Chevy 4 & 7 Swap Firing Order - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-03-2005, 09:24 AM
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Chevy 4 & 7 Swap Firing Order

These cams provide an exceptionally smooth torque curve and a significant decrease in crankshaft deflection.
The 4 & 7 swap firing order cams have been dyno and track tested in a variety of applications. Customers have reported an increase in horsepower over traditional firing order cams.

Thats the message from Comp Cams.

Fact or fiction ? How is the induction and exhaust systems effected?

Anybody got any good theories or opinions on this subject.

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Old 02-03-2005, 09:27 AM
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I know thats an old trick. But I would think if it was really that great we would be seeing alot more of a cam selection with a 4/7 switch.
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Old 02-03-2005, 09:41 AM
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I like the idea. The vortec heads are prone to cracks and it happens between the 5-7 cylinders often. This is b/c they fire one after the other creating a lot of heat in that area of the head. Also the intake runners are side by side and must draw against each other to some extent.
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Old 02-03-2005, 09:45 AM
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Changing the firing order didn't help any on a street/strip type engine. Some rag did a test and the dyno showed no measurable gains or change in the hp/tq curve.

Maybe it works for some folks with the resources to take advantage of it but most of of wouldn't gain a thing from doing that. They did say that the engine seemed to run a bit smoother, whatever that means.

Larry
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Old 02-03-2005, 10:27 AM
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I've tried them before and found nothing. Engine felt smoother with less vibration but he differences were negligable. Not to be confused with smoother application of power.
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Old 02-03-2005, 10:55 AM
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http://www.motorsportsnxs.com/ohmy.gif

Or has anything really changed? Cylinders 4-2 now show the same problem.lol

Last edited by NXS; 02-03-2005 at 11:01 AM.
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Old 02-03-2005, 05:41 PM
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Ford did the same thing with the 302/5.0 change. The 351W also uses this "revised" firing order.

I put a 351W cam in my old 5.0. All you have to do is change the plug wires to match. The new cam was bigger, but I didn't notice any "magic" with the change.
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Old 02-04-2005, 05:05 AM
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cam swap

There is no silver bullit here... You now have cylinders 2 and 4 firing in sucession..... In any engine the average person would build there will not be any difference in hp..

There is a theory that in some of the larger CI engines that are at the end of the rope for finding HP the swap helps with the intake pulses and makes a tad bit more HP. But like the long connecting rod issue i have never seen real world numbers proving this....

Keith
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Old 02-04-2005, 06:22 AM
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I would have to guess that if there were ANY advantage to swapping the order, the CUP teams would be doing it. In the racing forums I follow the topic has come up several times with the same result ... they tested and got no improvement.
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