just watched horsepower tv

JACKO

JACKO

Club Member
and they engine dynoed a sbc 406ci i think it made like 470ish HP
then they put a laser cam it that changed the original sbc fireing order..basicly swaped the #4 and #7 fire...and it gained 30+hp...please someone explain this a bit more...:dontknow:


JACKO
 
Basically, the 4-7 swap is thought to increase the engines ability to draw
air into the cylinders with less cavitation to the intake charge. More air into
the engine = more horsepower produced.
 
so it seems to me that this is better? so why arent more people doing it..and this is the first that i have ever heard of it..have i been under a rock or what?
also i tried to google it and no luck..anyone have a web site that i could possably purchase one of those cams from? thanks


JACKO
 
Stock SBC firing order is 18436572. The 4/7 swap cam does basically what it's labeled as by swapping 4 and 7 to the order of 18736542. Since 5 and 7 are paired cylinders that fire in sequence, after cylinder 5 receives it's intake charge, theoretically it somewhat "starves" cylinder 7, which gets it's intake charge next. The new firing order corrects this condition. I didn't see this program, but a 30 horsepower increase is a pretty extreme increase for just swapping 4 and 7 in the firing order (typically it's about a 1% increase in power). I'd be willing to bet that there was a different lobe profile on that new cam.
 
if you rearrange the new firing order as if the cylinders were labeled like a small Ford, the firing order is the same i believe. so Ford got it right first =)
 
StangNut86 said:
if you rearrange the new firing order as if the cylinders were labeled like a small Ford, the firing order is the same i believe. so Ford got it right first =)
Click to expand...
Ford's firing order is 13726548, but they number each cylinder differently than the way Chevrolet does. Even if the cylinders were numbered like Chev's, it still wouldn't match the 4/7 cam swap in the SBC.

What I don't understand is 5 & 7 are no longer paired with the 4/7 swap, but now 4 & 2 are, so what is being gained/improved here?
 
StangNut86 said:
so Ford got it right first =)
Click to expand...

they nailed the distributor location on the head. :lol: you don't have to crawl up in the engine bay to play with timing. :laugh: its a PITA for us short guys. :icon_mrgr
 
MCM said:
Ford's firing order is 13726548, but they number each cylinder differently than the way Chevrolet does. Even if the cylinders were numbered like Chev's, it still wouldn't match the 4/7 cam swap in the SBC.

What I don't understand is 5 & 7 are no longer paired with the 4/7 swap, but now 4 & 2 are, so what is being gained/improved here?
Click to expand...
that the 302 or 351 firing order?
 
dave89iroc said:
that the 302 or 351 firing order?
Click to expand...

i dont know much about fords but i heard that the 351Windsor and the 351Cleveland have different fireing orders?

but after this post back on topic please cause im seriously thinking about this cam swap.


JACKO
 
you will pick up power, depending on how well your intake/heads flow, plus i've seen it done a few times and it seemed to also help the idle quality of the motor.
 
JACKO said:
i dont know much about fords but i heard that the 351Windsor and the 351Cleveland have different fireing orders?

but after this post back on topic please cause im seriously thinking about this cam swap.


JACKO
Click to expand...


I changed over to that firing order to help stop #7 from running lean. The rear cyclinders run the hotest and since 5 and 7 fire right after each other #7 runs even hotter. I also use a 4 corner water passage intake to help circulate water through the rear of the heads.
 
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