95ttoplt1

iTrader: (3)

Does cam motion have these cores?

96capricemgr

iTrader: (1)

This has been discussed before.
The added HP is supposed to come from adjacent cylinders not fireing back to back which causes number 7 to be starved for air.
The tests I have seen have often shown significant losses in one part of the powerband even when there are decent gains in another.

Fueling is another hitch on the LT1 as either 4-7 become batch fire or you swap the injector plugs and now you have them firing at the right time but the computer controls fueling by bank and now you have an injector from the wrong bank firing and the results being read by the wrong O2.

The TV show statement I think was just meant to say "motorsports entertainment" be it TV or magazines usually grossly missrepresent facts to make advertizers happy and he believes that is the sort of place you got this info.

joelster

There is a local guy with an sbc running around with that swap on his car. For us (LT1)you'd simply need to call Comp Cams. They have plenty of 4/7 swap cam profiles. A few make peak power at around 6800 if you choose to keep the stock pcm. Have them grind one to an LT1 core. You'll have to swap opti wires obviously, and also, cut and splice the wires for the respective injectors. It will make more power, but it will be way up in the rpm range. But the best thing is this:

IT WILL SOUND INCREDIBLE!! I swear, 6000rpm sounds like 7500rpm. People will know you have something wicked done to your car. I'm not sure exactly why, the exhaust pulses must form different harmonics or whatever, but it will be noticeable to a trained ear.

LT14LIFE JT

iTrader: (1)

A freind of mine who was considering a new setup had been talking to his builder and he mentioned the 4/7 swap. He claimed noticeable gain in hp and even more in the tq department. The swap is broadly used in the truck sled-pulling series. He never mentioned the price of getting that cam, but now after reading about the costs, it may be out of the question. i'll have to dig alittel deeper and see what I can find out.

joelster

I found this old-*** video from our local guys from '05. There is a silver 3rd gen running this 4/7 cam. I'm not sure exactly what specs, but I know it's pretty big. The video is 28 minutes long, but I wrote down all the breaks which it appears at. there is a good sound clip of it idling, and a decent one of it revving, but trust me, it sounds WAY better in person. Anyways the entire video is pretty cool, gets you a little pumped for spring. The markers for the silver 3rd are below.


http://video.google.com/videoplay?do...3&q=badazz


8:08
9:04
11:42
11:59
17:35-17:48 (good clip of idling)
19:29
28:14

enjoy! BTW it's a solid 9 second car.

Toplessghost97

Seems like you broke it down to the nit and grit, I could see doing this on a carb race motor, but not to a street car. Besides all that you mentioned the number one thing is cost of the actual cam. Thanks

the_merv

iTrader: (88)

Someone mentioned it..

Gen I/II Firing Order: 1-8-4-3-6-5-7-2
Gen III/IV Firing Order: 1-8-7-2-6-5-4-3

bigdan1

to second 96caprice mgr on this subject ....

back in the 70's (carb era) it was known that no7 cyl on sbc was inherent for lean condition because of proximity of no5 cyl ...combining this fact with intake function being to carry the air/fuel mixture to the cylinders........the 4-7 firing order switch was a positive move ...

nowadays with the fuel injector being close to the cyl intake entry + the fact that the intake nows carries air only , the switch to the 4-7 firing order gives less positive aspect ....

definitely gives a ford alike exhaust sound .....

Dan

joelster

Geez. If it didn't work, the Cams wouldn't be available. It does work, period. It only makes more power way up the rpm range though, so it isn't really beneficial for everyone. It does alter the sound a lot. Go look at the video I posted.

96capricemgr

iTrader: (1)

By that argument, hypertech, Jet, Granatelli, ebay IAT resistor kits etc are all good.

I had not thought of the lean factor Dan mentioned and that port injection would lessen that and with cylinder balancing can eliminate it.

I am not saying it is worthless just worth less than people make it out to be.

Shawn @ VA Speed

iTrader: (3)

The 4/7 swap cam is only worth anything on a carbed motor,and then its only good for about 10-15hp at the flywheel,and that depends on the combo.Some it makes no difference.Port fuel injected engine gain nothing.Ive built and dynoed many engines with both with not much difference.If they made a difference i would have one in my own car-but i dont and it has every high dollar and trick piece possible.

joelster

I don't think anyone said it was a substantial gain.

1SlowFormula

I like the thoughts of limiting crank deflection on a stock crank this way you can put in a cam that spins a little higher without all the fear of spinning a main bearing...

thesoundandthefury

iTrader: (3)

I have heard a rumor that the 4-7 lobe swap is the reason for the difference in exhaust note characteristics between LT1's and LS1's.

Is there any truth behind this?

1SlowFormula

that is part of it, but the LS1 also has the 2/3 swapped...

thesoundandthefury

iTrader: (3)

I guess it would have helped if I hadn't stayed up all night and had enough attention span left over to read the whole thread.

Paul Bell

iTrader: (9)

The increase is small but it does lighten the main bearing loads. In addition to swapping the plug wires, you'd also have to swap the injector plugs.

The cam makers charge extra and make more money for their cam. That's where the big "gain" is.

The gains for a street or even a mild track motor don't justify the cost and work to make the change.

z_speedfreak

iTrader: (3)

dont forget about iron vs aluminum too.
interesting tho.. I'd love to hear one of these 4/7 swaped engines