#4 and #7 firing order swap

[oldred95]

HPTV just put a four seven cam into a small block race motor using the exact same specs as a regular firing order cam and made an extra 32 HP simply by switching the #4 and #7 cylinders firing order. They said the cam costs an extra 90 bucks but for that kind of gain out of just changing firing order I'd say its well worth it. Has anyone done this swap before and have any first hand experience with it?

[mcnulty1]

I wonder if I could do that with an '01 Sierra, 5.3

[89stroker]

no you can't do that on the 5.3 because it doesn't have a distributer.

[domestictuner]

no you can't do that on the 5.3 because it doesn't have a distributer.
you could re-wire the coil boxes

[1500chevy5.7l]

so you can just swap the firing order of 4-7 how does that help?

[oldred95]

so you can just swap the firing order of 4-7 how does that help?
They said the cam manufacturer couldn't exactly explain the phenomina but they think it has something to do with creating a more equal balance of incoming air and fuel into the #4 and #7 cylinders or something along those lines.

You would think it would cause a miss fire or something but apparently not. Now that I know about this I'm going to check into it some more, if I can email that cam manufacturer and see what they can tell me and if this mod works for only NA applications or boost or anything in general.

[red4x4chevy]

You can not do that to a 5.3 because they have a new firing order. On anything on the street it will not really help with power a huge amount, but maybe up to 15 or 20 horse max. It will however create a smother powerband and help the crank last longer it helps to keep the loads on the crank down by changing thoose two cylinders firing order.

[fastredgmc]

how much power did this engine make?
Thats a big increase i could see if it were a 1000hp engine but anything else i cant see a increse like that. I know a guy that put one in a 500hp 406 and didnt notice a thing. Also herd of many dyno runs with nothing more than maybe 5 hp difference. They tell you anything on TV or magazines just make the advitiser happy

I think the ls1 engines aleady have that firing order.

[oldred95]

how much power did this engine make?
Thats a big increase i could see if it were a 1000hp engine but anything else i cant see a increse like that. I know a guy that put one in a 500hp 406 and didnt notice a thing. Also herd of many dyno runs with nothing more than maybe 5 hp difference. They tell you anything on TV or magazines just make the advitiser happy

I think the ls1 engines aleady have that firing order.
It was a 406 small block running AFR heads and 9:1 compression on 87 octane and it made 495 HP and 500 ft lbs at the crank on the engine dyno. After the cam swap HP was was 527 IIRC and I don't remember the torque.

[thegreat1]

do you guys think an engine without the cam will still run with the 4-7 wire swap. ill be the guinea pig and try it on my truck to see if anything changes!

[horsepwraddict]

it just balances things out so certain cylinder aren't 'fighting' each other, makeing more smooth power. It doesn't cause a misfire because you just swap the plug wires on the dizzy...even alot of the racers dont use it, thats saying something when the guys who will do anything to get every last ounce of power out of a motor dont beleive in it.

[horsepwraddict]

do you guys think an engine without the cam will still run with the 4-7 wire swap. ill be the guinea pig and try it on my truck to see if anything changes!

prob not. vavles wont be times correctly

[oldred95]

I might go swap wires for the hell of it. But if all you have to do is swap wires then where does the different cam profile come in. This chit gets confusing as soon as you start to actually think how it works.

[horsepwraddict]

I might go swap wires for the hell of it. But if all you have to do is swap wires then where does the different cam profile come in. This chit gets confusing as soon as you start to actually think how it works.

because the plugs will be firing on the wrong strokes.

[blu92]

no, it won't run right. Stop and think about it for a minute. You need to change both the cam and the dist. firing order. Hot Rod mag. did a story about it a while back. As I recall it did make some horsepower, but only on certain combos and it def. didn't make any difference for the street. My $.02

[oldred95]

I can't even find the cam manufacturer on the good old powerblock website. They said it was Laser something but thats all I remember. I'll try to remember and watch it again tomorrow to get the name of the place.

[WildmanZ28]

Any cam manufactuer can grind you a 4-7 swap cam. I've heard of it done on SBC's & BBC's. I'd like to see how it works in a more mild, "street" application. I have a feeling it wouldn't be worth it, and am curious about the idle quality.

Does anyone else remeber the odd fire & even fire Buick V6's? I do, the odd fire ones ran rough compared to the even fire motors.

[TITANIUM]

So this was just a wire swap. Same ole cam?

[cooker2003]

Those cylinders will not even fire if you only swap the plug wires. There is no reason to try it. You have to swap the cam along with the firing order.

[WildmanZ28]

So this was just a wire swap. Same ole cam?

No, it's both. Think like an 80's 5.0L, the non-HP had a std. firing order, and the HO motors have a 351W firing order. The cams match the firing order on the distributor. Otherwise you'd have cylinders firing and nothign in them to burn, and cylinders not firing with fuel being dumped into them.

