Alright so heres the deal my buddy bought a 89 Camaro Rs 2.8L about a year ago, pulled the engine out, he changed the oil pan, put headers on it (dont ask me why) did the brakes, new starter, new wheel bearings and new suspension bushings.
anyways he could never get it to start after he pulled the engine, he sold me that car for $150, i swapped around a wire on the starter and got it to fire up, now heres the problem it intermittently backfires as its running (not very bad, just a pop), some times it will go like 10 minutes with no back fire some times its every few seconds (it does it worse when its warmed up).
Before my buddy pulled the engine it ran fine, anyways I checked the compression (its ok), changed the plugs/wires/cap&rotor, it helped a little bit, but it still backfires, it has a few vacuum leaks, and its running headers with a Y pipe and nothing else, what should I check/look for to solve this problem, a mechanic I know said it my be from not having enough back pressure
also is there anywhere I could go to get some pics of where the vacuum lines go, i have a diagram, but i kinda need a picture as some are missing and not connected right

I bought the car to fix it and make a quick buck, if I cant get it going, The Rs Body Kit Is going on my other camaro, also there is a few parts im going to steal off of it, then sell the body, I figured it may not be fixable when I bought it

 

I adjusted the timing to 10 Degrees like all data said, so the timing's not off, and I drained the gas tank and ran fresh gas through it, and also somthing else wierd is when you let it sit for like 30 minutes and go to start it, it sarts and rins for like 5 seconds, dies, starts and runs, dies, and the third time you go to start it it finally takes and runs, and there is no check engine light, and yes it works, and I scanned it for codes

 

Come on, No Ones Going To Help Me?

 

Sounds like the headers are your problem. If you have no problems with your wiring (no grounded or crossed wires), fuel pressure is where it is supposed to be, and your timing is set correctly (normally not responsible for exhaust backfires, but you never know), then I would check the cat. Those vacuum leaks will cause you to run lean and may be responsible for backfires and the engine stalling out. Try capping them off until you know where to connect them to and see if that helps. I have a repair manual with the diagram but you will find it faster that I can upload that pic here. I will if u need it though. Hope this helps.

 

Alright, So I figured Somthing out, the car will only stop backfiring if I disconnect the vaccum line on the back top part of the intake manifold and let it suck air, as soon as I connect the correct lines up, it backfires

 

you'll get allot more help posting in the V6 section, where the V6 cars are only allowed to play

 

What does that line connect to?