LT1 Camaro Timing Issues
 

Hi, wondering if anyone has run into this problem - camaro lt1 efi stock eliminator with FAST Gray Box ECM, modified optispark which has just a cam sensor, msd crank trigger, Mallory Hyfire VII. Car was running fine and after a pass when letting off throttle engine backfired a couple times and quit, when trying to restart engine will pop and backfire a few times and attempt to run backwards when letting off the starter. Figured optispark rotor broke so removed and didnt see any problem, replaced cap and rotor with new AC Delco parts, no change. Fuel pressure good, Checked timing with light and is firing #1 cyl at approx 300 degrees on damper. Removed optispark distibutor and double checked rotor pointing (is pointing straight down on #1 TDC), verified tdc mark on damper, checked crank trigger is lined at up magnet when damper is at 50 degrees, crank reference is at 54 degrees (same as always) replaced mallory ignition and coil with known good msd setup, replaced crank trigger, still no change. This car has had this combination for many years without a problem until now. I'm hoping that I am chasing the right problem and that timing shouldnt be firing #1 at 300 degrees. I am just about ready to replace ecm setup because I dont know what else could be causing this. Again the car was running fine, put seven passes on it that day and on the eighth pass just after the finish line when decelerating is when this happened and car hasn't run since. Hoping someone else has an idea of what might be going on

Re: LT1 Camaro Timing Issues
 

More than likely sheared cam dowel pin, very common on these engines.

Hope this helps,
Pete Peery

Re: LT1 Camaro Timing Issues
 

Thanks Pete but dowel pin on cam is good.

Re: LT1 Camaro Timing Issues
 

If the rotor mount was not tig welded to the distributor shaft it probably spun and is out of phase. hope this helps. replace dist. with another and see if it runs

Re: LT1 Camaro Timing Issues
 

If you are using a crank trigger, the Opti has nothing to do with your ignition timing. Only injector timing. Usually when they do that on a pass, the blade on the rotor was hit and knocked to one side. You would have seen that when you had the cap off.
An MSD rotor won't do that. There is a fix to prevent a factory rotor from doing that.
So, you have even had the timing cover and c sprocket off?
Guess your crank trigger stuff was still tight?
Your dampener is keyed to the crank? The LT1s are not from the factory. They can slip on the crank. That would do it.
If you haven't already, I would check my cranking compression.

Re: LT1 Camaro Timing Issues
 

Line up your crank trigger wheel and timing pointer on number one cylinder.......pull the cap off and see where the rotor is pointing to in the cap.....if something happened to the distributer or cam you should see it there...Rotor should be pointing somewhere close to number one terminal in the cap. I would bet it is not....and something failed like Lee pointed to.....

Do you send the crank trigger signal into your ECU and then to your ignition box......or bypass the ECU and direct to the ignition box with locked timing....?

I ran my LT-1 with locked timing and did not use the ECU to change the timing.....

Re: LT1 Camaro Timing Issues
 

Thanks everyone for the info. Found rotor hub had slipped causing #2 cylinder to fire when #1 was suppose to. Not sure what caused it to slip, no damage to the rotor or cap was seen. Runs good now, hopefully no damage from the backfiring at high rpm

Re: LT1 Camaro Timing Issues
 

Cheaper and easier than having keyways cut, you can do like many have done to LT1s with blowers. Drill in from the front, between the crank & hub for a 1/4" roll pin. Drive that thing in there, it will be half in the crank snout & half in the hub.
If this is a Stocker or Super Stocker you should be running a SFI dampener anyway, which will already have a keyway. The crank should already have one. Put the key in and nothing will slip. I would recommend an ATI dampener.

Re: LT1 Camaro Timing Issues
 

Glad you found the problem!

Side note for you guys especially PETE- how many times have you seen LT1 cars break the dowel pin off?

Re: LT1 Camaro Timing Issues
 

None....

Never broke a thing in there...and don't think the present car owner ever had a failure there either......he has 2 LT-1 stockers

Gutted stock distributer....MSD cap and rotor....crank trigger...