New engine assembled, won't start - backfires

[meissen]

I used LS7 lifters and I used 1/2 turn preload.

Disclaimer: The exhaust was really rattling for some reason - it went away as soon as the exhaust warmed up and has not rattled again even after letting the car cool off over night LOL go figure.
[ame="http://www.youtube.com/watch?v=Tg4UwF0Epew&feature=channel_page"]YouTube - LT1 012[/ame]
[ame="http://www.youtube.com/watch?v=C_CPswSsTiM&feature=channel_page"]YouTube - Cruise by in Red Alert[/ame]

Deceiving videos though - my LTerms are about 20 counts off. I'm really hoping it's just the fact that it's the stock tune and will be fixed when I take it to the local tuner. Only bad part is the guy who is doing my tune is an hour away... so he's going to review my data logs and as long as he deems it to be OK I'll drive it out to him... if he says it's not safe to drive on the stock tune then I'll have to get a car trailer from U-Haul and tow it to his shop.

On a positive note, the DataMaster logs seem to be really good aside from the fuel trims (lol... guess that's a really good contradiction). The knock sensor isn't registering knocks like it used to - the first try with the LT1 (when it had the two spun bearings) right from the first start up it would register knocks. And, another positive is that the spark retard stays at 0 to 0.1 - it's so dang smooth. If anyone has datamaster and wants to look for shits and giggles - http://www.meissenation.com/datamaster/


Oil pressure has been great - about 60 when it starts cold and then 30-40 psi when it idles. New oil pump and the white spring mod seems to have been worth it. RPMs are spot on for the tachometer at idle with what datamaster shows. Haven't verified how accurate the speedometer is. I'm using a 1997 z28 gauge cluster in my 1998+ dash with a 1995 LT1 in a 1994 Camaro. And I can't forget my 2000 Trans Am door panels or my 1998+ rear end. I swear I need to get a spreadsheet to keep track of what year vehicle each item in my car came from.