4/7 swap in firing order..

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Petzschler

Petzschler

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whats the advantage of the 4/7 swap in the firing order? is the advantage in the fuel distribution into cylinder #2? in the conventional firing order #5 and #7 pull fuel to the back of the engine and then #2 pulls to the front at the opposite end and gets lean. i was always under the assumption thats what dual plane (LD340 for eg) intakes were for. and staggered jetting usually solves anymore leaning out problems for that. i can see how the #2 going lean be a problem with a single plane intake and possibley the need for the 4/7 swap. what am i missing here? or is that swap just for a high rpm/ single plane/ tunnel ram kinda thing?
 
I'm not the expert to answer this, but, I heard it is a power finding effort discovered from racers. I also heard something about a smoother running engine. The effort is used with big single plane intakes and roller cams etc....
Also, how the fireing order is...example 5&7 next to each other.

Not so much mild dual plane intake builds.
 
I believe i seen this on Horsepower tv when they had a cam that had this done. it got something like 30 more HP
 
A friend of mine who races a Chevy powered 1/4 mile dirt track car in Antioch swears by this, says they pick up a few more HP. I believe even a few cam mfg's catalog cams for this. I've only heard this done on Chevys, nothing else. Interesting thought, though, they both use the same firing order.
 
Here's the best information we have at this time.
1)The advantage is in the fuel distribution onto cylinder #2. In the conventional firing order 5 and 7 pull fuel to the back of the engine and then 2 pulls to the front at the opposite end. This became a problem in BBC because the number 2 and 7 cylinder ports are long. 5 helps 7 pull to the back then 2 tries to pull forward and gets lean. You do not see this on 1 and 8 because they are short runners. By revising order (swap 7 and 4), 8 helps 7 and 4 helps 2. Thus, your fuel distribution is more balanced between cylinders.
2)Helps equalize EGT across the board.
3)Works best with 500+cid/7000rpm+ packages. +/- 1% on the dyno.
4)Reduces crankshaft deflection (jurys out on that one)
5)Has been used in Cup/Busch/Craftsman but unconfirmed information has it that it has been outlawed, stock firing order only now. Don, perhaps your contacts can shed some light on that.
6)I have information that some restricted intake class builders have had very good success with the 4/7 cams. That seems to go against the grain but I have heard it from more than one source.
7) Flatter torque curve.
A few points for discussion. Fire away.
 
I remember some where a BB MoPar did this. I know it's been done before.
 
I have always heard it was for the crank harmonics. I've not heard about the a/f bit but that sounds very possible however on many engines witha signle plane, especially race (single plane) stuff, the varience in outboard cylinders is very small. Under a couple inches in port length anyway. I know it helps get rid of the crank stress at high rpm. But it'snothing I'd ever really consider. I also believe some opf the fastest FAST cars use that swap. They have to use factory dual plane manifolds so the mixture deal makes more sense.
 
Dudek's 10 second FAST road runner utilizes the 4/7 swap.
 
moper said:
I have always heard it was for the crank harmonics. I've not heard about the a/f bit but that sounds very possible however on many engines witha signle plane, especially race (single plane) stuff, the varience in outboard cylinders is very small. Under a couple inches in port length anyway. I know it helps get rid of the crank stress at high rpm. But it'snothing I'd ever really consider. I also believe some opf the fastest FAST cars use that swap. They have to use factory dual plane manifolds so the mixture deal makes more sense.
Click to expand...
i didn't even think of looking at it from a harmonics point of view. i guess it would even out the powerstroke pulses. that probably would have a significant impact on bearing life i would imagine. i would also guess the engine will be willing to rev more freely with the 4/7. kinda opens up the bottle neck effect in the intake charge of the 5/7 cylinders in a dual plane layout. if that makes sence. good info. thanks moper.
 
4-7 is worth 10 hp in a Chev circle track engine...definatly sounds different...sounds like a ford.
Haven't bothered to grind up a couple of RB cams to see how the chry eng responds to a direct compairson...
I have a 4-7 in my 830 hp low deck...nothing surprising jumped off the page that I would attribute to a 4-7 swap.
 
On the intake side of it, it's all chevy related, or a specific intake design flaw remedy, if even that. I even ``kinda doubt that idea, but would need to look at the intake design of the engine in question that supposedly picked up power from this.

Otherwise it's a main loading issue, more evenly distributes load to the mains, which I wonder if torsioning comes into play, 454's can toss rods like it's going out of style.

You know, this was the same thing TK/dodgeTKboy78 asked on moparchat.
And he was banned there, now A-BOMB360 is asking the same.
:read2: http://www.moparchat.com/forums/showthread.php?t=115062
u 2 are never on at the same time?
Just a coincidence I noticed, sorry If I distract from this awesome topic.
 
A 180* header would help scavenge, I mean if you're considering a 4/7 for 5-10 hp, then this would be business as usual, right?

BTW Do you still have that 4/7 swap cam dodgeTKboy78?

I remember you telling us you had a 4/7 swap cam that was Identical specs to your .480 cam[or whatever it was]:read2:

Is it a dual plane intake on your motor?

