Alright I'm lost again. New 383 build cranks, starts, and stalls immediately. '95 vette
Ok so heres the story. New 383 build went in great. The motor started up instantly. Idled it for a minute to make everything checked out and it was fine other than a few codes that popped up. (MAF connector got messed up but fixed this, Vehicle Speed Sensor showed a code but not sure this is fixed because the car hasnt moved yet. Also the analog gauge oil temp sensor was being weird and still is. This doesnt comm. w/ the PCM on the vettes at least though.
Did the motor break in a few days later. Started up fine, ran 10 min at 2000 rpms but the engine stalls. Not sure why. Engine started right up again though so I finished the next 10min of break in.
Fast forward to now, I checked all plugs to make sure none are fouled. If I had to guess some looked like they could be a hair lean. Changed the break in oil also. Found my opti vent hose got chewed up by the belt so I replaced it. Car wont run now. It cranks, starts, and stalls. Everday it does this in the same way also. 1st try=almost stays running, 2nd try fires like 3 cylinders, 3rd try it wont fire at all.
Things Ive checked:
Fuel pressure-correct at 43.5 psi. I did have a pressure leak in the tank but I fixed it (loose hose). It holds pressure after prime. Racetronix 255 system
ICM- checks out after a swap
IAC-Checks out after a swap
Iginition Coil-checks out after a swap.
Other parts on the car
Opti-MSD cap and rotor- always ran fine on my last motor and worked at least for a bit on the new
BBK 58mm Throttle body- This is new but voltage checks out at TPS.
ARH longtube headers
LE2 heads and cam
New Trickflow 36 # injectors
Car is tuned for this setup

 

Compression test? Leak down test? Are injectors pulsing? Do you have spark at the plugs?

How is the car tuned when it’s hardly been run?

36 lb injectors seem high?

Are there any current maf codes or power train codes?

Pull plugs after the three start attempts... are they soaked?

 

You can take this for what it's worth. I just built a 383 as well for my '96. It started up and ran fine and even drove pretty good without changing the tune. The MAF seemed to be able to compensate for the larger engine with no real issues. So while I'm not sure what your problem is, I would not worry about the tune just yet. Plus that would just throw one more variable into your troubleshooting mix.

 

Kind of sounds like when my truck tripped the factory passkey system... security light on?

 

Optispark

-though i did read where you say this same one worked fine on your old motor

 

Like others have said, start with trouble codes and other known issues. Then, I think you need to look at a scan and see what data stream doesn't make sense. The computer is reading something that is making it do the wrong thing. I had a similar issue one time, and in my instance, it ended up being a coolant temperature sensor. The pigtail was damaged and caused signal to the computer to indicate the car was never heating up. It ran progressively rougher until it would stall after the car heated up a few minutes. In that particular instance, I was able to see that the mechanical gauge and the digital output on the dash didn't match. If scan data doesn't make any sense, check the wiring harness connection to the computer (connected, not corroded...). That causes problems as well. That was a tough one to figure out. The car doesn't need to be running. You can start looking at things when the key is on and just start doing a sanity check on what things do and don't make sense. That should get you going in the right direction.

 

had a similar problem, replaced ICM, and both coil connectors one at a time. The black coil connector was the second I changed, no problems since...