Crankshaft Dowel Pin 'C' Engine

[Tim Berardelli]

Mark,

Getting back to your original question-find a "high end" machine shop with a Metal Disintegration machine to remove the broken dowel. I've done this in the past when dealing with sheared dowel pins.

[Mark Sabbann]

356-fw.pdf

Here from Spec Book the flywheel angle.
Recommend that you get this little book.

Juha, are you referring to the Maestro's Spec Book? I have that book but don't find that info. I also have the B/C shop manual which doesn't address this spec in the normal flywheel removal/installation pages.

[Ron LaDow]

[...]
Juha, are you referring to the Maestro's Spec Book? I have that book but don't find that info. I also have the B/C shop manual which doesn't address this spec in the normal flywheel removal/installation pages.

Mark,
Probably this one:

img20190905_07585565.jpg (220.77 KiB) Viewed 1348 times

[Mark Sabbann]

So if I am to understand the drawing provided by Juha, there is a 1.5 degree bevel on the face of the area where the soft iron gasket goes, for a shallow dishing of the gasket under the gland nut?
Sorry for the poor lighting in my photo, but as you can see, the seal sits proud of the crankcase, is this normal? As you can see, a lot of black RTV was used too. I found a thread that discusses the seal, trimming it and seating it properly: viewtopic.php?f=1&t=44170. Is it necessary that the seal be flush? I've trimmed the outer lip of my new seal and thought that was enough to avoid the overheating issue.
At the moment without the gland nut in place, there is a gap between the back of the seal and the shim washer. Is that normal? The shop manual indicates that it "must seat flush on the bottom of the oil seal recess".

[Mark Sabbann]

[...]
Juha, are you referring to the Maestro's Spec Book? I have that book but don't find that info. I also have the B/C shop manual which doesn't address this spec in the normal flywheel removal/installation pages.

Mark,
Probably this one:img20190905_07585565.jpg

Thanks Ron, I have the 2nd edition of that book but it doesn't address this measurement, must have been added in the 3rd edition.

[Mark Sabbann]

In my photo you can see the broken pin at about 4 o'clock. The Milwaukee cobalt bits I bought barely make a dent in the dowel pin so I am looking for an EDM shop.

[Mike Smith]

Brad Ripley - Mark, Have you carefully inspected the overall condition of your crank? Determine condition before dealing with the dowel pin problem. Suggest not going any further. Just send the crank off to Walt at Competition Engineering http://www.competitioneng.com/CrankshaftRods.htm for a complete evaluation and possible repair. Also I believe Ollie's can do the same thing, see: http://www.olliesmachine.com/

Mark - this is sound advice - You need people who have successfully carried out this in the past

[Wes Bender]

++2

[Don Gale]

Perhaps the crank was previously repaired and one or more of the new dowel holes was drilled off location, causing all 8 not to share the shear force equally, biasing excess shear force on the broken one? Or the flywheel holes are a bit sloppy, causing the same demise?

[Wes Bender]

I don't think so Don. The crank and flywheel are softer than the dowel pins. The distortion would be apparent. Considering the value of these engines, I think it prudent to have everything checked. It's only money though. How much do you want to gamble?

[Don Gale]

Well, the OP has a few decisions to make. His initial problem was a leaky seal and was sure it would be a quick weekend repair. The unpleasant discovery of the broken dowel certainly complicates things. Now, what are his options?

1. full teardown and send crank & flywheel to the shop for a proper inspection/repair. Does the OP want to take on opening the case and re-assemble himself? Perhaps not at this time.
2. find a machine shop with a plunge EDM and hope they're willing/able to do it in situ on a complete motor.
If not, roll the dice and drive gingerly with 7 new dowels til the next full teardown, probably not the best option considering the risk, no hard shifts knowing it would only take once to screw the pooch, in which case he will be faced with a teardown and extensive machining cost.

It's a crap shoot what I would do. A teardown and proper repair at this point won't be cheap. A teardown later if the dowel bites him in the ass will be even more expensive. If all the other 7 dowels are snug in the crank and flywheel, I'd remove the good ones and replace them with new, cross my fingers and hope the shop can remove the broken one and live with the consequnces, looking for another good crank to have in reserve if needed.

3. what is the motor's current health otherwise? How many more years/miles til it needs a full rebuild?

[Mark Sabbann]

Well, the OP has a few decisions to make. His initial problem was a leaky seal and was sure it would be a quick weekend repair. The unpleasant discovery of the broken dowel certainly complicates things. Now, what are his options?

1. full teardown and send crank & flywheel to the shop for a proper inspection/repair. Does the OP want to take on opening the case and re-assemble himself? Perhaps not at this time.
2. find a machine shop with a plunge EDM and hope they're willing/able to do it in situ on a complete motor.
If not, roll the dice and drive gingerly with 7 new dowels til the next full teardown, probably not the best option considering the risk, no hard shifts knowing it would only take once to screw the pooch, in which case he will be faced with a teardown and extensive machining cost.

It's a crap shoot what I would do. A teardown and proper repair at this point won't be cheap. A teardown later if the dowel bites him in the ass will be even more expensive. If all the other 7 dowels are snug in the crank and flywheel, I'd remove the good ones and replace them with new, cross my fingers and hope the shop can remove the broken one and live with the consequnces, looking for another good crank to have in reserve if needed.

3. what is the motor's current health otherwise? How many more years/miles til it needs a full rebuild?

Don, you have pretty much read my mind with your thoughts.
It WAS intended to be a weekend repair and has grown beyond that.
1. I am not inclined to perform a full tear down so I will look into outside options.
2. I am looking for EDM services but really think I should be looking beyond that to the full tear down and inspection. If I understand the concern behind the recommendation for an inspection, it is that whatever caused the pin to break could have tweaked the crankshaft in some way, beyond just visible elongation of the pinholes.
3. Also in support of a teardown, the car and engine run strong but do have about 230K miles on them. Assuming it is still the original crankshaft, it may be a good time to take a look.

The timing is poor as I have to get the car into storage soon. Depending on what availability I can find in a shop, I may have to reassemble everything as is, drive it to storage and deal with it next Spring. I won't have access while stored.
So, not the best news to get, but maybe the best timed news to get depending on inspection results.

[Martin Benade]

Or tow it to storage and keep the engine. If the engine really has 230k miles i imagine it is ready for a lot of rebuilding. They seldom last that many miles.

[Juha Vane]

The spec book is Porsche P/N WKD420220, available for example here:
https://www.stoddard.com/wkd420220.html

[Vic Skirmants]

Over the years, for various reasons, I have used a crank with 7 dowels; in my RACE engines.
You decide.