4 - 7 theory
#318883
05/15/09 12:35 PM
05/15/09 12:35 PM
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Joined: Apr 2007
Posts: 4,525 Daisyland USA
jnkgal
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Joined: Apr 2007
Posts: 4,525
Daisyland USA
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What is the rationale behind the 4 - 7 theory for the firing order. why do they say it runs better and what all do you have to do ( besides changing the plug wires) to make it sucessful?
thanks moports
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Re: 4 - 7 theory
[Re: jnkgal]
#318884
05/15/09 12:55 PM
05/15/09 12:55 PM
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Joined: Feb 2003
Posts: 12,675 Columbia, CT
moper
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There should be a bunch of ideas on this one. From what I know and I'm sure I'll be corrected here if I'm wrong, the differences are in pumping losses due to less crank deflection on the different crank throws. There are some builders who find power there, others who find smoothness within a certain rpm range. Some find nothing. I think a ton of the "found power" has to do with getting the precise cam to match the head and rpm combo. If that is not already perfect, I don't think you'll see a gain. Personally, I don't see much of a bonus in it and I never bothered. But, for some in certain circumstances due to class restrictions or whatever, they may find it helps. The only thing that needs to be changed is the cam from what I know. Which is arguably limited.
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Post deleted by Defbob
[Re: moper]
#318885
05/15/09 01:09 PM
05/15/09 01:09 PM
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Re: 4 - 7 theory
[Re: tjmarcus1]
#318887
05/15/09 03:07 PM
05/15/09 03:07 PM
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Joined: Dec 2006
Posts: 3,533 Indiana
Fury Fan
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Ford changed teh firing order on the EFI 302/5.0 in the mid 80s. The HO Mustang engine has a different firing order than the standard EFI engine.
Although the order is different than Mopar, you might be able to research the reasons behind that design change, might get some insight...
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Re: 4 - 7 theory
[Re: Fury Fan]
#318888
05/15/09 09:46 PM
05/15/09 09:46 PM
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Joined: Feb 2004
Posts: 6,257 acworth / N. georgia - south e...
cheapstreetdustr
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i dont see the big deal. its basic principal is the same as if you just turn the engine around ...other wise every thing else is the same. how could that improve hp or anything else.? cheapst.
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Re: 4 - 7 theory
[Re: cheapstreetdustr]
#318889
05/15/09 10:23 PM
05/15/09 10:23 PM
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Joined: Jan 2003
Posts: 20,179 Park Forest, IL
slantzilla
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David Reher stated that they did not do it for power, they thought reliability was better. I have a buddy at work with a 565 Schmidt motor that he paid for the 4-7 swap on. Motor never made good power and was in fact a pig, until he put the 4 and 7 wires in the normal place on the cap. Schmidt hosed him.
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