remember the firing order 15 to young- 36 to old- 24 just right.

 

It all depends on your point of reference.

 

If you think about the 153624 firing order, and the fact that it's a 4-stroke (two revolutions per spark), you'll see that an inline six is essentially two triples connected end-to-end (and not three twins connected end-to-end). This has ramifications when designing headers, or dual carb intake manifolds.

The question above, about Ford and GM calling different cylinders "number 1," is pertinent to Ford and GM V-8s, not inline sixes. Understandable confusion.

 

Just in case you are used to a V8, the I6 counts clockwise on the distributor cap.