What Are the Chances?

[dibbons]

I pushed my '72 Satellite outside into the light to perform a little maintenance, mainly to lubricate the hood hinges. Vehicle was last started last week.

After finishing up with the driver's side hinge, for some unknown reason I decided to take a peek at the timing marks. Much to my surprise, they had lined up EXACTLY at TDC all on their own the last time the motor came to a stop!

 

[Ben Drinkin]

1 in 360? Just a guess.. I'm not real good at math..

 

[dibbons]

I agree in simple terms that, at first glance, the chances are about 1 in 360.

However, the other factor to consider is how often do I check the position of the timing marks after shutting the engine down--basically never. So now, what are the chances the first time I decide to examine the position of the timing marks after all the engine cycles beforehand that the marks are aligned.

Kinda of like looking out your window for the first time and seeing a solar eclipse? Or maybe inserting one coin in a one-armed bandit and hitting the jackpot.

Here is some homework for our brothers here, everyone make sure to check your timing marks the next time you find yourself in the garage and report your findings.

 

[spl440]

Actually probably less than 1 in 360 on shut down. all depends on compression, and timing of exhaust and intake overlap.

 

[Max1196]

A V8 will have a tendency to always stop in one of four positions. Usually just before TDC of the 8 choices (which translates into 4 harmonic balancer positions). This is due to the cylinder coming up on compression, creating the resistance. Take a look at a well wore out ring gear on a flywheel, on a V8 there will be 4 positions that are more wore out than the remaining teeth, I6 will have 3 bad spots accordingly. So stopping at or near the TDC is more like a 1 in 4 chance with your V8!

 

[dibbons]

Good point. To postulate this a little further, I should determine if cylinder one is/is not on the compression stroke.

 

[dibbons]

Another 1 in 1000 feat accomplished at the supermarket this week?

Purchased some bananas (bunch of 4), baby carrots (pre-packs of 12 oz each), 10 avocados, and loose Mexican squash I figured was enough for two dinner meals. At home, I reviewed my receipt to find I had bagged exactly 1.000 kilos of the squash.