Flywheel bolt interference

[SmokeyC3]

In defense of the OP. I have a spare 8 bolt flywheel out in the garage. I had to go take a look. 1 hole measures exactly 7/16" the other seven are .012" bigger. Interestingly on the 4 bolt flywheel I have all 4 are 7/16" the same as the small hole on the  8 bolt. Unfortunately I can't seem to find any flywheel bolts to help further.

[Dodgeb4ya]

Enlarge the one hole a few thousanths..... be done with it.

Or have a machine shop make up a one only special bolt.

[Jeff Balazs]

Interesting little mystery. I have run into a few things like this over the years.......and there is usually a reasonable explanation at the end.

My guess is that it has something to do with the initial assembly process.....perhaps an indexing fixture or some step used to speed up assembly at the plant.

 

I had a fascinating experience years ago when I was working on an antique British bike that belonged to a friend of mine. He had found a competition bike made by the factory back in the early 50's. When he got it ...it had been sitting for many years and would not turn over. When we tore it down we found some special witness marks and studs that were not part of the assembly on a standard road engine. This was in the days before the internet and I had to call over to England to get parts for this rare bird. In taking with the parts man I found out that we could determine exactly who had assembled this engine just by the way the witness marks were made. It turned out that we had an engine that had been assembled by one of the greatest trials riders of all time. Gordon Jackson won many championships and still holds the unbelievable distinction of being the only man to ever finish the Scottish Six days Trial with a one point deduction. Turns out that in those days when you rode for the factory you also worked in the factory. Because there were never more than 4 or 5 workers assembling engines in the competition dept. and they were all specialists it was pretty easy to figure out who built what.

 

Jeff

[my48stake]

In defense of the OP. I have a spare 8 bolt flywheel out in the garage. I had to go take a look. 1 hole measures exactly 7/16" the other seven are .012" bigger. Interestingly on the 4 bolt flywheel I have all 4 are 7/16" the same as the small hole on the  8 bolt. Unfortunately I can't seem to find any flywheel bolts to help further.

Sounds just like what I'm seeing.  I'll remeasure everything and see if I'm missing something.

[SmokeyC3]

I'd measure the od on the bolts and compare it to the one hole. The one hole must be a press fit to aid in assembly and alignment. As I stated earlier, on the older four bolt flywheel, all four holes are the smaller size. I've had the six bolt flywheel out of my truck, also had a spare six bolt flywheel which is now bolted up to a 1953 241 ci engine. If my memory is correct...  all six bolts on those were press fit. Hope that helps.

[my48stake]

I'd measure the od on the bolts and compare it to the one hole. The one hole must be a press fit to aid in assembly and alignment. As I stated earlier, on the older four bolt flywheel, all four holes are the smaller size. I've had the six bolt flywheel out of my truck, also had a spare six bolt flywheel which is now bolted up to a 1953 241 ci engine. If my memory is correct...  all six bolts on those were press fit. Hope that helps.

Mild persuasion with a rubber mallet proved to be the key to getting the bolt in.  Thanks for all the help!

[Dodgeb4ya]

Couldn't have been too tight a fit to force in with a rubber mallet

[Don Coatney]

Suspect there may be some burnt oil that has turned into shellac in that hole. Try cleaning it with a sharp small bladed knife.

I suspect the rubber mallet was enough to break through the shellac.