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Discussion Starter #1
I just finished a 5.3 swap in my brothers nova. It started right up. I bolted up the exhaust and trans lines. Now it will pop out of the carb with flames and not start. It has the MSD 6010 box. 750 carb 241 heads 619 623 lift cam. Everything is new except the coil packs. I am so confused. Any ideas what would cause this? Could it be the exhaust restricting it so much it won't start?

Any help would be greatly appreciated.
 

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timing...or i have actually seen people have the coil pack harness upside down ( so the front coil connector is actually plugged into the back one.) just something to check. whats your timing at on crankup? 3 bolt cam or one bolt cam?
 

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did you set it up with an ign pill or with the laptop-was the valve to piston clearance ck'ed, proper preload on the lifters (not hanging open)
sounds more like ign. firing at the wrong time, are the coil banks wired correct
 

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Discussion Starter #5
This is a junk yard motor and coil harness so it was never disconnected. The piston to valve clearance was checked and was .120. How would I check lifter preload on this motor it's my first ls motor and I went by the book on torque specs for the rockers.
The MSD box has no pill in it yet and never hooked a laptop to it.
Is there a way to tell if the coil harness is hooked up wrong?
 

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Put a chip in it or hook the laptop to it and adjust timing , I don't remember my 6010 having a base tune in it . I have my lq4 at 15 degrees at 0 rpm around 32-33 by 2000 . There's a thread on here about timing .
 

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Typically when guys report this it will turn out to be a few things. Here they are:

1. Poor ground for the MSD box. This is most often the case. And, before you say with certainty that you know your ground is perfect, everybody else who had this problem said that too. LOL
2. MSD power hooked up to the factory coil power source on a pre-HEI GM; which is a resister wire. Once the car starts, the voltage drops and the MSD goes goofy or quits. Make sure the resister wire has been eliminated.
3. Sensor or plug into sensor poor connection.
4. Plugs have started to foul. Often on new builds people have the idle set too rich. lean out the idle and replace the plugs with new plugs solves problem.
5. Something goofy in the coil harnesses. I have heard stories of guys finding 2 wires in the wrong pin of the plugs or even where guys plugged the coil harnesses in to the wrong banks.

Hope that helps.
 

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The harness is labeled 1,3,5,7 and 2,4,6,8 for the coils. You have then on correct? If you threw a cam in and didn't measure the pushrods, you could very well be holding valves open. A compression test could reveal it is a damaged junkyard motor as well.
 

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This is a junk yard motor and coil harness so it was never disconnected. The piston to valve clearance was checked and was .120. How would I check lifter preload on this motor it's my first ls motor and I went by the book on torque specs for the rockers.
The MSD box has no pill in it yet and never hooked a laptop to it.
Is there a way to tell if the coil harness is hooked up wrong?
How is the box supposed to work if you don't tell it what to do?
 

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Put a chip in it or hook the laptop to it and adjust timing , I don't remember my 6010 having a base tune in it . I have my lq4 at 15 degrees at 0 rpm around 32-33 by 2000 . There's a thread on here about timing .
this...none of the boxes i installed had a base map in it... need to write one.
 

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Discussion Starter #14
We are in the process of rewiring the car now. We found lots and lots of bad grounds and bare positives. As soon as we are done again I will post results.

The bottom end is a junk yard motor with 66000 miles. But has ls6 heads that were just redone.
 
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