Originally Posted by CR94
Originally Posted by Number_35
Originally Posted by Chris142
Don't all inline 6 use the same 153624?...
I have an ancient Motor Auto Repair Manual - 1977-83 Models. The specs for the Ford, Chevy, and Mopar inline 6-cylinder engines all list the firing order as 1-5-3-6-2-4.... I would guess that the 300 is the same as the Ford 200 and 250 listed. ...
The 200 and closely related 250³ were a different design than the 300 (and 240). It may not matter, if Chris is correct about all I6's. My owner's manual for a 1962 Chevrolet shows the same order, and that was a different design (specifically, the last of the ancient "Stove Bolt" Sixes) than 1970s Chevrolet engines.
It's pretty much determined by the architecture of the inline 6 - the cranks are always such that 1 & 6 are at TDC at the same time, so when one is at the top of the compression stroke, the other is at the top of the exhaust stroke. 120 degrees later, 2 & 5 come up to TDC together, again one at the top of its compression stroke, and the other at the top of its exhaust stroke. And 120 degrees after that, 3 & 4 come up to TDC together.
By definition, Cylinder 1 is fired first, so we know that Cylinder 6 will come back to TDC 360 degrees later to be fired, so we know that the firing order will be 1 - x - x - 6 - x - x.
The 2nd cylinder to fire will be #5 or #2. Engine designers generally try to not have adjacent cylinders fire consecutively, and #1 has just fired, so In this case, it will be #5 that fires 2nd, instead of #2 (which we know will be back to TDC, this time at the top of its compression stroke, 360 degrees later). Anyway, we now have 1 - 5 - x - 6 - 2 - x.
The 3rd cylinder to fire will be #3 or #4. As before, #5 has just fired, and we want some separation, so we won't fire #4 - it will be at the top of its exhaust stroke. Therefore, #3 will fire third. 1 - 5 - 3 - 6 - 2 - 4.
I think the only way there could be a different firing order would be if for some reason a different crank configuration were used (e.g. with 1 & 6 followed by 3 & 4 followed by 2 & 5) - but I've never heard of such a beast. Just checked the 'net for the firing order on a Datsun inline-6, the only non-domestic straight six I could think of offhand - it's also 1 - 5 - 3 - 6 - 2 - 4.