ok i bought this chevy last month, the motor in it backfired on the guy and broke upper intake and everything else plactic on the thing.the motor was a 305 and i just got a newely rebuilt chevy 1996 350 5.7. i dropped it in. hooked everything up. i used my lower intake from my last motor on it and the injectors from the 305 cause i was told they would work. well i got it all in and now it wont start. cranks well. i got good fuel pressure. it stumbles but wont start. timing looks fine. cant figure out what to do, i had a mechanic come look over it and it baffled him. it sometimes backfires a little to. any help would be great...

 

try the 350 injectors and go over all the electrical connections with a fine tooth comb

 

Check timing, the most common mistake people make when swapping a motor is getting the distributer location off one gear notch.

 

^^^true enough the backfire gives that 1 away, get the #1 cyl to TDC and check the initial timing

 

I agree, sounds like a timing issue.

 

i checked and doubble checked timing and was told it was definitely close enough to at least get started at it wasnt the problem

 

so at TDC, the dizzy pointer is pointing directly at #1 cyl? what does the spark look like? is it strong looking? or is it weak? how are the grounds? if the grounds are loose, or bad, or not there the engine wont run, also, how does the fuel injectors look while you are trying to fire it? is it a nice cone? or all scattered?

 

how do i check the fuel injectors? strong spark

 

ok so after trying to start it for a wile i pulled my # 1 plug out and it was dry which makes me believe its not getting fuel. i also pulled my # 4 plug which was coated in fuel. what would cause this... fuel injectors or the timing again

 

i tried it again and checked all my plugs. 2,4,6,8 plugs are all getting fuel. so are 5,7 on the left side. but my 1 and 3 are not