Chevy LT and LS Ignition Systems

[2Loose]

It would be good to get some info posted here on the newer Chevy LT and LS ignition systems.

I salvaged the LT1 out of my wrecked 93 Camaro, along with the computer, and the T56 six speed, to rebuild and put into my 55 Chevy project car.

In the interest of time I had my LT1 rebored and rebuilt by Chad Golen with a stroker crank and lots of other hipo parts to 396 ci and 520 hp. This included Lloyd Elliott ported Trick Flow heads, 4 bolt main conversion added, specs are here if you are interested. I ported the LT intake plenum to match the heads and the upgraded throttle body, and added upgraded injectors. Rather than mess around trying to come up with a properly reprogrammed chip (the '93's were still a speed density system, with batch fire injectors, and used a plug in chip) I went to the F.A.S.T. XFI system.

My LT1 still has the front mounted "Optispark" ignition system. I have upgraded it to the newer vented system. The original system was non vented and open to the atmosphere, making it subject to moisture intrusion and corrosion. I'm also told that with all that high voltage energy bouncing around in there that ozone would build up and cause corrosion. Changing these units in the car is a royal pita as they are mounted behind the water pump. The newer vented units are vented to the intake manifold, which seems to keep them a little cleaner, keeps the ozone vented out, their service record is much, much better than the earlier ones anyway.

Many of these later Optispark systems have gone many thousands of miles without problems. So I am hoping this one will work ok for me.

Aloha,
Willy

Here's what my LT396 motor looks like, still not in the car (me bad !!!)

 

[2Loose]

I read somewhere that conversion kits are available to convert the LT style Optispark ignition systems to the newer LS style individual spark coil ignition system. I can't find it, so if anyone can point me in the right direction I would appreciate it.

At SEMA last year I saw several LS motors on display with the individual coils hidden away out of sight and the ignition wires routed under the headers to the plugs. A very clean looking setup.

The main problem with the original Optispark seems to be with the high voltage from the coil that goes through the optispark to the sparkplug wires, just like in the old fashioned distributor we are all used to. Apparently having all this high voltage jumping around in there is what eventually causes problems if moisture gets in. But unlike an intake manifold mounted distributor, it can't just be pulled or the cap removed to trouble shoot it.

This conversion system, from what I remember, changes the Optispark to only low voltage, and fires the individual coils, which then fire the spark plugs. It sounds like it would be a worthwhile conversion for my 55 Chevy project. Particularly if I can hide the coils and route the ignition wires "out of the way" for a clean looking setup.

Looking for comments, ideas....
Aloha,
Willy

 

[grumpyvette]

http://www.aa1car.com/library/dis.htm

optispark ignition info

The yellow circle shows the area where the coil and ignition control module are located. The coil is the part with the coil wire attached. The coil wire end looks like a spark plug wire end going to a distributor. http://www.rockauto.com/ (has good prices)...

garage.grumpysperformance.com

these threads (ABOVE) have bits of info that might be useful

OPTI testing

If you failed the injector pulse test we must make sure that all the power is getting to the opti.

With the test light and the car on KOEO, unplug the opti connector at the optispark and test for hot at the red wire at the opti. do you have hot?

If yes. Next step

if no, the pos feed comes from the computer. Check that the PCM is sending the signal, if not then you might have a faulty PCM



Next, using a multi meter on volts scale, test the red/black and purple/white wires for 5 volts. Do you have 5 Volts?
Yes, next step
No, The 5 volt reference is provided by the PCM, possible PCM failure or PCM power feed problem


Next, test the pink/black wire for ground. Do you have ground?
Yes, then the optical sensor is not working and is probably bad. based on the other tests run this is causing your no spark condition. It’s time to replace your opti. You can also check for corrosion or damage to the opti connector and replace as needed.

No, the ground is provided by the PCM, possible PCM failure or PCM power feed problem.

 

[2Loose]

I found what I was looking for. Bailey Engineering (LINK) has a device they call the "LTCC" to convert the Optispark from a high voltage spark distributor to a low voltage coil energizer. I don't know how well it works, but I would like to give it a try with the LT motor in my '55 belair.

Their web page explains it like this:
(Quote)
"Benefits of the system are: extended optispark life, much stronger ignition at high RPM/boost, built in adjustable rev limiter / two-step built in adjustable N2O / boost retard. It's just plain cool. It still uses the optical module in the Optispark, but no high voltage is passed through it, removing the source of damaging ozone that eventually leads to Optispark failure.

This is not totally a bolt-on deal, but will require some individual creativity on mounting the coils (making a bracket to hold the coils, etc) and getting the plug wires from the coils to the plugs, see the pictures below. The harness is plug and play, no splicing required. It uses 8 LS1 coil packs which you will have to provide along with some other parts. "

I'm sure I could find a way to hide the coils from view and run the ignition wires to the plugs from underneath. I'm not going to hang those ugly coils on my LT motor (see photo above)....

Aloha,
Willy

 

[grumpyvette]

ID bet a couple tall chrome valve covers mounted over the coils with slots or holes for the ignition wires to exit could be tweaked /fabricated into being a coil cover that just appeared to be extra tall valve covers
keep in mind,wet, loose, or broken electrical connectors or corrosion on connectors, is also possibly a cause of intermittent problems

 

[2Loose]

I'd say that's very possible. I already put tall ones on my LT just because I like the looks, and will adjust the master cylinder location as needed, if needed. Looking at a remote MC and booster mounted under the floor, like in both my trucks. But there's no reason I couldn't go back to the stock short covers and adapt a set of tall covers to go over the coils as you suggest.

Still, from what I saw at SEMA and discussed with a couple of tech reps there, no reason I couldn't mount the coils anywhere I want, within reason. I was thinking inside the front wheel wells on each side with a somewhat weather proof protective box over them, and route the spark wires back from there. I'll post what ever I come up with. It's a ways away at this point.

Other than the intake plenum and injectors, I am trying to keep this looking as clean and "old school" as possible. The guys I hang with all want me to convert it to carb and distributor, but I want to go this route....