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WHat are the benifits of running a 4 7 swap cam in a big block chevy of 565 plus cubic inches.

Is there any more power to be found?
Is it less stress on the engine?
 

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Motorboatin SOB
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From what Ive read, it makes a little more power 'under the curve' and it idles smoother, putting a little less stress on the rotating assembly at higher RPM's.

Just what Ive read though, someone will come in with more knowledge on the subject than me.
 

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4/7 swap

Hendrick Racing, the Nascar team did some testing to find the best firing order possible for the engine packages, and found that the 4/7 swap was the best firing order, and it did smooth out the engine a little bit, and made a small amount of power more, but for us bracket racers, we would probably never ever feel the difference, and it can be measured on a dyno, but to not waste time doing it as it was already done.

Darin Morgan from Reher & Morrison found that it gave 4-6 hp gains in the 555+ cuin range with a single 4 barrel, and 6-8 with tunnel rams and the gains were accross the board in the curve. So, for another $30. you can have one, and for the difference, why not, it's only $30. more for a few more ponies!!!;) Nascar does NOT allow the different firing order, otherwise all the teams would make the switch over night to make that kind of gain.

Steve Schmidt was supposidly the first to find more power in this firing swap running NHRA engines. Info found in the Hot Rod Horsepower Handbook, white cover with a 572 bbc on the cover. $25. at Borders Books Hope it helps.

I run one in my 505bbc and it seems to be just as nasty as all the rest, but when I broke an oil pump pickup tube, when I pulled the pan, the rod & main bearings looked like brand new, very little wear with over 60 hard passes on it. My 2 cents worth.
 

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4/7

The Olds firing order smooths out the rev and idle of the cam, and generally most cam makers will tell you it broadens the torque curve a bit, as well as smoothing it out.
I run one in mine. Seems to work well.
 

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I have a comp cams 4/7 swap in our 556 BBC running mechancal injected methanol and that motor idles smoother then anything I have ever seen with a cam that has 290ish degrees duration @ .050 on 110 lc. That made a believer out of me.
 

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I don't think just sticking a 4/7 swap cam in is going to do much of anything... it's more about manifold and header design that will take advantage of firing order and intake pulses.... at least IMO.

But today the firing order swaps are so common that the cores available often have the swap already in them.... and I just get what's available. If 4/7 core is on the shelf, that's what I get. If 4/7 2/3 is on the shelf(ford, and LS firing order) then that is also what I get.

Ford firing order, 13726548 is the same as a chevrolet firing order with 2/3 7/4 swap 18726543.
 

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Chris you might be right, but my heads, intake, inductions system and headers were on a 502 with just about the exact cam without the 4/7 swap and trust me then I tell you this thing idles 10x smoother. Like your saying, being it is common I have not heard anyone find a negitive except some cam grinders charge more.
 

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I think the gain depends on the engine and all the factors as Chris said. Warren Johnson said that he has been doing firing order swaps since the early 70s.
 

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My take is if you need a new cam buy the swap cause it don't hurt but for the average racer it's not worth the cost/effort to change it. JMO, RM
 

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Chris you might be right, but my heads, intake, inductions system and headers were on a 502 with just about the exact cam without the 4/7 swap and trust me then I tell you this thing idles 10x smoother. Like your saying, being it is common I have not heard anyone find a negitive except some cam grinders charge more.

And that may be true. And it could also be true that something about the dynamics in your engine, likes the 4/7 swap....
 

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One other question isn

One other question while we are on the subject of 4-7 cam swaps. Is it the swap that makes the idle roll? I have noticed a vast majority of the cars with a 4-7 cam swap have an idle that rolls and purrs instead of being choppy. Kind of hard to describe, but I'm sure you guys have heard what I mean. It does that in my car also.

I know it smooths out the idle, but most of the ones I've heard roll like that.
 

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Hot rod did a test,:
http://www.hotrod.com/techfaq/113_0701_lunati_cams/index.html
They do add power and they sure idle better,I have one in my 565.
"Copied from Hot Rod Magazine"

That comment leads to James Humphreys at Lunati, who's adamant that the power gains are in the intake manifold. Many believe that the point of the 4/7 swap is to prevent cylinders 5 and 7 from firing next to each other and drawing too much from the same area of the intake and carb. However, a 4/7 swap puts cylinders 4 and 2 firing next to each other at the right front of the engine instead of 5 and 7 at the left rear, so what's the difference? Further, if you swap the order of cylinders 3 and 2 in addition to 4 and 7 to get the LS1 firing order, then it's 1 and 3 that fire next to each other. There's no way around it with an even-fire V-8. So the issue is not consecutive firing. According to Humphreys, it's the sequence and location of the pulses in the intake that change locations when you alter the firing order, and which cuts down on reversion.

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My Thinking is that taking the 2 cylinders that fire next to each other from the rear of the cam and moving them to the front of the cam reduces cam twist and improves cam timing accuracy.

The more spring pressure and more aggressive the cam, the more HP improvement. Notice that big diameter cam cores are becoming
more popular:rolleyes:
 
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