Flywheel orientation question

[roscoe]

I'm slowly getting my 5 speed kit in motion and a question arose because I'm going to trim off the lip on the rear edge of the flywheel as part of the lightening process I'm going with.

The flywheel is marked on the lip with a scribed line marking where the flywheel should be aligned with the #4 and # 1 connecting rods when installed on the end of the crank. I'll rescribe the line because it will be removed during lightening. My question is, why would the manual require this alignment unless the crank and flywheel were balanced as a unit when manufactured? Does anyone know if such a sophistocated procedure was done? And last, if I have the machine shop balance the flywheel with the new clutch housing on it, does it make any difference how I install it with regard to alignment with the rods.

When I had a career, I dynamically balanced helicopter rotating parts as routine procedures. I understand about dynamic banance, harmonics etc. and this isn't rocket science but I'm no expert on automotive voodo. When I built the engine up I remember doing the alignment but now I can't really see a reason for maintaining it. In fact, since I am certainly fiddling with the original balance of the flywheel, and installing a diaphram type clutch housing it seems pointless to align it this way any longer. Any thoughts?

 

[Madflyer]

I have not seen anything about this on flywheels a balanced crank for sure. On a high RPM motor maybe say above 10,000 RPM How much is cost for shop as to Alum flywheel. I have always assumed clutch and flywheel was like WAX on WAX off. Nothing about aliment to cyl. Madflyer

 

[red57]

Jon,

I'm stretching my memory but I had a BN1 in about 1970 and I seem to remember that it did not have timing marks on the front pulley and someone at the time told me that the marks on the flywheel were for ignition timing on some earlier Austin application? Whatever the earlier application was, it had a hole in the bellhousing with a removable cover that you could see the timing marks through but the 100 didn't have that hole? Again, stretching memory a lot....

I know my Harley panhead is timed via a hole in the case and a line on the flywheel inside.

My old Massey Ferguson tractor has a Perkins 3 cyl gas engine that is timed by a hole in the bellhousing and a mark on the flywheel - unfortunately, I can't time it other than by "feel" because some PO put the flywheel on in the wrong orientation so the timing mark is in the wrong spot.

If this is the case with the 100, then the marks would be about ignition timing and not about balance. I think it would have been balanced individually and not as a complete assembly - but your machinist would likely know normal practices better than I.

Dave

 

[roscoe]

Dave,
Thanks so much for your recollections, mystery solved. I do believe you are correct that it was for timing and not balance. The only mention of the marks on the fly wheel are in the short section on ifgnition timjng in the BN1/ 2 book.

I think this must have only been for initial setting up of the distributor. Also, there are timing notches on the crank pulley in front and a pointer stamped into the chain cover for timing with a light. The books has an unduly complicated method of static timing for using the flywheel marks for fjnding TDC. A thumb in the spark plug hole and a wrench on the crank pully is my choice. The book even says to pull the valve cover off to se the valves rocking to find TDC. Glad I wasn't a mech at Austin Healey back in the day if you had to go by that.