I'm back at my MT647 install into my MC-5c, what with sudden warm weather and all. I'm adapting a Cummins ring gear to the torque converter, since I could not source the special MCI flex-plate/ring gear. The TC has 3/8" NF thread bolt holes, the flex plate I do have has 3/8" holes, the Cummins ring gear has exactly 7/16" holes (as in .438") so a zero-clearance fit to a 7/16" bolt. A day's worth of corrosion and the bolts would be frozen in place. So I wondered if Cummins installs have special shouldered bolts, or if I should just use 3/8" bolts. The bolts will not be loaded in shear, friction between the parts will take up all of the starting torque load.
Thanks for your thoughts.
Brian
Here's some stream-of-lunacy way-out-the-box thinking:
There's 0.0625" difference in diameter between 3/8" and 7/16". Why not make a spacer tube from 3 wraps of 10-thou stainless shim stock, or slightly less than 3 full turns if it's too tight to get the bolt through it. I often do this when I'm trying to reduce the gap between bolts and oversize holes - I recently did it when I installed my brand-new Webster KB hydraulic pump on the back of the engine, and the 1/2" bolts were much too loose in the pump's holes. I didn't want any risk of the pump's drive gear and gear coupling being misaligned or off-center, so I used good ol' soda can aluminum that's 5 thou thick and nice and soft to prevent fretting the pump's aluminum ears. If you make a little tube from several wraps of shim stock and insert it in the hole, it will spring out to its maximum ID, sometimes with a little help from a lubricated tapered drift, then the bolt should cleanly go through it. If it catches on the end, just relieve the edge of the first turn of thread.
I learnt this trick when working with bicycles that often have lousy tolerances. I know of several high-dollar bikes with bits of Coca-Cola can between their handlebar and stem - one customer got pissy because the red color was slightly showing, so we just reinstalled it the opposite way!
John
Hey Brian, check out these ARP flywheel bolts. They look like they have a larger shoulder and might be close to what you are looking for.
- Steve
http://www.jegs.com/i/ARP/070/206-2802/10002/-1 (http://www.jegs.com/i/ARP/070/206-2802/10002/-1)
Quote from: stevet903 on May 19, 2017, 03:31:07 PMHey Brian, check out these ARP flywheel bolts. They look like they have a larger shoulder and might be close to what you are looking for. - Steve
http://www.jegs.com/i/ARP/070/206-2802/10002/-1 (http://www.jegs.com/i/ARP/070/206-2802/10002/-1)
It appears that they have a 3/8 x 24 thread, which is standard fine thread (UNF), that's what he needs but I don't think that the shoulder is long enough or large enough. Too bad, that looks close. :(
Thanks for the thoughts! I may use a version of the first idea by buying some 1/32 wall tubing and cutting some sleeves. Those flywheel bolts brought back memories - I used to to stock those when I was building race engines, they got used in a lot of different flywheel applications. They are just a quality 3/8" bolt, no shoulder to speak of. I probably still have some in my bolt bucket...
Brian