I have read that the reason that GM changed the firing order on their new engs
is it reduced torsional stress in the eng system by 15%
>
> From: "Dave Dahlgren" <ddahlgren@snet.net>
> Date: 2004/03/13 Sat AM 04:38:53 CST
> To: <richk@mercurylink.net>, <land-speed@autox.team.net>
> Subject: RE: 4-7 firing order cam swap
>
> Most Dynos are +- 1% at best not counting variatins in the cell during a
> test...
> 3-20 hp out of how much?
> If you swap 4 & 7 to eliminate the 5-7 combo of firing together you replace
> it with a 4-2 combo.
> In a 700 hp engine the best you can measure is +- 7 hp so 693 and 707 hp are
> the same number unless you make around 10 pulls and average them.
> I don't think you can have a 90 degree crank in a V-8 that does not fire 2
> cylinder next to each other..
> The only thing i can imagine you could do with this is swap some torsional
> twist in the cam for some twist in the crank.
> Next..
> Dave
> > -----Original Message-----
> > From: owner-land-speed@autox.team.net
> > [mailto:owner-land-speed@autox.team.net]On Behalf Of
> > richk@mercurylink.net
> > Sent: Friday, March 12, 2004 8:04 PM
> > To: land-speed@autox.team.net
> > Subject: 4-7 firing order cam swap
> >
> >
> > Twice I've run across this in the past month but haven't seen any
> > technical discussion on the subject. Swapping chevy firing order giving
> > claimed increase of 3 - 20 HP in a simple A - B cam comparison. What's
> > being gained here? How does exhaust or intake design affect this?
> >
> > RichK
>
"Sparky"
Lakester 2211
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