Anyone ever seen this happen? I put together a 62-1 setup for a customer. We spent one day road tuning the Microtech to get the driveability setup. Next day we planned to make some boost pulls to get the tune close then hit the dyno. First pull I made at .9 bar the engine picks up a bad vibration on down rev. Baby it back to the shop. Isolate the vibration to the engine and see a small bit of copper in the oil. Bad bearing we assume. Tear the engine out and on dis-assembly find that the flyhweel key is neatly seperated into two pieces. Has anyone ever heard of this? I've seen keys break in non-rotary applications and it's always appeared that the key was improperly installed half out of the keyway. This one didn't look that way. The keyway is very much intact on both the e-shaft and counter weight and the key itself doesn't apear damaged (other than being in two pieces!) I didn't build this engine and it's surely non-stock. Just wondering if anyone has heard of this? We'll be tearing the engine down to freshen the bearings and turn it tip-top before it goes back in.

 

oo! OOO! we did. you've prolly seen the pics before its on ted website (www.fc3spro.com ->hall of failures -> k2rd motor)



ours sheared because thats what happens when the car is going 90+ mph and the engine stops turning, it also sheared off the stat gear bolts....



i'm thinking with yours maybe the flywheel wasnt tight?

 

Yeah, I've seen those pics. Flywheel nut was the only thing I could come up with as well. My new super duty impact doesn't grunt a whole lot busting these things off but this one came off extra easy. Engine is now down to the nuts and bolts. I may have discovered a new worst porting job in the process.

 

lol. i mention the loose nut thing, cause that seems to be a cause of failure of the miata key.

 

Put some valve grinding compound on the taper, and lap the counterweight onto it. When both pieces show grey all around the touching surface, scrub both off very well. When you build it up the engine, grease up the end of the bearing, so any excess Locktite cannot foul the bearing. Apply one drop of red Locktite

to your finger. Wipe it around the inside of the mating surface on the counter weight. Install the counterweight and key. Warm the counterweight with a propane torch until hot to the touch.

Put one drop of red locktite on your finger. Wipe it on the mating face of the nut. Do not use the locking washer. They are useless.



screw on the nut. torque to 350 - 400 foot pounds.



The key is dead soft and is only there to index the flywheel or counterweight. It cannot withstand any torque at all. Only the tapered fit is transferring torque.



If you get Locktite on a main bearing and it finds a dry spot, it will superglue the crank to the bearing, and on startup, the bearing will shear the tab and spin...........................don't ask.



Lynn E. Hanover

 

 

We did that once on a buddy of mine's Turbo II. Not sure what caused it.



B

 

Not that I'm thinkin' about it again, I think the cause was a chain of events thing caused by a loose front crank bolt. I think the stack began to thrust from being very loose once the front bolt worked its way out, perhaps causing the issue in back w/ the sheared flywheel key. Whaddya think?



B

 

Not thrust, torsional. The engine needs the mass of the front pully system to help null the accellerations of the rotors going over TDC under power. A problem when the flywheel is lightened or removed as in some forms of racing that use dog ring shifted transmissions.



The shock loads are very high. So when just the small aluminum pully is used and high shock transmissions are used, great care must be used when installing the flywheel or counterweight.



I leave out the soft locking washer that comes on the stock engines. It is an invitation for the loss of torque on the big nut. Be sure to grind the pin below flush that keeps the washer from turning.





Lynn E. Hanover

 

thanks lynn. Real helpful info