Changed bottom end to 402...car won't start
 

Car did start the first time and ran fine for about 2 mins then i shut it off, added coolant and now it just cranks and I get a fuel smell....any ideas?

You provided very little info. I assume that you installed an LS2 stroker 402 short block. If so, did you use the conversion harness? What about the knock sensor. What about the grounds on the back side of the heads, etc.?

And differences in crank sensor teeth etc.?

Plus if you're running 16% more displacement, somebody
had better tell the computer. Otherwise you will be lean
everywhere, and lean doesn't make for good cold starting.

I would bet on fouled plugs...

Try pulling the battery cable for a while or clearing the LTFT's, most likely this is fuel related, change of displacement or change of injectors, without the computer knowing what was done. Most likely it started the first time due to the LTFT's being zero, and as it warmed up the factor 02's tried to correct and are now stored in the memory. Either way, the plugs are probably fouled as well at this point.

Also remember a larger motor needs more air to idle than a small motor. If the idle/start up tables, have not been increased (these are in relation to ECT, as the ECT increases, the computer commands less and less air), the car may not want to start warm. So a cold motor will have a lot more air going into it through the IAC/TB than a warm motor.

Ok disconnected the battery and she started back. Just having idling issues now, cam is 234 244 I think and 115 lsa. Car is an 07 Vette 6 sp it had the right crank teeth I'm pretty sure. at 1600 rpms it drives like stock but below that it runs rough and stalls. Anyone have a tune for NA 402 with 9.5:1 CR?

After I installed my 402, I was getting many DTC codes. Probably mainly due to a high duration cam. Your no start issue might come back. Check to see if you have any DTC codes.

What software do you use?