GM firing order change over the years.

TransAmDan

Forum Admin
Staff member
Came across this interesting article about firing orders.

https://www.lsenginediy.com/gm-gen-iii-ls-pcmecm-change-firing-order/

It seems to indicate you can just swap the firing order. Surely this is the decision of the crank and cam? Unless the teo cylinders you are swapping are at the same point in the cycle surely you can't change the firing order.

116.jpg
The firing order for the Gen I small-block engine is 1-8- 4-3-6-5-7-2. The firing order for the LSseries engines is 1-8-7-2-6-5-4-3. Notice that cylinders 4 and 7 have swapped, and cylinders 3 and 2 have swapped. When you compare this PCM’s fuel injector wiring diagrams for the Gen I small-block with the LS-series engines, you see something interesting: General Motors simply swapped injector outputs 4 and 7, and 3 and 2 within the engine wire harness to address the firing order change.

Is there an advantage of swapping? just too many questions on this....
In a car park around 20 years ago I heard someone say to someone else on his mustang with a windsor engine said he swapped two leads, thinking 4 and 7(was a long time ago) for a different sound.
 
I still have my old crank. I'm not going to swap the firing order, but just wondering if the pistons are in the exact same position, else surely it cant be possible to swap firing order.
 
Good explanation

 
Good explanation

Interesting article, thanks for posting that, that answeres a few questions. :p
 
Just watched an episode of engine masters where they did exactly this. The test mule was a BBC 572 and the results were negligible.
Cam swap required.
 
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