LT1 Camaro Timing Issues

[camaro95]

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

[PETE PEERY]

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

Hope this helps,
Pete Peery

[camaro95]

Thanks Pete but dowel pin on cam is good.

[Lee Valentine]

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

[Ed Wright]

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.

[Rich Biebel]

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.....

[PETE PEERY]

My son Kyle had pin break at No Problem raceway year or so ago and Jimmy Hidalgo was nice enough to help him. They drove what was left of old pin deeper in cam and installed new pin over it and was able to continue. When he returned home I removed cam and had it repaired and also built a larger headed bolt to replace one of the cam sproket bolts. This new bolt fit into the recess in rear of rotor drive so if pin ever broke again it would not cause a problem. Failure generally seems to occur when lift off throttle as this is when pops and dies. Whopping throttle as we do at finish line probably does not help matters either.