SSDude

I was watching a rerun of Horsepower TV today. They were building a stroker. The interesting thing is that they had a cam ground changing the firing order of the #4 and #7 cylinder. This change yielded a gain of 30hp (engine dyno). I was suppose to increase air flow.

N4cer

iTrader: (11)

Was it an LS-based motor? If not, that's why they did it. I believe that's the difference in the LS motors and the SBC motors' firing order.

SSDude

You are correct. It was not a LS1.

KRAZY K 2000 TA

iTrader: (5)

it was an old school SBC i watched it

Chalky

iTrader: (2)

I know this has been tried before and I thought it was a bit inconclusive. 30 HP seems to be substantial.

Asmodeus

well, I highly doubt the only thing they changed on the cam was the firing order. most gains were likely made elsewhere.

parbreak

iTrader: (17)

Well you probably didn't watch the show then. I watched it this morning and it was a staright up test on their new engine dyno and all that was changed was the cam. It was on a SBC. What incentive would they have to make up the numbers. I don't even think they mentioned a cam maker's name.

Asmodeus

oh, so it was the same lift? same lobes? same duration? same LSA? same everything other than changing the firing order? did they say it was?

parbreak

iTrader: (17)

They didn't say it was or wasn't, but the point of the test was to confirm or deny whether changing the firing order had an effect on horsepower. Their contention was it allowed a better mix of fuel and air. I couldn't give 2 squats about it one way or the other, but what would they be proving or disproving if they changed other parameters on the cam. The firing order effect would not be measurable. If you saying they snuck in a completely different cam profile to prove something they have no benefit in proving, then by all means "Conspiracy Theory" away!!

Asmodeus

well, who knows if they had the same profile ground or not, or if it was even available.. I'm not saying it was a conspiracy like "WMD" style conspiracy or "yellowcake uranium" conspiracy.. they had a show to do, a time to do it in, and MAY have left out a detail or 2 getting as close as they could to the original lobe specs. 30 whp the norm for changing the firing order on an old SBC? and this is just now being reported on/common knowledge? sorry if I am a bit skeptical.

parbreak

iTrader: (17)

I'm just messin' with ya on the Conspiracy stuff. No, it's not just being reported. They actually stated on the show, the idea has been around a while and I guess people were changing the firing order by other methods. Apparently the cam method is fairly new and they thought it would be a fairly easy test to do on their new dyno. The segment really wasn't even about the cam, it was about showcasing their new engine dyno room they had put in the shop and showing how having an engine dyno on premises will allow them to measure changes like this very quickly and easily without going to another shop. I think they were as surprised as anyone at the results.

Bryan

Asmodeus

ah, ok.. I wasn't trying to jump at anyone, just asking questions about it.. and being skeptical as I usually am. and no, I did not see this episode.

cws T/A

iTrader: (3)

the name was LAZER 240/ 246 @.050 didnt catch the lift. made 495hp regular 530hp swapped , 406 sbc, afr 23degree heads, single plane etc.

Asmodeus

I assumed it was a stock cam that got replaced.. not an aftermarket one.. interesting results then

Marc 85Z28

iTrader: (8)

The SBC 4/7 swap has been around decades. The off-the-shelf selection is extremely limited, available in only large solid roller grinds, and thus isn't very popular. Besides, real world testing (not HPTV ) has shown gains on only fairly stout SBCs. Your common mild 350 will not yield any additional power. And the LS1 has more than just a 4/7 firing order swap...

2000TransAmWS6

iTrader: (12)

i think the theory behind the 4/7 swap is to change when the air pulses in the intake occur to get better air movement through the intake manifold. it is something that they tried in Nascar many years ago and got outlawed.

stevewix

i had the 4 &7 swap on my last 555 shafiroff motor, and everyone i know running in the 565"+ range has a 4/7 swap. funny thing, it's a pretty common mistake to make (just once) but it would run 10.80's with the 4/7 swap cam and standard firing order, when the firing order issues was corrected it went 9.50's :lol

Cantalope Kid

iTrader: (2)

Uhhh...these Are Still Available In The Compcams Catalog Since Like Jesus Was Around...look For 4/7 Cams In The Online Catalog Under Chevy...and Stop Watching Tv! Your Gonna End Up With A Bunch Of Edelbrock Everything, Msd Everything, And Flowmaster Jizzunk! Do Some Research...don't Buy Just Because It Was On Monster Block Tv Specials...

Cantalope Kid

iTrader: (2)

Uhhh...these Are Still Available In The Compcams Catalog Since Like Jesus Was Around...look For 4/7 Cams In The Online Catalog Under Chevy...and Stop Watching Tv! Your Gonna End Up With A Bunch Of Edelbrock Everything, Msd Everything, And Flowmaster Jizzunk! Do Some Research...don't Buy Just Because It Was On Monster Block Tv Specials...

00454sscamaro

the cams ive seen with 4/7 are all advertised as high rpm cams when i was building up my 84, they might have more now. the ads i seen for them said 4,000- 8,000 rpm powerband.