You've been curious about this for a while, why not just try it and see if you can feel any diff.
I say if you can't feel even the slightest increase then it's not enough to make it worth while on a street engine.

you guys have with this.8)
:read2: http://www.moparchat.com/forums/showthread.php?t=115062
 
Rob R said:
...I have a 4-7 in my 830 hp low deck...nothing surprising jumped off the page that I would attribute to a 4-7 swap.
Click to expand...
whats your reason for the 4/7 on the low deck. after reading alot about this, i'm starting to understand the fundemental principles of why the 4/7 is a good idea. i'm also staring to think its a combination of parts. intakes obviously, evening out of crankshaft harmonics, and i'm betting Rod/Stroke ratios has ALOT to do with it. this is all just a guess tho. no harden facts to back it up other then it does seem to make more peak and under the curve horsepower on some engines.
 
A-BOMB360 said:
i was thinking about that too. then i realised with the change to the 1-8-7-3-6-5-4-2 firing order, it puts #2 & #4 next to eachother. so really whats the difference? i dunno.
Click to expand...

I'm going to guess it deals with exact placement within the single plane intake would be more desireable. Not so desireable is the number 5&7 in asingle plane for us. Swap 4 & 7 around. Whatcha get.
(Under the weather and the brainis off)
Also the Harmonics like MoPer mentioned. I did here something about that a way's back, BUT, IDK crap!

W&CGuy;
You know, this was the same thing TK/dodgeTKboy78 asked on moparchat.
And he was banned there, now A-BOMB360 is asking the same. u 2 are never on at the same time?
Click to expand...
TK was banned there? LOL, well, TK and A-bomb 360 IMO, aren't the same guy. I was tinking you and him were the same guy creating a whirlpool in the pot for fun. Ha ha ha ha ha
Just a coincidence I noticed, sorry If I distract from this awesome topic.
Click to expand...
Just me. Good laff, good one though. Say! Where the heck is TK Anyway? I know heres here under a different screen name but hasn't made a apperance in a bit. I figured he'd be here with this topic.
 
Well I know all the pro stock engines do this. Probably all the comp and SS guys as well but is it worth it for a street engine or a bracket engine? Probably not unless you are scratch building an engine anyway. In a small block I think the 48* tappet angle is worth more than the 4/7 swap but if you are custom ordering a cam anyway, why not go for it. I wouldn't swap cams in a running engine for that reason alone.
 
1wild&crazyguy said:
On the intake side of it, it's all chevy related, or a specific intake design flaw remedy, if even that. I even ``kinda doubt that idea, but would need to look at the intake design of the engine in question that supposedly picked up power from this.

Otherwise it's a main loading issue, more evenly distributes load to the mains, which I wonder if torsioning comes into play, 454's can toss rods like it's going out of style.

You know, this was the same thing TK/dodgeTKboy78 asked on moparchat.
And he was banned there, now A-BOMB360 is asking the same.
:read2: http://www.moparchat.com/forums/showthread.php?t=115062
u 2 are never on at the same time?
Just a coincidence I noticed, sorry If I distract from this awesome topic.
Click to expand...

Justin, don't start your bullshit again, we all know your the only one who has multiple personalities........ (And you are also a piss poor detective)

FYI...... I quit going to Moparchat, and, look what happened. That place has gone so far down hill.... I actually had no idea I was even banned, I tried to log in, here's what I got....

You have been banned for the following reason:
You chose to leave
Date the ban will be lifted: Never
Click to expand...

LOL, what a joke that place is......... The Dick and Stoga show. (Talk about immature)

Back to the topic, yes, I do, from what I gathered, on a Mopar, at least, it is more of a smooth power, and more power at lower speeds, from the even (ish) distribution. Circle track guys seem to like it for the smoothness in power to the wheels. I think, 1wildandcrazy was a part of that thread, maybe? (badassington/passingyou/whothehellknowswhatusername) I think everyone came to the conclusion that it will do slightly more than make your Mopar sound like a 427 Ford...... :read2:
 
That response I expected, yea....

How bout PM's from here out so another thread isn't destroyed.


BTW ANOTHER MEMBER ASKED DICK AND HE SAID YOU WERE BANNED FOR ARGUING AND ACTING LIKE A JERK, THATS A REAL SHOCKER.....

you rallied to have me banned and then after was banned yourself cause your sht didn't stop.
So basically you took away from the sight, so the site dropped you.

have a good one, and right back at cha!
 
dodgetkboy78 said:
I await my PM...........
Click to expand...

WOW you are a child

whats the deal with you?

Your mouth outruns your brain x10

Your goal is to be the guy responsible for the hung jury, and posts are counterproductive.

Your opinion 85% of the time contradicts all others along with even reality sometimes.

AND you're arrogant about it to boot!

And guess what? no, I nor anyone else wants any fries with what ever the hell it is you are attempting to serve.


Just be cool to others, ya know... a human being?, you are not even in the top 20 people I would take advice from and most here agree with me on this.ENOUGH
 
You should erase your post, your screwing up the thread now........ Picking a battle your sure to lose.

If you read the thread from Moparchat, you will see the conclusion me and wildandcrazy (Passingyou in that thread) cam to...... Ahhh, it was nice when he was civil. Justin has been so nice and squishy lately... Hope he doesn't change......

Still no PM.
 
Even tho me and Abomb have gotten into it a little tiny bit, over the 302 head thread you and him killed, I see no reason why this thread was dead, he asked a legitimate question, one I never really got a solid answer as to what it would DO........ I HAD the chance, but just didn't feel like trying, and now that my motor is solid, will never know.

I think it is a good topic......
 
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