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Author Topic:   4/7 Swap Cam
HERNDON
Dirt Full Roller

Total posts: 73
posted June 23, 2005 04:48 AM  
Can someone tell me what I need to know about a 4/7 swap cam? Advantages, disadvantages....what i need to know to build a 377 roller using one?? I've heard it's the way to go, and that it needs a lot of gear, but that's all I know....Thanks

nmracer
Dirt Full Roller

Total posts: 30
posted June 23, 2005 06:53 AM  
I am not sure that you really need to pour the gear to it,we have one in a 355ci.and it pulls great.I have seen two idenical engines dynoed one with the 4/7 swap and a reg. cam,both rollers and the 4/7 made more power.Don't remember exact numbers.Bottom line IMO its better.

52mod
Dirt Roller

Total posts: 11
posted June 23, 2005 06:58 AM  
The 4/7 is barely noticeable on a dyno from what I've seen and probably not worth the extra money paid for the cam. It does respond better to large cubic inch engines(excess of 500")and in theory smoothes out firing sequence and fuel flow by reducing intake reversion. I have yet to see where it's made any significant improvement but would love to see dyno sheets to support this.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 23, 2005 08:17 AM  
I dont know that you need to gear it any differently than a standard order cam. There may be a small increae in power but likely small enough you wont feel i in the seat of you pants. From what Ive been told the main benefit is it eases stress on the crank. I prob wouldnt go and spend a bunch of money just to get one, but if you are getting a new cam anyway and want to try it go for it. Just remember its not legal in IMCA.

zeroracing
Dirt Forum Champ
Total posts: 1875
posted June 23, 2005 08:33 AM  
The main benifits to one is that it is supposed to smooth out the powerband, not really top end power. The 4/7 swap cam is supposed to smooth the low to mid range torque. Also i have heard it MIGHT add a few hp at very very high rpms, and i have heard that it is less wear on the crank.

devil wrench
Dirt Maniac

Total posts: 178
posted June 23, 2005 09:52 AM  
Just like dirtbuster said... they're made to reduce harmonic stresses on the crank. They smooth up the idle too. As for gearing, it doesn't change a point.

nmracer
Dirt Full Roller

Total posts: 30
posted June 23, 2005 02:10 PM  
As i said I don't remember exactly but it was like 10-15 torque and 15-20 hp.

HERNDON
Dirt Full Roller

Total posts: 73
posted June 23, 2005 04:14 PM  
Does anyone run one, or are these just opinions?? I'd like to know if a driver can notice the difference, say if one weekend you ran it, and the next you didn't.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 23, 2005 04:33 PM  
If all you did was swap cams and keep everything else the same, I would have to say no you wouldnt feel it.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted June 23, 2005 07:34 PM  
I talked with Comp Cams recently about this. Here is exactly what they said about them. "The 4/7 swap cams have helped smooth out the delivery of power along with lower motor temps by about 10-15 degrees. They have also seen power increases in the 8-15 horsepower range. So I think you will see some improvement over a standard firing order cam with the 4/7 swap cam. "

Hope that helps!!

iowatoolman
Dirt Freak

Total posts: 369
posted June 23, 2005 07:58 PM  
i buy my cams from chet herbert cams they told me that it wasn't worth the time to change "the guy i buy from told me that he did it to his 547 cid motor and it made no more power than before"

NOT WORTH THE GASKET KIT TO CHANGE


drive hard or drive home

Mr. Badboy
Dirt Full Roller

Total posts: 29
posted June 23, 2005 10:12 PM  
We have a 4/7 cam in our car, having changed from the normal firing order for the past 5 years. Based on dyno results, the normal firing order and the 4/7 produce about the same power. We chose the 4/7 because this was the only firing order available for our grind.

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 24, 2005 07:29 AM  
Same power ok, but does it feel smoother in the car, less heat, any advantage at all?

Its not all about the power. If it would improve drivability, and smooth out the power band of a 23* engine it would be worth it.

There is a company, i'll try to find the name but they make a 4/7 swap with a 2/3 swap. 4 cyclinders swaped. LSM cams i believe the name was.
http://www.lsmeng.com/

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted June 24, 2005 07:41 AM  
Depends on who you talk to. Cam grinders will prob tell you it will increase HP and they are prob stretching it to say 15HP, but they need to sell cams. Most engine builders will prob tell there is no HP difference worth noting, but it prob does reduce stress on the crank and possibly make it smoother. Again is it enough difference that you would notice it int he car, in my opinion..no. IS it worth changing the cam just to get the 4/7 swap..no. If you want to play with it or have to get a new cam then its up to you, but it will cost you more than a standard cam as well if I remember right.

GRTWallbanger
Dirt Maniac

Total posts: 196
posted June 24, 2005 10:19 AM  
Does anybody know if there is a production car with this 4/7 swap?I thought maybe the new corvette has it?If it does then it would be legal in IMCA.

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 24, 2005 10:57 AM  
I believe, and dont quote me on this, but the reason for the swaps on the SBC is to make the firing order more like the Ford. Evidently the Fords firing order is the optimum for crank life and even cylider firing / filling.

Thats a good point Dirtbuster, i would like to hear from some drivers who run the 4/7 swap to see if there actually smoother or is it all just hype. Probaly hype but i would like to hear some drivers opinions.

Next year, i want to switch cams, wanna lower the duration and bring the power band down a little. Plus were running a regrind, small bas circle roller and i want to replace it with a non small base circle cam. So i would like to make a decison one way or another.

graham cook
Dirt Roller

Total posts: 7
posted June 24, 2005 01:08 PM  
Went to the 4/7 swap a few years ago first thing I noticed was how well it idiled and worked at low rpm for a large hp motor.

Kromulous
Dirt Forum Champ
Total posts: 796
posted June 24, 2005 01:17 PM  
How is it on the track? any smoother on the power, in the power band?

Krom.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted June 24, 2005 01:53 PM  
The 4/7 swap is nothing new, it started in drag racing with fords in the 60's. We ran one several years ago only because we bought a used motor that had one in it. Driver didn't think it was any better/worse than a standard cam. We ended up swapping it out for a Crower. A few of my friends switched to them this year thinking that they were the new hot ticket, everyone of them says that there isn't any seat of the pants difference.

The big mystery is why a 4/7 swap cam costs more?

[This message has been edited by wfoondirt (edited June 24, 2005).]

nine finger
Dirt Forum Racer

Total posts: 76
posted June 26, 2005 05:49 PM  
take seven dollars out of your pocket i will give you four dollars back and thats what it is worth.

David Blue 22
Dirt Roller

Total posts: 6
posted June 26, 2005 09:13 PM  
I had Howards Cams grind a cam with the regular firing order. The profile I wanted was only offered as a 4/7 swap cam. The person that took my order said hmmm we have never done this one before. Anyway, it runs pretty strong so far.

iowatoolman
Dirt Freak

Total posts: 369
posted June 27, 2005 09:16 AM  
now that is what you call the 7/4 swap good one "nine"
quote:
Originally posted by nine finger:
take seven dollars out of your pocket i will give you four dollars back and thats what it is worth.


iowatoolman
Dirt Freak

Total posts: 369
posted June 27, 2005 09:19 AM  
if any of you have paid attention if you notice a 302 and a 351 run a different firing order and you can put a 351w cam in a 302 you just have to change the firing order too LOL them cam grinders are getting the fat end of this rumor about swapping cylinders


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