Catalytic converter caught on fire
 

Hey guys. So I bought a 350z 03 6 speed with a hydro locked motor. Bought a motor with 49k and I swpped the motors. After install had a few codes. Have cleared them all but p0328 knock sensor. But there is no knock so could that be a bad sensor???

So last night I added some seafoam into vaccuum and some into the gas tank since its been sitting for 6-8 months. After letting the seafoam soak we started the car and let it idle for a little while. The car sounded better and idled fine. Then Out of nowhere oil pressured dropped and my friend was outside the car and luckily he saw the flames and grabbed a fire extinguisher and we got it out.

No our question is why lol

You probably clogged the cats with the seafoam and all the crud it let loose. And if you did it in the vacuum and tank simultaneously doubly so. Ive done some research and the consensus seems to be to use the seafoam very gradually. And disconnect the cats if its a car.

I think the key here is your mention that the oil pressure dropped suddenly. You said:
A sudden drop in oil pressure is very bad. It typically results in an excessive engine temperature. That temperature is quickly passed to a catalytic converter, and the result could be a fire.

--Spike

Seafoam 1,
Nissan 350Z 0.
Anybody else think it's the bomb? I've heard so many bad stories.
I hope you get your car repaired...

Well I'm doing everything myself. The car had coolant. I had just filled it up. I'm ordering some test pipes with bungholes for the o2 that will take care of the cats. But once I instal them I can keep diagnosing the car

In order to work, catalytic converters get very hot. Back in the 70's when catalytic converters were first installed on cars, there were several grass fires started under cars. I think heat shielding eventually solved that kind of problem.