1badroc_87

Hey guys, i was playing with the idea of doing a
4-7/3-2 firing order swap on my l98 and havent been able to find any out-of-the-box cam kits to do this. There are 4/7 swap kits, but i havent found one that does the 3/2 as well, as of yet anyways.

2 questions:

Does anyone have a source for a kit that would perform the full LS firing order swap, or would i need to re-grind a/my cam for this?

I’m assuming i would need to remap the ecu for my stock TPI, for fuel to be injected at the proper times. Or buy a new ECU. is this correct, and if so, which is more worthwhile?

thanks in advance

Fast355

iTrader: (2)

Why? Firing order swap only helps with a single plane intake and a carb.

Orr89RocZ

iTrader: (20)

Ls firing order would need new cam core. Only few sources for cores and they can be hard to find/get these days. To benefit from it you need full sequential efi

ls firing order is suppose to be smoother and easier on the main bearings. Not that conventional has any issue with a sbc anyway but there was a reason why gm did it

BOOT77

Sounds like a custom grind deal http://jonescams.com/

Isn't the stock TPI a batch fire for injectors like side to side?

BOOT77

Some would argue it also helps save the drivers side headgasket and improve larger stroke builds survival.

Plus I hear they sound better

Komet

Firing order swap on a sbc is a solution looking for a problem.

Fast355

iTrader: (2)

Funny, I went back to the traditional firing order on my 8.1L. I think the traditional firing order sounds better than the LS PUKE one myself. That is just me though. Also since I typically run Tri-Ys they are built for the old firing order.

Head gasket survival, that has to be trivial. The only place I have seen them blow is between 3&5 as well as 4&6 when they are overheated.

BOOT77

Well preference is one thing & Custom parts compatibility is well...

Far as headgaskets some would argue 5,7 is a hot spot, maybe more so with power adders....

1, 8, 4, 3, 6, 5, 7, 2

My point is there is more than one reason often to a mod and not everyone can benefit from them. I honestly wouldn't bother with a firing order swap sub 400 fylwheel hp But those who need that fraction of an advantage. Well that's what many of the mods that some say "do nothing" or "are a waste of time" where they shine.

Orr89RocZ

iTrader: (20)

https://www.enginelabs.com/engine-te...r-your-engine/

all you need to know really

The LS firing order is easier on the crank. It doesn't solve the problems of the 90deg crank, it just moves them around. You still have both cylinders on 3 of the 4 throws firing back to back, but with the LS firing order, it moves this to the rear 3 throws, away from the weaker front throw.

1badroc_87

these would be my reasonings for doing the mod, its an old motor and ive already had a HG blow. I do plan on pushing much higher numbers later down the line, but right now i’m building for longevity and reliability and all i’ve found on this mod in my research is that it eliminates hot spots and eases up on stress points.

Also; i personally enjoy the sound of LS motors, and think it would be pretty rad to have an 80’s sbc sound similar!

1badroc_87

it is batch fire to my knowledge, i’m just unsure as to whether it would inject for the 7-2 or the 4-3 at the right times. Also thank you for the link, i’ll check it out.

i was looking into comp as well because i know they do custom grinds, but i’m gonna have to wait a couple weeks due to trouble with my beater

1badroc_87

Bump because ive been doing some more thinking about this and something is bugging me.

would i need a new crankshaft as well? As it stands; by swapping the 4-3 and the 7-2, wouldnt that mean the 7-2 cylinders would be firing while the piston is bottomed out?

dont the outer pistons come up at the same time and alternate with the inner 2?

i’ll use an i4 setup as an example for my question:
would cyl. 1/4 be reaching tdc while 2/3 are bottomed out, or would 1/3 be at tdc while 2/4 reach the bottom?

Orr89RocZ

iTrader: (20)

Crank is fine. No change needed

DIGGLER

iTrader: (1)

No the crankshaft stays the same, you are simply swapping around the valve events of the cylinders and the ignition sequence. this is pretty much a waste of time, in my opinion on something running a very small duration/lift. you may not notice much of a sound difference even. this will be a custom billet cam, and will be expensive, since nobody typically is going to do a 4/7 swap on a low rpm small cube TPI setup. You would also need to figure out the distributor gear situation... would need to be compatible.
as mentioned above, gm did it to even out the stress on the crankshaft. engine masters proved there was no real power to be found with the swap.

F-BIRD'88

Re: firing order swap:
You must have a LOT of money to waste.❗️