How does a V-12 Work?

[abelincoln]

After more than a year of re-assembly, I'm now looking at how the 48 V-12 fires. The engine is 75 degrees between banks, and the crankshaft throws connect rods common from both sides. In the owner's manual, firing order is 1-4-9-8-5-2-11-10-3-6-7-12. The dual point distributor has points that look to be 90 degrees apart. So the right, even numbered bank would be delayed by 45 crankshaft degrees. The distributor has a cam that connects two coils each with three cylinders, a timing break due to unequal spacing for the next three. Thus each side of the distributor fires three plugs on one side, then three on the other side.

I've been told firing angles are 0-45-120-165-240-285-360-405-480-525-600-645 degrees. So cylinder one fires at 0, no. 4 at 45 deg, no. 9 at 75 deg later, etc. So it seems to me that cylinder no 2 should fire at some multiple of 75 degrees, but seems to be 15 degrees early. What am I missing? Those Leyland engineers who came when Ford purchased Lincoln were pretty cleaver in 1935.

Thanks

Abe

[peecher]

Abe, the Lincoln V12 fires un-evenly due to the common rod journals and 75 deg "V". Each bank of 6 cylinders fire evenly but side to side is off set. The points in the distributor do not "break" at 90 deg's apart, they too are offset. I guess the amazing thing is how smooth they run.

[abelincoln]

OK, I think I figured it out. If you plot the firing angles as vectors, you will see that there is a 75 degree spread between 1 and 2, 3 and 4, etc. Wonder how long it took the Lincoln engine folks to come up with this. pretty ingenious I think.

Lincoln firing angles0001.pdf

[Guest prs519]

That is interesting, Abe! How are the cylinders numbered....bank to bank, or even odd, or ??

[peecher]

Left bank front to back, odd numbers; right bank front to back, even numbers.