Stagger jetting question

[mbaird]

I am sure there are people that run staggered jetting but you would need O2 or plug readings off each cylinder to determine the exact jetting.

 

[92b]

Either way, I don't get the concept. Not saying it doesn't work, just say'n I don't understand how a cylinder knows to pull from one throttle plate where the jetting is XX and not the other throttle plate which is XX jetting.... when all 4 throttle plates are exposed on an open plenum to every cylinder.

We have o2s on each bank and egts for each cyl. on our dyno. This does not hold true 100% of the time but generally motors with poor fuel distribution can have wide splits from side to side on the o2s. Also wide variation on egt temps. Generally low temps represent cylinders with more fuel and high temps cylinders with less fuel. If you can move the fuel to even the distribution generally you will be rewarded with one or more of the following: smoother running engine, more HP , a more tuneable engine, lower bsfc numbers, less split side to side on O2s, more even exhaust temps.
Some techniques I have used and things that I have found that can affect Fuel distribution are: Twisting boosters, bending boosters, notching boosters, changing type of booster, staggered jetting, adding spacers, sliding spacers, removing spacers,changing carburetors, changing air cleaner base or top. Just to name a few. I have seen some of these tricks change a motor with an audible miss to a motor that doesn't skip a beat. It's good day at the dyno when that happens. Don't make the assumption that just because you have an open plenum to draw from that all cylinders are going to get the same amount of fuel. I say fuel but air would apply also. It's just that fuel is much fussier. It has more mass so it's harder to change directions and it is hard to get and then keep it atomized. As soon as air slows down somewhere fuel wants to drop out and puddle. It's hard to get it reatomized after that happens.

 

[92b]

I am sure there are people that run staggered jetting but you would need O2 or plug readings off each cylinder to determine the exact jetting.

Individual o2s for each cylinder would be awesome.

 

[Rat Bastid]

The 5/7 swap. My understanding is that it evens out the firing pulses that the crank sees. Since the crank is connected to the cam, the cam & valve train get a smoother ride which can add a small amount of power.

It’s a 4-7 swap.

 

[33IMP]

There is also a 3/2 swap. Much less common than the 4/7. The 3/2 swap ends up with the current LS firing order.
It doesn't matter what firing order swap you do, you still have a pair of neighboring cylinders firing in order next to each other.

 

[318willrun]

We have o2s on each bank and egts for each cyl. on our dyno. This does not hold true 100% of the time but generally motors with poor fuel distribution can have wide splits from side to side on the o2s. Also wide variation on egt temps. Generally low temps represent cylinders with more fuel and high temps cylinders with less fuel. If you can move the fuel to even the distribution generally you will be rewarded with one or more of the following: smoother running engine, more HP , a more tuneable engine, lower bsfc numbers, less split side to side on O2s, more even exhaust temps.
Some techniques I have used and things that I have found that can affect Fuel distribution are: Twisting boosters, bending boosters, notching boosters, changing type of booster, staggered jetting, adding spacers, sliding spacers, removing spacers,changing carburetors, changing air cleaner base or top. Just to name a few. I have seen some of these tricks change a motor with an audible miss to a motor that doesn't skip a beat. It's good day at the dyno when that happens. Don't make the assumption that just because you have an open plenum to draw from that all cylinders are going to get the same amount of fuel. I say fuel but air would apply also. It's just that fuel is much fussier. It has more mass so it's harder to change directions and it is hard to get then keep atomized. As soon as air slows down somewhere it wants drop out and puddle. It's hard to get it reatomized after that happens.

I like this explanation. Thank you

 

[furrystump]

I have seen the smallest wire ties on boosters with the ratchet on the outside. It creates low pressure and pulls more fuel/air towards that direction. If you have a lean cylinder you can “steer” the charge. Picture a string hanging down from the center of the carb. Which represents the charge, it will be biased towards the rich cylinders. If you can get it to start with a bias towards the lean ones. It might end up in the middle. Bandaids covering a compromise in the intake and firing order constraints. Thought I was going to have to really do some STEERING with my boondoggle of an intake, but the splits weren’t bad. I just wasn’t pulling enough air for it.