Firing order - any variations?

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paulclark

paulclark

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Do all mopar V8s have the same firing order?
Specifically engines of the 60s - 90s, and their successors today. I assume all of a type are the same - LA, RB, etc. Or are there variations? Do any of the modern mopar engines have a different firing order than in the muscle car days?
 
Yep , Most v8s from the 60s had 18436572. Fords were different. Ford doesnt number the cylinders the same either .
 
18436572.
Every Mopar V8 from '50s polys to Hellcats.
A, LA, B/RB, Magnums; early, mid and late hemis; and 4.7s included.
Also applies to GMs and Fords (with the exception of the 351 Windsor- 13726548)
Note: With most Fords, the 15426378 firing order appears to be different, but it's actually the same as Mopar/GM. Ford just designates the cylinders differently, placing #1 on the front right instead of front left, and works rearward sequentially instead of alternating banks.
Mopar/GM
1737660816110.png

Ford
1737660781069.png
 
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Daves69 said:
Exceptions might be reverse rotation marine engines.
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Or big block Mopars. (Distributor in the front and passenger side. Opposite of small blocks)
 
I have heard older NASCAR engine builders talk about getting cams ground to different configurations and changing the firing order around. It made a significant amount more horsepower (don't ask me how, cause I have no idea)......and they never got caught. Nothing in the rule book against it either, at the time.
 
JDMopar said:
I have heard older NASCAR engine builders talk about getting cams ground to different configurations and changing the firing order around. It made a significant amount more horsepower (don't ask me how, cause I have no idea)......and they never got caught. Nothing in the rule book against it either, at the time.
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Yes, the 4/7 swap was popular on Chebby small and big blocks in NASCAR and Prostock, claimed it helped fuel distribution and main bearing wear.
 
JDMopar said:
I have heard older NASCAR engine builders talk about getting cams ground to different configurations and changing the firing order around. It made a significant amount more horsepower (don't ask me how, cause I have no idea)......and they never got caught. Nothing in the rule book against it either, at the time.
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Professor Fate said:
Yes, the 4/7 swap was popular on Chebby small and big blocks in NASCAR and Prostock, claimed it helped fuel distribution and main bearing wear.
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The 4/7 swap has been tested.
(I have no info relating to Nascar or prostock), but the testing I've seen on very potent street/strip engines showed almost insignificant power differences.
Whether it helps fuel distribution or bearing wear or not,.... I don't know.
 
Yup. All the same, even marine engines. Although some are reverse rotation, they still fire in the same order.
 
JDMopar said:
I have heard older NASCAR engine builders talk about getting cams ground to different configurations and changing the firing order around. It made a significant amount more horsepower (don't ask me how, cause I have no idea)......and they never got caught. Nothing in the rule book against it either, at the time.
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Cranks were ground different also.
 
The first 4/7 swap I read about was Colman Roddy in his Comp Eliminator Corvette.

That had to be in the early 1980’s when it was published so he probably was using the 4/7 swap a year or so (at least) before it was published.

I’m also fairly certain he wasn’t the only one testing it.


I have done many 4/7 swaps (any time I can get a 4/7 swap cam core I do it) and several 4/7-5/2 swaps (I think it’s 5-2…it’s actually an older Cadillac firing order) when I could find those cores.

Sometimes we saw nothing for power. Sometimes we’d see 7-8 hp. The higher the rpm the bigger the power increase.

What happened every single time was a noticeable and I mean noticeable in the way a simple minded dolt could tell and that was these engines were always much much smoother.

If I have the option for a firing order change I 100% do it 100% of the time.
 
The 4/7 swap that GM put in to production on all LS engines was done (according to a gm engineer) because it transferred the stress from the number one main to the number 3 main. Or something like that. As far as power is concerned, every time I’ve seen it tested it hasn’t resulted in much power. On big HP bbc stuff I think it’s a couple hp here or there. On smaller hp or smaller cube stuff it’s negligible.
 
I run a 4/7 swap. Hence my carb cap just as a reminder... Yes, it does make a difference. Especially, at high ram's for long durations of time such as NASCAR and Off Road truck series engines. We do alot of 4/7 & 5/2 swaps as mentioned above, when cam cores available allow it. Especially, in alot of LS stuff we do.

rsz_20160414_201144.jpg
 
6PKRTSE said:
I run a 4/7 swap. Hence my carb cap just as a reminder... Yes, it does make a difference. Especially, at high ram's for long durations of time such as NASCAR and Off Road truck series engines. We do alot of 4/7 & 5/2 swaps as mentioned above, when cam cores available allow it. Especially, in alot of LS stuff we do.

View attachment 1716357600
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OUTSTANDING!!!!!!!!!!!!!!!!!!!!
 
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