor it received.

Steve Heinrichs

[JTR70]

Steve, the book sounds like its going to be bursting with all sorts of historical data. I know you have to draw the line somewhere and this may not be included but were there P.O. documents on the number of race parts produced? Like how many GT tanks were ordered, how many 60MM drums ordered and the like. I know these parts are rare but was curious as to how rare. Thanks and looking forward to the book! Justin

[Steve Heinrichs]

Justin,

Unfortunately, no. No such records now. Likely never were. Even the number of blank 4-cam cases left over/later sold/ordered is not known.

We do not show any info re blank cases or other 4-cam parts, except to note, where we have noticed it, 356 4-cams with big tanks.

Steve Heinrichs

[Carrera_The_Kid]

Steve,

Very much looking forward to the book.

Writing my pieces for the registry I learn new things every day and realize how little I actually know about these fantastic engines!