4/7 swap
 

I read somewhere that the 4/7 swap was appropriate for the driver side forward block , but the pass side forward block needed a different firing order to yield a benifit. Thoughts and comments ?

Well for example the Chevy distributors do spin the other way from a Pontiac because of that bank swap deal, and that set up also sucks the distributor drive gear into the Cam gear and is why Chevys chew up gears like mad when loaded hard enough by the oil pump!

Mine has a 4/7 swap. Paul C spec a hyd roller for my motor, I gave him all the spec's on the motor and the car for him to work with. My son might want to chime in he talked to Paul more then I did or Paul C might want to.

I think the main benefit of the 4/7 swap is when running a single plane Intake because that stops consecutive firing cylinders 5 and 7 from robbing air and fuel from each other as they do.

4/7 Swap
 

Now you have 4 and 2 firing one after other. What's the difference in your theory of 5 and 7 firing one after other and robbing?

Limelight beat me, but same thought for me, how is it different robbing air and fuel between 5 & 7 and moving it to 2 & 4? Either way you have 2 cylinder firing sequentially together. Each way the sequential cylinders are on the corners on the intake. Just asking :)

The #4 is firing it is closer to the front of the crank than when the left bank in to the front? I have heard the gains with NA engines come from better harmonics with the 4&7 swap? I suppose that has an influence on the harmonics.

When I have asked about going with a 4 & 7 swap it was told to me that they see gains it to move heat around on boosted applications. But what they see in NA applications is hit and miss on any kind of gain, and not a brand specific statement. More or less told me if you don’t mind shelling out extra $$ for a 4&7 core it doesn’t hurt, but don’t expect it to put you in front of the feild.

With intakes that have runner openings in the plenum, like T2 and Victor. Not only are you relocating the yank, you're adding a two one yank.

Clay

Mine has the 4-7 swap and 3-2 swap. From my understanding is all about harmonics and stress in the crank. I didnt spec the can, it came with the top end I bought.

You can argue differences between engine makes but the Engine Masters dyno show did this test 4/7 cam swap, going from memory it didnt show much of a power advantage either way also I think the biggest measurable difference was fuel distribution (efficiency)

Worth a watch. Motor trend channel on cable on demand

.

bingo

And the 4-7 3-2 swap is the LS firing order. Last I checked for one of those sticks the core was $1000

Yes dad has a 4-7 swap cam in his engine, the reason was two fold but the biggest reason why was because the large lobes that Paul spec'd was only available in a 4-7 swap.

Thats what I understood and the main reason I chose the 4-7 / 3-2 swap for my build. I was not sold the theory of additional power by anyone... Just smoother running through the RPM range taking stress of the rotating assembly / block trying to hold it all together.

I was originally building a Cast iron block... have sense gone with an aftermarket block and the harmonics are really not as much as a concern as with the factory block. Already have the came now.

SPEED SAFE, NICK

We've talked to guys that run dyno's and have been told they have seen no significant HP gains with the 4-7 swap in back to back testing.

However going with the full LS firing order deal has shown some HP gains according to a couple of builders I've talked to. In fact when I was looking into the LS cam cores for my BBC, Mike at Zimmerman racing told me they are worth about ~10hp give or take a couple on an engine like mine. Each engine may vary a little but that was the general consensus. I just had to decide if $1000 was worth it.

One thing I remember from the engine masters show they stated no matter what you chose for a V8 firing order you will still have adjacent cylinders firing at some point, I didn't explore those options

Seems like you would want those 2 at the rear of a crankshaft as to not induce more force / twist / harmonics through the whole crank just a guess tho

.

I think the Ford 351 Windsor had that 4/7 and 3/2 firing order also, same as the LS. Ford just labeled the cylinders different and the firing order starts with the right front bank.. Same cylinder lay out as a Pontiac with the passenger side bank to the front. So having the the passenger side cylinders out front didn’t stop Ford from doing it.

CYL 1 robs 2s inhale already! 2 would be robbing 4, but not efficiently. CYL 1 has a direct pull making #2 Intake closing event is moot!

Yep it's close.

1-3-7-2-6-5-4-8 for the windsor, the 302 HO also has this fire order.

1-8-7-2-6-5-4-3 for the LS

Here's a chart I saved from somewhere:


http://forums.maxperformanceinc.com/...1&d=1626878183


:)

LS copied the Ford 351 firing order for a reason.

Tom V.

let's throw out the manifold issues and run Hilborn's. let's concentrate on the smoothness/harmonics/longevity angle. What 's best firing order for driver side forward/pass side forward, or is there no difference?