Identify Porsche 356 crank

[Al Zim]

Look inside your cleaned canister oil filter. On the center pipe you will see one small hole about the size of a ball point pen. Whatever oil is filtered passes through this hole. Maybe 4% (or less) of the oil at any given moment. The filter was a device to increase sales by stressing engine longevity. It does not work.
Depending on the wear in the case, main bearings and flywheel end play there will be play (read flexing) in the crank. How many times does this occur before the crank breaks..this is unknown. If you are serious about the engine staying original then a new cross drilled crank is in order as well as aftermarket rods. Once the case becomes BAD more than likely it cannot be fixed. Than means BE CAREFUL. We have a large collection of bad stuff here. Because I have (personally) not cleaned up like I should have. zim

[Jon Schmid]

Hello Zim. Thanks for the reply. I now managed to fully disassemble the crank and measure it. To my surprise it seems to be completely at production tolerances. Amazing! Pls see image.

Not at all "amazing." Properly maintained 356s in normal use rarely show crankshaft journal wear at teardown. That is the reason that the current hype pushing adding full flow oil filtering to the 356 engine is silly.

Hi Harlan, when the 1600 Super engine on my 1960 Roadster finally had a full rebuild about 15 years ago, the original crank only had to be turned down to one undersize from stock. This was after 45+ years of constant use but also constant maintenance. Stock bypass oil filtration system FWIW. Take it for what you will...

[Jon Bunin]

Sometime late in 1961 the Super engines received a crank that was CROSS DRILLED in the rod bearings. These engines numbers were preceded with an engine number that started with ZERO (0) I would assume that there were a great deal of cranks laying around the shop and these were used on the Normal engines. S-90 cranks had a 55MM #1 Main Bearing they were probably hardened which precluded and additional modifications. Zim

Hello Zim. Thanks for the reply... I have indicated the cross drillings with green. Did all 356 cranks not have these cross drillings? Any idea from what year the crank is from? ...

The 'improved oil bore system" was introduced with the counterweighted Super 90 crankshaft, effective June 1962.
It was then introduced in all crankshafts, and in replacement crankshafts for earlier models.
The effective dates and engine numbers for all versions are indicated in these Service Bulletins.

The easiest way to identify the improved system is the presence of soft-plugged drillings outside the bearing journals (arrow on C crankshaft, below).

[Dick Weiss]

Tom,

The crank you show is the earlier version w/only 1-oil hole feeding the rods from the small oil pump.
The later cross-drilled cranks have oil feeding the rods from the larger oil pump which are used
in all later (Sept. '60?) 356 B/C/912 engines.

Dick

[Martin Benade]

Would a cross drilled crank be an upgrade on a small pump engine, or a mismatch?

[Jon Bunin]

The crank you show is the earlier version w/only 1-oil hole feeding the rods from the small oil pump.
The later cross-drilled cranks have oil feeding the rods from the larger oil pump which are used
in all later (Sept. '60?) 356 B/C/912 engines.

Dick, please read the factory service bulletins and examine the factory illustration I posted.

The "1-oil hole feeding the rods" crankshafts were used through mid-62, and with the larger oil pumps too.
If you think otherwise, please provide some evidence or proof to support what you're posting.

[Tom Markussen]

Jon Bunin: Amazing documentation you have. Thanks a lot. German precision engineering. A pleasure to read.

I still haven't been able to find information related to the two numbers on the crank. To me it looks like originally stamped numbers from Alfing. BTW, the company Alfing is still fully active, with production close to Stuttgart.

I feel optimistic about my engine project "P 70743".The crank measures to factory spec, so does the rods. The cam is a 912 cam. The cylinders(steel)/pistons(alu) are 1720 ccm (probably the Japanese ones). Heads needs to be measured now.

[Jacques Lefriant]

Hi
Didn't Scat revert to the earlier oil drillings and called it straight shot?

[Dick Weiss]

So it goes Jon; I didn't pull out my Tech Bulletins to verify, I just made the request quickly.

[Al Zim]

In 1962 Cross drilled cranks were factory installed as a running modification. The Case serial number started with a 0 (Zero) I guess by 1963 models all the cranks were crossed drilled (that makes your 1963 crank 60 years old) It is best to use rods where the caps and the beam are both numbered. This indicated that the later style rod bearings were necessary. The break usually occurs where the beam of the rod attaches to the area of the rod bearings. That is why the indent on the rods moved to the other side.