Hello everyone I am having some problems with my truck it’s a 93 c1500 that I swapped with a LS1 and last Saturday night I was driving home I was at the light when I noticed it was smoking after I revved it shortly after that it backfired at idle and felt a misfire when I would hold it at a steady rpm. I drove it home and parked it I had to much stuff going on to check it out until today. I turned it on and no smoke came out during cold start a little after it got some heat in it it started backfiring at idle. So I pulled the plugs and replaced them. Cylinder number eight plug was black and it had oil after I replaced the plugs I started it and it ran normal I then went to drive it and it ran fine then I revved it to see if it would smoke and it would not smoke during the rev but 10-15 seconds after it will start smoking for a little bit. I was wondering if it could be the valve seal or the piston rings??? Hoping it’s not rings since im a broke college student and the truck is my daily driver. I will post the spark plugs from cylinders 1,5,7 and then you’ll see how bad number 8 is. Thanks for the help. Mods are BTR .660 springs, tick performance cam, longtube headers and a cold air

Cylinder #1

Cylinder #2

Cylinder #3

Cylinder #8

 

Can you run a compression test and maybe a cylinder leak down test? You may find the suspect cylinder has low compression?