modified firing order big block

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fearsomepuller

fearsomepuller

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What do you think of changing the #4 and #7 firing order? I am building a 512 for my Duster and thought now is the time. Hard to find much info on this.
 
There is some merit to the swap - provided you use it in the rpm ranges where it might help. My understanding is not complete on it - but it seems like it reduces the harmonics and pumping losses from the opposite cylinders firing. In doing so it frees up a little power. I know the FAST guys use the swapped order. I can't say as it's worth a ton of power - but because it's "free", meaning you're simply reducing the parasitic loss, you don't have to make more power to get the bonus of having it at the tires. I'd suggest you post over at Speedtalk.com - there are pros there that make use of that swap.
 
In search of power, I'd guess..

One of the Nascar engine builders tried messing around like that,, they had the weirdest sounding exhaust,, You could tell them by the sound..

They (who-ever) went back to conventional, so it couldn't have worked all that well..
 
Is it accomplished with just a plug wire change or......does the cam need to be ground to match it?
 
I believe I read that top fuel teams change the fireorder to go faster.
 
There is power to be found in the swap. Moper hit it on harmonics and a smoother running engine is a result. Of course the cost is a bit high to do this with the crank for starters and then the cam for seconds. After that, there is no extra cost. But a bit pricey it is.

I would have to give this expense a want to do or a must for the true all out race teams, like the above mentioned. The teams were every last once of HP is being hunted regardless of cost. After all, your chasing the money. BIG MONEY!

"I'll never go there myself unless I win a record setting Mega Millions all by myself."
 
I have to admit this is a subject I don't really understand. The 302/ 351 Ferd is a good example.

It would seem to me that IF the intake is properly designed, and IF the exhaust system is properly designed, there would be no power gain from either method. Remember "back when" some guys were experimenting with 180* headers?

(You just THOUGHT Hedmans were hard on the ground LOL)

dougs-headers-a.jpg
 
I agree 67 - but we have to remember that no induction or exhaust is perfect due to packaging. The benefits from fuel distribution are a small proportion of the increase. The rest coming from the reduction in crank twist and harmonics. We're talking about gains of 1/2 to 1% from it... Not huge figures. I could see where a restricted class might benefit - like the FAST guys, or 2bbl short trackers, etc.
 
Thanks for the article. I had forgotten than GM went to this, so this means that the newer Ferd 351, the newer GM LS, and the modified Mopar firing order is in fact the same. I'd sure like to see something besides HRM, though LOL
 
2 cylinders on the same side firing and then 2 cylinder firing on the other side? Am I understanding this right
 
67Dart273 said:
Thanks for the article. I had forgotten than GM went to this, so this means that the newer Ferd 351, the newer GM LS, and the modified Mopar firing order is in fact the same. I'd sure like to see something besides HRM, though LOL
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I agree on the HRM :icon_smi:. I found it interesting that the guru's later in the article had no concensus as to if and why it worked...lol.
 
DobaDaddy said:
2 cylinders on the same side firing and then 2 cylinder firing on the other side? Am I understanding this right
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Hey Chuck. Some seem to think that the dificiencies in the intake design can be manipulated with the firing pulses, but even when a totally symetrical intake is used, there still is no concensus. Mostly it's just giving me a headache......lol. Think i'll just watch everyone else play with the idea.
 
So I guess the answer is 8 individual carbs / injector barrels and zoomie headers!!!
 
moper said:
Wasn't there an early Hemi that had that? Had these huge trumpets on the exhaust...lol
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Not factory. You are probably thinking of the old Mopar "High n Mighty."

mopp_0702_16_z+26th_annual_mopar_nationals+high_and_mighty_recreated.jpg



Any engine can be set up with something like dual throat webers, that is if you can get an intake or build one to fit them---- to provide a barrel for each cylinder, and nowadays, some are modifying older Hillborn/ Enderle injection for EFI. That with individual header tubes in effect creates 8 separately tunable independent engines, but of course exhaust systems are a "little tough" and many race classes require collector headers and or an exhaust system.
 
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