[gtobird]

This flywheel came on my 68 Bird and as far as I know is original to the car. Note that it has 3 balancing holes on the backside as shown. No other balancing holes were drilled anywhere. I put it on a cheapo bubble tire balancer and when I added an ounce of weight near the outer edge (by the white dots) it did balance out which lead me to believe this is probably original as I believe it is supposed to be 6 inch ounces out of balance. Note that the two holes close to each other are about 3/4 inch deep and the one on the opposite side is only about 1/2" deep.

I thought there were only 2 holes drilled to balance these, but I can certainly see that the factory could have added a third hole on the opposite side if the first two removed too much material. What do you think?

Old Joe

[gtobird]

Update: I did some online searching on this topic and there were two points made that make me believe these 3 balancing holes were factory made.

1.) GM did indeed intend to use 2 holes to balance Pontiac flywheels, however many of them in 1968 actually received 3 holes to get them to balance properly.

2.) The factory made holes were typically 3/4" and 1/2" deep, the same as on this flywheel.

I also used a caliper to check what the actual distance of these holes was from the edge of the outer ring on my flywheel. They are virtually identical. I have a hard time believing a machine shop could have matched it that close to the distance of the other 2 holes, nor would they likely have even tried to. The diameter of the holes is also an exact match. So far I've heard nothing to the contrary so I'm calling this a factory balanced flywheel.

Originally Posted by gtobird

This flywheel came on my 68 Bird and as far as I know is original to the car. Note that it has 3 balancing holes on the backside as shown. No other balancing holes were drilled anywhere. I put it on a cheapo bubble tire balancer and when I added an ounce of weight near the outer edge (by the white dots) it did balance out which lead me to believe this is probably original as I believe it is supposed to be 6 inch ounces out of balance. Note that the two holes close to each other are about 3/4 inch deep and the one on the opposite side is only about 1/2" deep.

I thought there were only 2 holes drilled to balance these, but I can certainly see that the factory could have added a third hole on the opposite side if the first two removed too much material. What do you think?

Old Joe