Vicious95Z28

Just curious if any1 done it. What are the results?

Mindgame

All out race engines might see 1% if everything else is designed to compliment.

I'd look elsewhere for power.

-Mindgame

MY91Y84

its not all about the power increase...and its a lot more then 1%....if it was a miniscule 10hp on a 1000 hp motor there wouldnt be a need for a 4/7 swap cam...people have seen 15+ on a stockish motor from swapping out an aftermarket cam with a cam of the same specs with the 4 and 7 lobes changed...other then then power increase the motor will run smoother and produce fatter torque curve...go a step further and do a 2/3 4/7 cam swap...ever hear the 6.0 LQ9 truck motor run?....kinda sounds different right...thats because there firing order is in conjuction with the 2/3 4/7 swap...the torque curve is flat as a preteen and you cant even tell the motor is running....

LameRandomName

Results are mixed. I don't think anyone has yet figured out the right combination of variables to achieve consistant results.
If you're replacing the cam ANYWAY, such as during a rebuild, then try it.

GMRL

Is it just that motor that has the swap or do all Gen III engines have the swap also?

1racerdude

The 4/7 swap is the only one that makes power.The other swaps just sound good.
The computer issues aren't worth the trouble for the SMALL 1/2 % to 1% gain.
The big thing in a max effort engine is the main brg loading,the 4/7 swap equal's the load out on the mains.

Mindgame

In Reher Morrison's engine build book they list 8 possible firing orders for V8 engines. They go on to say that they have tried & extensively tested most of them. The 4/7 swap, according to RM was worth 5-8 hp on their PS engines (~.5%).

I can only tell what I've seen and I always narrow that down to the ones I've had some intimate knowledge of. Most of the guys I know who are trying 4/7 or even 4/7 2/3 swaps are only seeing a little less bearing wear & not much, if anything in the way of ET reduction. The engines "feel smoother down the track" but that's about it.

One other guy who does this stuff for a living says his BBC logs more uniform EGT's but he's still running within a tenth of where he was with the std. firing order.

I haven't heard of anyone losing power with the swap but I'm still having a tough time quantifying any gains from it. IMO, you're going to need a tri-y 4-2-1 header configuration to really try and take advantage of the swap & that's just another expense most street guys don't need.

I still say... spend your money elsewhere.

BTW- Can anyone link to dynographs of these 10-15hp improvements shown on "stock" engines. I'd like to see what else was changed.

I think you have to really read into this stuff before you buy it. Who knows what kind of gains might have come via a valvespring swap... etc..

-Mindgame

rskrause

Going along with what Mr. Mindgame posted, a lot of information is misleading even if correct. For example, the "gains" some people see after replacing plugs and wires might lead them to conclude that x-brand of wires and plugs are worth y-hp. In reality, all they may have proven is that a new set of plugs and wires is worth more than a worn out set. For gains as small as we are talking about, a very careful testing procedure is necessary wioth all of the other variables eliminated. How many people have done a 4-7 swap with NO other changes and adjusted test results for the conditions, etc.? I am not saying that the 4-7 swap isn't worthwhile, it may be. I just don't know. But I doubt 15-20hp on a stockish motor.

Rich

BMoney

the 4/7 swap and the 2/3 4/7, are mainly for engines turning more than like 7500+ rpm's. its has something to do with a more accurate spark at high rpm's to each cylinder.

1racerdude

Ya might want to go to Reher Morrisons site and do some reading on these swaps.

BMoney

oh ok thanks, but you might want to look up. Im not the one asking about it, I just gave my opinion on what Ive heard. I had a cam built from LSM and they made the 2/3 4/7 swap no questions asked. I had a small block turning 8800rpm's and that was the reason they said for it. so I apologize

1racerdude

Yea I know,but your assessment of what the swap does is incorrect.It has nothing to do with spark other than changing some plug wires.

Not a slam but more on the lines to get people to study up on these things before a nubee gets the wrong info and takes it as gospel and goes and spends a lot of money on something they don't need.
I ran this swap in the '70's in a dirt track sprint car and found no difference and can't find a reason it would work any better today.

SStrokerAce

Can't run the swap on a stock ECU. The fuel tuining would be off since it would only be getting the right signal from 3 of the cylinders on each bank.

Bret

Vicious95Z28

Totally understood.

HardcoreRM125

Yea, The injector timing would be impossible to change right?

As for spark, you could just switch the wires around ...

I have heard and read that it only eliminates harmonic vibrations.

Which in turn, is easier on the bearings.

Save yourself the time effort and money. Get a good balancer, and call it a day.

Besides the stock PCM wont allow the engine to rev high enough to benfit from it anyways.