Ok so i just had this thought, now i know that your basic small blocks firing order is 18436572 and that the ls based engine switched to the order of 18726543 because they could make the engine run more smoothly and get better economy/power/etc out of it that way. i also know they are more computer controled and use coil packs instead of a distributor on the manifold. so my question is can you use the ls1 computer on an older small block and change the firing order. would it benefit the engine in any way or just cause trouble, i know youd have to change the ecm out and maybe use the whole ls ignition system. but is it at all possible and would it have any gains or is it just a waste of tiime

 

you would have to have a cam custom made to open and close the valves along with the new firing order, and a custom crank shaft to match. So, basically, this will never work.

 

well i guess with money anything is possible. ok how about this, if your running a F.I. small block, can you use the ls1 pcm? ive read that they are more tunable and you can basically do whatever you want with them. note that theres are just idea from my head that i thought of clarifying im not actually going to do this unless i find something id like to do.

 

sure you can use it, along with coil packs and everything, with the proper setup, but that wont allow you to change the firing order of a SBC.

 

yeah i know, that was sort of a seperate wuestion with no relativity to the one above. what consists of the ls1 ignition system though, you have the pcm, coil packs, wires plugs, what else? i know it would have to be tuned for small block order/etc. do you buy a programmer to tune those or how do you go about doing that?

 

Nascar has been running the LS1 firing order for quite some time and the drivers say it has made no noticeable difference.

 

yeah but they have custmo grind cams and such which will run up a good deal of cash. i just read an article on here about coil per cylinder ls1 ecm, and stuff like that. ill probably kill myself trying to wire it together but id like to attemt it eventually anyways

 

And you "know" this .... how? And it accomplishes this, you think, just exactly ... how?

There's not much magic in it, if you just look at the orders.

Cylinders that are 4 positions apart in the order, are at TDC at the same time. #1 & #6, #8 & #5, #4 & #7, and #3 & #2 are at TDC in pairs.

Therefore all that this "new" firing order consists of, is exchanging which of the 2 cyls that happen to be at TDC at any given moment, is firing; and which is moving from the exh stroke to int stroke.

Big whoop.

Doesn't require changing the crank AT ALL, or anything else about the bottom end.

Doesn't even change materially which intake runners the fuel is getting drawn from. And, it just moves the cyls on the same side that discharge into the same exhaust sequentially, from being 8-4 and 5-7, to 2-6 and 3-1.

So far I'm not seeing any benefit.

"The whole ignition system" would involve the crank and cam position sensors.

http://www.eficonnection.com/eficonnection/24x.aspx

But since the firing order exchange accomplishes exactly nothing, you could use this reluctor wheel and just wire the coils in the other sequence, and still get the modern engine computer to work fairly easily, without having to uselessly and expensively change the mechanicals of the engine at all.

 

I did a 4/7 cam swap in my BBC this winter. I wanted a new camshaft anyway and the one I found was also a 4/7 swap. Changing my camshaft only required moving 2 plug wires around on the distributor cap. The plug wires coming off the cap look much better than before.

Any alternate firing order needs the appropriate camshaft. Any time one piston is at TDC on the compression stroke, there's another at TDC on the exhaust stroke. Simply changing when the plug fires doesn't change the mechanical timing event.

 

I was going to suggest the 4/7 swap. I know a few people who have done it and claim more horsepower and smoother idling. I cannot vouch for the "More horsepower" part (As they are not my car.) But just sitting in their cars I can tell a noticable difference in the way they Idle... As for needing a crank or cam trigger, you can use an accel trigger that replaces the dist with a gear driven trigger (part of their "Dual-sync" line IIRC.) The nice thing about using an LS ECM, (Besides the better tuning ability.) is that you can run "sequential-fire" for your injectors instead of the factory TPI "batch-fire".

 

the accel piece eliminates the distributor or changes the way it gives out its commands?

 

interesting subscribed

 

Sorry for the thread necromancing, but i have to comment on this...
the firing order swap, 4/7 and 2/3, DOES in fact accomplish a couple things. it lets the motor run smoother, and it reduces the harmonic stresses on the crank and main bearings. you may not get more power out of it, but you wont lose any either.

Also there is a heat problem that was caused in the older small blocks because of #7 cylinder tending to run lean, it ran hotter... with #5 and #7 firing back to back, the heat build up in that corner of the block could cause cooling issues. swapping 4/7 moves that heat build up closer to front of the cooling cycle and therefore reduces that issue as well.

all that would be required for this setup is a cam ground for it, (either the 4/7 or 4/7 and 2/3) then swap the spark plug wires on the distributor, and if its fuel injected (TPI/LT1) swapping the respective injector wires (would probably need to customize extensions for this).

saying that the firing order swap accomplishes nothing is not true at all. and for proof of the crank harmonics thing, look at the LS based vortec motors (5.3 and 6.0) that are running well into the 300k+ miles mark with no rebuilds... and some racers who do custom firing orders on their race motors are seeing crank life extended up to 3x what they would get normally.

 

When I got my custom cam for my 400 the cam guy asked me if I wanted the 4/7 swap. I did some googling and decide it was a marginal difference if any. I stuck with the old firing order. If you want to do it you just get a custom cam and swap a few spark leads around.

 

I read a tech article about the design of the LS1 and main reason for the change in firing order was to improve smoothness and reduce crankshaft stress. Another benefit of the smoothness is better crankshaft oiling. By all accounts of LS1 longevity, it seems to be working.