[TITANIUM]

No, it's both. Think like an 80's 5.0L, the non-HP had a std. firing order, and the HO motors have a 351W firing order. The cams match the firing order on the distributor. Otherwise you'd have cylinders firing and nothign in them to burn, and cylinders not firing with fuel being dumped into them.
Gotcha!

[oldred95]

If it gives those two cylinders a more balanced air flow or whatever they said it did wouldn't that make for a smoother idle? My thinking is if it doesn't work then cam company's probably wouldn't be offering a cam grind for this setup. I wonder what it would do to the sound of the engine.

[jeep45238]

Only reason why I've heard of people using them is for some better idle qualities when running a huge cam.

[gabb1z]

HPTV just put a four seven cam into a small block race motor using the exact same specs as a regular firing order cam and made an extra 32 HP simply by switching the #4 and #7 cylinders firing order. They said the cam costs an extra 90 bucks but for that kind of gain out of just changing firing order I'd say its well worth it. Has anyone done this swap before and have any first hand experience with it?
That is an old show, And that only works on a Carbeurated engine and no computer. I had that on my 70 Elco, and you couldnt tell the difference?????????

[va454ss]

And that only works on a Carbeurated engine and no computer.

Why :think:

[Fast305]

Why :think:

It would work on TBI engines too. It makes more of a difference on engines with single plain manifolds. The firing order change keeps 7 from drawing in the partial intake charge left over after # 5 gets its share.

1-8-4-3-6-5-7-2.

vs.

1-8-7-3-6-5-4-2

[kylersaulsbury]

yeah if you just switch your wire its not going to run right, and will eventually burn up your pistons. it also won't change idle lope or anything unless you change the duration of the lobes. the cam they used was a straight 4/7 swap, with the same specs as the stock cam. Plus you have to keep in mind that was hp at the crank you figure in the 20% drivetrain loss, so you are looking at a 25.6 increase in hp. so its slightly noticable but not grab you by the seat of your pants.

imo if your getting a custom grind cam go ahead and throw in the swap but otherwise its not really worth the work.

[oldred95]

That is an old show, And that only works on a Carbeurated engine and no computer. I had that on my 70 Elco, and you couldnt tell the difference?????????
Right. It was just filmed in their new shop with their new above ground chassis dyno and showed the installe of their new engine dyno, none of which they had in the old shop except the old below ground dyno jet.



imo if your getting a custom grind cam go ahead and throw in the swap but otherwise its not really worth the work.
Thats what I'm thinking.

[billvill]

just changing the spark timing between 4 and 7 will do nothing more than make your truck misfire and idle poorly. If you wanted to change the firing order you would have to do it via a cam change. This idea has been around for a good ten years. I am not sure why this phenomenon works but it does. I do not believe the 34 hp gain claimed in the article you read. From everything I have read and heard it does yield about 4 to 7 hp at high rpm on a maximum effort race motor aka pro stock. It is not a practical modification on a street car oops I mean street truck.

[frank88chevy]

YEA courtney said so

[oldred95]

YEA courtney said so
I think Courtney and Jesse need to make a porno and make it available for download.

[Blad]

i just tryed this and yeah, it ran pretty ****ty

[jeep45238]

Genius, you've gotta swap cams to do this, not just the plug wires.

Some folks.....really need to go pay attention while they're in school....

[95nProgress]

no, it won't run right. Stop and think about it for a minute. You need to change both the cam and the dist. firing order. Hot Rod mag. did a story about it a while back. As I recall it did make some horsepower, but only on certain combos and it def. didn't make any difference for the street. My $.02

:word:

I always heard that you have to change the cam to do this. Look in Summit and Jegs and they advertise it something like "The new order in cams".

Brian

[Blad]

Genius, you've gotta swap cams to do this, not just the plug wires.

Some folks.....really need to go pay attention while they're in school....
well, "genius" it was worth a try. i had read about this in an old truckin magazine and now that it got brought up again i wanted to try it out. wanna drive my truck for me too?

[WhiteLightnin]

Not trying to crash the party but we ran that setup on our late model dirt car for a year and didn't notice any difference. Technically it wasn't "legal" for the track but the engine sounded the same and no one took notice. I'm sure if it had benefits as far as mileage and power go GM would have changed the firing order a long time ago.

[91s104x4]

I think Courtney and Jesse need to make a porno and make it available for download.

:hump: :hump: You know it!!!

[Busted Knuckles]

I gotta call BS on HPTV. I've seen back to back tests on 565 inch race engines and there was less than 10 hp gained. Not 10% mind you, 10 horsepower. It makes an engine run a little smoother and helps with scavenging a bit so this shop still uses 'em on most of their engines. There are gonna be a lot of pissed off folks who swap cams in a smallblock looking for 30hp and end up with no noticeable or measureable difference. And charging $90 extra is totally bogus. This is a popular enough swap that the blanks cost the same as standard firing order blanks, they're just sticking it to the consumer because it's the newest trick out there. Ever since Comp started making hydraulic roller cams on cast iron cores, I dropped 'em and started using either Crane or Lunati or having mine custom ground.