83 chevy blazer back firing

i put headers on my 83 chevy blazer 305, and when my brother in law took out the spark plug wires, he didnt label them. now the engine runs rough,and back fires, and also wont stay running. im wondering if resetting the engine to tdc and re doing the wires will fix this. thank you for any help

That would be a good 1st step. Just to be sure pop out #1 plug to make sure you are coming up on the comp stroke and put the mark on TDC. Take the cap off to see what electrode the rotor is pointing at to verify #1 and check the firing order in a clockwise manner.
1 8 4 3 6 5 7 2
thank you will be trying it today, will let you know how it goes
just took out the spark plugs and they have oil on them, thinking i blew the head gaskets?
Ok...Time to get a compression gauge and get a reading..... If the reading is high enough.... a cheap fix to get you going would be to install a non-fouler on the plug and of course may sure the firing order is correct.

Obviouly the correct way would be to repair the engine but this may get you by until you can afford to do it the right way.....
I think we might want to ask just where you found this oil. Was it on the outside (porcelain part) of the plug?

 

the oil was on the threads of the spark plug, i think it is the valve cover gaskets, they are both leaking
That's right. It's the valve cover gasket.

now i got he engine running fine, but it still back fires, would that have anything to do with have long tube headers with glass packs bolted to them? also, the engine hesitates around 25 to 30 mph, would that be due to needing a larger air filter?
How was it running before all this started?

If you didn't have the backfire problem before, you need to get back in there and triple check your work..... Take a good look at the firing order, especially #5 & #7, those are right next to each other mechanically & in the firing order.....Very easy to get installed incorrectly
the truck was running fine before, and the wires are hooked up right so i really dont know now. would not having any back pressure have anything to do with it?