LT1 Opti spark question
 

I have read that some LT1 racers are disabling the processor in the opti spark distributor so it basically is only a cap and rotor distributing spark to the plug wires. I believe this is called "batch fire" we have a crank trigger a BS3 and 7AL3 . So do I need the processor in the opti spark? How will the BS3 pulse the injectors without the signal from the opti spark?
Thanks

Re: LT1 Opti spark question
 

I am not very familar with the BS3 but I would think its just like the Fast XFI. The white wire marked points ties to the MSD points and your crank trigger should be hooked to the ECU with the correct harness. From there you have to program in the software for bank to bank. If you gut the distributor you no longer have a cam signal. We have a machined disc in the distributor and pick up a cam signal only off the opti for sequential tuning and use a crank
trigger. If you lose the opti signal it defaults to bank to bank. I did look online at BS3 instructions and saw that the gen4 can actually do individual cylinder tuning without cam signal but still fires bank to bank. Kind of a nice setup.

Re: LT1 Opti spark question
 

So your opti cam signal is only there for the XFI to pulse the injectors, and the opti no longer has anything to do with ignition timing?

Re: LT1 Opti spark question
 

Correct., Crank reference settings are important for this setup, on the opti dist rotor phasing is kind of set.
This is from BS3 site, I clipped the part out for what you were asking.

Type 3 - MSD Distributor Used to Only Distribute Spark from an MSD 6A/7A/8… box, with a
Crank Trigger.
Using a crank trigger and a CDI ignition module, like an MSD 6A, a distributor can be setup to just
distribute spark, when used in conjunction with a crank trigger.
Quick Setup Guide
• Find TDC, cylinder number one (1), compression stroke. See Find_TDC on page 20.
• Roll the engine back to 50o
BTDC.
• Install the crank trigger making sure the arrows on the crank trigger wheel are going on the
correct direction! See Crank_Trigger_Considerations on page 21.
• Line up the crank trigger sensor with the magnet in the wheel. Connect the red BigStuff3 wire
to green crank trigger wire. Connect other crank trigger wire to BigStuff3 black wire.
• Roll the engine back to the position BTDC (cylinder 1) equal to the max power timing.

7
• Install the distributor then “bump” the starter until it engages the oil pump drive while applying
a light downward pressure. Once the oil pump drive is engaged, rotate the engine back to the
timing mark on the dampener that will represent the maximum timing the engine will see at full
power. Turn the base of the distributor so that the distributor cap terminal for cylinder number
1 is aligned with the rotor in this position. Tighten the distributor down.
• Connect the BigStuff3 points wire (white) to the MSD ignition box points input.
• In the BigComm Software (Operating Configuration), set the crank reference setting to 50. See
Setting_The_Crank_Reference on page 25.
• Start the engine, with the engine still running verify that the BigStuff3 “Dash” timing advance
value equals the timing value seen (with a timing light) at the crank. Change the crank
reference value in the Crank Trigger window (in the Operating Configuration table), up or
down, until the “Dash” value and the crank value are the same. See Dash_Window on page 29.
• Dynamically check the rotor phase. See Dynamically_Checking_Rotor_Phasing on page 30.
• Lastly, you will want to verify cam synchronization. See Verifying_Synchronization on page

I have a gutted opti distributor with new MSD Cap and rotor that we used before in the parts for sale section if you are interested.
Hope this helps.

Re: LT1 Opti spark question
 

We never paid a lot of attention to these things as we bought the car race ready. It always ran pretty good until it didn't. Long story short we had a cracked cylinder wall. A new block some machine shop work our engine guy assembled the engine along with a new MSD opti spark. We cannot find (yet) any issues with the rebuild. But the car is lazy and extremely inconsistent. I could be wrong but it sure acts like timing issues

Re: LT1 Opti spark question
 

Do you have a timing pointer on the engine? On the MSD opti at least on the fast xfi crank reference angle is set at 1 degree. I always use the fixed timing setting in the software to verify that the ecu and actual timing on the damper are the same. Looking at the BS3 it seems to be the same procedure except maybe for optispark crank reference.

Re: LT1 Opti spark question
 

We will check. At this point we may just need to log some runs and try to figure out what is going on here. We have a T&T Sunday night at a local track,but it can be sketchy if you know what I mean.
Thanks for the help so far

Re: LT1 Opti spark question
 

LS1 Racer would you be willing to give me a call
Id like to ask you some question as i have an opti spark and Fast system My name is David 240-216-6455

Re: LT1 Opti spark question
 

PM sent

Re: LT1 Opti spark question
 

I use the MSD 83811 replacement for the GM Optispark. There is a metal wheel inside that has 360 small slots around the outside and 4 wider slots on the inside. You can use metal tape to block off all the holes except for the one that is to trigger as a cam sensor. The one hole that will be open is one of the 4 on the inside. I have to look at mine because I had a blank laser cut without any holes, but that one.

The harness is already there and it will plug into a Fast XFI system and I am sure the BigStuff would be the same. The purpose of the cam sensor for sequential is to see where the number 1 cylinder is in the firing order/stroke each time you shut off the engine. Otherwise, sequential tuning wouldn't work correctly.

On the subject of sequential tuning. How do you plan on measuring each cylinder for their respective O2 readings in order to make adjustments?

Re: LT1 Opti spark question
 

We unplugged the opti spark and are just using the crank trigger. The opti is just a cap and rotor function now.

Re: LT1 Opti spark question
 

Yes, it will be batch fire only which isn't bad. It will still run pretty well.

Re: LT1 Opti spark question
 

Tuners, and racers have debated the Batch fire verse Sequential fire for years. IMO, for all the expense and sometimes hassle to get the cam sync operational is just not worth it. Run batch fire and be done with it. Cam Sync's are mandatory for Coil on Plug applications, but if your car has a distributor/rotor w/MSD box I'd save your dough. For one thing, it's something else to mess up and cost you a round. Another thing is, for the novice, an ill operating cam sync system can be a bitch to diagnose.

Re: LT1 Opti spark question
 

You are right about it being a bit difficult and complex. We went through it and took all the steps we felt necessary to tune it properly. It definitely made a difference on our cars and we wouldn't go back to batch fire.

Of course, we also run Open Loop/Alpha A. That is another point of contention for some.

Re: LT1 Opti spark question
 

I have rebuilt several Opti's.
Stopped buying new ones if the Led Trigger is good.
Also a working Opti has the Rotor Clocked Correctly.

For Drag Racing, Remove everything.
If you have a good Trigger unscew it and save it.
Tape or Plug the Opening.

Save the Trigger Wheel if not bent.

Install the Rotor and Locktite the Screws.

Take the Long Electrical Connector that goes into left side of the Opti.
Cut the Wires and Install the Connector.
Plugs that hole.
Prevents water or moisture from gettng inside the Cap and Rotor.

There are two small tubes on the bottom.
Put a Rubber hose on Both.
Let them hang.