I have an 89 vin "E" Camaro that I've switched from TBI to a 750 cfm Edelbrock manual choke carburetor. After fixing many of the problems that i've had during this build, I got ready to get in the drivers seat, start it up, let the new cam break in and ride, but now i'm having the issue of a backfire in the carb as I crank the engine. My ignition system is a 6al msd cd box, blaster 2 coil, and an msd sbc pro billet distributor. In my experience this has been caused by a timing issue, but i've been messing with the timing all day and still cant get it to start. Everything seems to be in working order with the carb. Vacuum lines are completely new, and everything is hooked up. Not even a shot ether in the cylinders has worked, and i'm basically at the end of my wits with this thing and asking for help. Also knowing my luck it will probably be a very simple fix. Thanks to all for letting me share.

 

Also I just realized that is a really long post, but I tried getting all the info out there.

 

Are you using a fuel pressure regulator with a returnline?
Is it set at Edelbrock recommended pressure?
Pull a couple spark plugs & see if they are gas fouled

 

I switched to mechanical 41216 ac delco fuel pump, and I wasnt going to run a return at first, had this happen and now return is hooked up. Got new plugs after the first try just in case, 1 and 8 seemed to be just a tad bit covered in fuel, so I left all the plugs out for a little while, put the new ones in and same thing.

 

1. That is not a very long post at all.
2. Post as much as you can. We grow tired of the "my car won't start what's wrong with it?" posts that forget to mention the rebuild they just did or the fact that they have swapped something etc. We LOVE the information keep it coming it helps us help you

 

Thanks g92
When I tore it down, I had the block flux'd, no cracks, almost perfect condition. It had a few hot spots near the top at the combustion chamber, but the rings were perfect, hash marks were perfect, its like the motor was fresh from the machine shop. No need for honing or anything. Put it all back together with dart heads stainless valves big springs hot cam. torqued everything down to spec with lots of assembly lube. Tried turning the key with the in tank and regulator and the cd box hooked up to the ignition switch. Nothing, not even a drop of fuel, no wizz at the tank. The cd box didnt light up at all like its supposed to. The only thing it did was crank. Pulled the in tank out, put a sock at the end of a 3/8 line and put the sending unit back in. Took forever, but I found an adapter for a mechanical, which I wish I went with in the first place, hooked that up with a filter in front of and behind it. Hooked up toggles, which look awesomely fashionable by the way, to the starter and ignition from the very useful inverter up front. And now i'm here. Cranks like a dream with that red top I got up front, cd box lights up, before I put it back together I made sure I put the timing on mark to mark. I remembered compressiom stroke, compression stroke compression stroke, put the dist. In and poof! Thats all I get. Ive tweaked around with the timing, the carb, same result every time... Poof, and sometimes flame.

 

Verify valve lash is correct.
Verify TDC is correct.
Same with rotor phasing.
What cam and are the valve springs good with the lift?
Did you remove the tank pump?? If not did you remember to re-connect the wires?

 

I wish I could do this today, but I will have to wait until probably monday before I can touch it again since i'm out of town. For some reason, though your suggestion of checking valve lash just clicks. It does seem like the valves aren't seating all the way against the head. I would feel so embarassed if it runs afterward. When I get back home i'll back all the rockers off to zero and start again; I will post back my results after im finished. Thanks again.

Edit: I called comp cams personally so they could match a set for me, but I only assumed that they were correct. I know for a fact the cam has .533" intake lift, and .555" exhaust lift, but im out of town so I cant necessarily post all the specs right now.
I did take the in tank out and it is getting enough fuel to the throttle pump.

 

If the valve's are not seated properly against the head, that would give you the same side effects as timing being off. I think checking your valve lash would be a good bet.