Hey guys,

So I've only had a running LT1 for 80 miles with this swap project that I've been in.

I got the motor back from the machine shop machined with cylinder walls 040 over, crank was line bored 20/20 because of two really bad spun bearings.

So round 2 started on Friday and yesterday we had the motor all assembled and installed in the car again. We went to start and it cranks and randomly backfires. No start. Timing light showed that the wires are getting pulses and since it's backfiring we're definitely getting fuel and spark.

My dad thinks the motor is 180 degrees off but that's impossible if the crank and cam gears were 12 o'clock and 6 o'clock respectively, right? We used the opti diagnosing thread to check the ignition module and coil and everything seems to be legit so it seems like it's the opti.

Now, my question is - if the opti was bad would it still be sending pulses at all and/or would I get any DTC error codes? I had DataMaster running while I tried starting the car and I didn't have any DTC error codes.

The only other thing we can think of is that the opti isn't indexed right. Is that even possible, though? It's a 1995 vented optispark. We took the original opti that came with the motor and then took the LT1 camshaft and tried putting it into the wrong slots and it wouldn't go into the wrong slots... only way I could see someone accidentally indexing it wrong would be to exert a lot of force on the opti to jam it in there. Mine slid in with no problems.. just wiggled it back and forth a bit and it popped right in.

My dad is going to drain the fluids and yank the radiator for me while I'm at work and then we're going to tear the waterpump out once I get home. Is there anything else I should have him check before he starts tearing the motor back down?

Also, when we reinstall the optispark or a new one, as long as the key slot lines up to where ever the cam dowel is it should be right, correct? Or do I need to bring the gears back to #6 TDC?

 

Start by checking the plug wires 1st B

Check the opti and the motor.

 

The opti can be put on wrong. Many people have proved that. You don't need to take out the radiator to work on the front of the engine. You will need to be at #1 or #6 TDC to get the opti to slide by the crank hub. Otherwise, the position does not matter.

 

If someone puts the opti in wrong, though, wouldn't they have to put a decent amount of force onto the opti to get it to go in? With the stock cam and the spare opti I had, we couldn't get the dowel to go into the wrong slots but we didn't push *too hard*

All I know is when I put the opti on it slid right into place.

Thanks for the help though - we'll try yanking the stuff out without removing the radiator. That'd atleast save some hassle of draining all the coolant out.

 

With the pin drive opti used on 95 plus model, you can get the pin in the right slot or any of three other not right slots. It doesn't take much extra force...you might not even notice the difference.

 

Yup - that's what it was. I was 120* off. Fixed the index put it all back together and got it to start for a few seconds. The car is flooded though so the only way I could get it to start was if I put the accelerator to WOT. I heard that turns the injectors off. But as soon as it starts then it goes way up in revs.

Can I yank the injector fuses to try starting it without putting fuel in and then pop the injector fuses back in or will that run it too lean and kill things?

 

It won't fire with out the injector fuse.

No fuse no fuel

 

I was thinking it'd atleast fire with what gas is still in the cylinders flooding it out? Guess not though. Hopefully letting it sit over night will get it clear and ready to run tomorrow.

 

man im glad you were able to get it fixed. i hate changing out opti's.

 

I'm just glad it was just indexed wrong and not something more serious. After installing it through the bottom, having it run for only 80 miles, spin two bearings, drop it back out the bottom, had it machined out and fixed, rebuild the whole engine, install it back into the car through the bottom again, I gladly yanked the water pump and fixed the opti than having to tear the whole motor down again.

This opti is in surprisingly great condition. I originally figured I'd have to yank the cover of the optispark off to see where opti was pointing then figure out what cylinder that corresponds to and compare that to where the crank was pointed. The opti was in such good condition I had to use a screw driver to pry the cover off. The inside was mint and absolutely no corrosion on the metal tab or posts.

Turns out having the cover off was perfect because I was able to hold onto the spinning assembly of the optispark while I pulled it off and that made it really easy to check which slot it was in and then put it back in ensuring it was indexed correctly.


That said - I just can't get over how easy it went into the wrong slot. When I compared the stock LT1 cam and the spare optispark that I have I tried forcing the dowel pin into the wrong slot and it wouldn't go on. Crazy!

 

So, how do you know which of the three slots is the correct slot?



That one with the arrow pointed to it is "slightly" different than the others right?

 

http://shbox.com/1/opti_back.jpg