Out of curiosity I have been "collecting" V8 firing orders.  So far I have found 5 unique firing orders for a conventional 90 deg bank angle cruciform crank V8.  For clarity, cylinder numbering is from the front of the engine to the back, so odds are on one bank, evens on the other.
They, along with their twins (cylinders numbered back to front), Ford numbering system equivalent, and a partial list of engines that use them are:

Original        Twin            Ford
12784563    15436872    15486372  Ford Flathead  Lincoln Flathead Ford Y-block Lincoln OHV Buick Nailhead
18547236    14527638    18364527
18736542    12634578    18654273 caddy flathead Olds OHV
18726543    12734568    15426378 MEL wedgeblock Ford FE
18436572    15634278    13726548 Caddy OHV Desoto Firedome Chevy smallblock Pontiac Mopar B AMC 1st & 2nd gen Olds 2nd gen Porsche 928

>>>>>>>>>>>>>>>>>>>>>>>>>>.Needle Valves

The Chevy 4/7 swap simply moves the 90 deg sequence adjacent pairs to another position. The charging robbing effect is identical except for being relocated from 5/7 to 2/4.

Cylinders 5/7 and 2/4 both have the intake ports grouped as pairs with only a divider wall between the ports so it does not alter the geometry of the 90 deg in firing order separated ports.

I have never seen a credible explanation as to how this helps anything other than cam makers profits.

One noticeable thing about the original SBC firing order is that it not only has most names in the list, it also has all the most performance oriented names in its list.

I wonder what firing order Jaguar, BMW, MB, Audi, Ferrari, Rover, Aston Martin, Toyota and Nissan use, that is after they are all converted to the Chev cylinder numbering system. That is by doing the obvious and starting at the big end journal closest to the snout as 1 and counting along in sequence to end at 8 closest to the flywheel.

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