Ok having issues with my vert.i bought the car with blown oil seals it would run but smoke alot to the point the muffler was dripping oil out back.pulled old motor out and put a fresh rebuilt street port motor in there now.

First start up of new motor was all good no smoke for about 10 minutes then it started smoking like a freight train,had to shut it off because it was too much.i let the car cool down and tried it again did the same as before was good for first ten minutes then the smoke began again.so I am thinking its the oil in the cats and exhaust that's burning off after they get warmed up and hot.

I got a hold of some good used pre cats and main cat but wondering if I should replace the catback as well.it has a custom made Y pipe and magnaflow mufflers that sounds good and really don't want to get rid of.car has all emissions stuff intact and I hope to pass smog after the break in of new motor.problem is since with old motor was dripping so much oil outback I think I have to change the mufflers out too because it might take too long to burn all that crap off I'm guessing.im going to switch out the pre cats and main cat and see if the smoke calms down a bit before deciding if I should switch the damn cat back.

Wish me luck hahaha

 

I'm thinking the smoke is from oil still being in the exhaust. And it didnt smoke immediately because the exhaust had to get hot to burn the oil off.

As you already said.

 

Just wondering if the mufflers out back are going to take a long time to burn off the oil or if I should just go ahead and switch them out.

 

It just needs to be driven. Was the engine JUST rebuilt? Probably the Vaseline and assembly lube burning out. Try giving it a water treatment after it's broken in a bit more. Inject HOT water through a vacuum line holding the revs at about 3500 RPM. Just dip the hose into a jug of hot water (microwaved) and let it drown a bit (a few ounces at a time) and as soon as it smooths out drown it again. It will steam heavily out of the exhaust, but don't be scared of it. The steam will expel build up in your exhaust and is harmless to your engine. It would actually steam clean your rotors too, but it was just rebuilt.

 

Yeah it was just rebuilt by me.when I build my engines they normally smoke for a few minutes on start up from the engine lube I use.but right now it's to the point where it's not drive able when warm cause of all the smoke.one of my neighbors actually thought my house was on fire.im going to switch out the pre cats and main cat and see how that goes.

 

Just let it burn away, no need to switch out the exhaust. It eventually will disappear unless its an engine problem.

 

So removed the pre cats and main cat and to my surprise pre cat #1 had fell apart and was clogging up pre cat #2 and the main cat was full of oil.installed the good set and turned on the car let it warm up and no more smoke.it was actually a good thing I removed them and replaced since one of them was clogged up.now my exhaust sounds better and revs up better too.

Pictures of the oil

 

Good thing u removed it,a clogged cat is bad for the engine. Too much back pressure

Rotary >Pistons

 

You don't need pre cats anyway.