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Anyone have experience with broken studs(there are 8 of them) at the flywheel/crankshaft interface on the AeroVee engine? We have a few broken ones and they are very hard and cannot be drilled very easily. Not sure how they broke and we have heard that VW engines originally had 4 studs. Assumption is that added studs are for increased torque because of generator and magnetron drive power needed. Any help or opinions welcomed.
Thanks

The only way to accuratly get a broken stud out is to bring it to a machine shop and have them edm them out. A cobalt drill may get through the hardened steel dowel but they are a press fit into the crank so there is a really good chance you will either end up with an enlarged or damaged hole trying to drill it out by hand. The 8 dowel modification was originally done for bigger motors than a stock 1600 in the car world. The added dowels were needed to help transfer the torque from the crank to the flywheel to the clutch and transmission. The stock 4 dowel flywheels tended to oval out thr flywheel holes on bigger than stock motors. I dont see a stock aerovee really needing all 8 dowels but probably wouldnt feel right flying with a broken one still in the crank and would suggest contacting the factory to see what they suggest.

Thanks for the feedback-we were thinking only a good machine shop could get them out without damaging the crank. Still kind of wondering how they broke-it was a new crankshaft from Sonex for a rebuild. Thanks again

I had the crank in the shop to have the hub removed due to an apparent typo in the assembly manual related to the front main bearing. (This was a good thing as it was found that the propeller hub hadn't been fully seated on the crank from the factory.)

I had 5 out of 8 dowel pins that had cut-off marks from the factory. All 8 were the same height from the crank. I tried to remove one to check it's length, but as you discovered, this can be very difficult for us mortals. Mine weren't broken, (not in a running engine yet) just shortened for some reason. I had the shop remove them just for good measure and found the 5 to be 1/8 to 3/16 shorter than the other 3 unmolested pins.

The discovery was that the holes in the crank had a corresponding step (probably pilot hole-to-final size) that wouldn't allow the pins to go full depth, and were subsequently shortened for clearance reasons. I acquired a drilling fixture and an 8mm reamer and finished the job of the crank manufacturer.

In the automotive world, the pins aren't as tight as they seem to be in the Aerovee crank, as I've removed them with Vise Grips in the past. I suppose it's possible yours were stressed/fractured when they were installed.

I took my dual-length pins to Oshkosh for show-and-tell, and still have them if anyone is interested.