Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Blow-by on a fresh motor

General Engine Building Discussion

Forum Posts



Tech Articles

Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.

= Resolved threads


Hey guys, I just finished my rebuild on my 1JZ. I'm pretty positive I assembled everything correctly as i'm usually very thorough in checking clearances and ring gaps. Anyway, I am getting an excessive amount of smoke/vapor from my vented oil catch can. It is bone dry and all that is coming through is the smoke. The rings on this motor have not yet been broken in, so i'm assuming this is normal until the rings properly seat themselves. What are your opinions/advice? Should I order a set of rings and refresh again before the car hits the dyno, or is this not a big deal?


That's a hard question to answer, not only are there several things it 'might' be, but the definition of 'excessive' is open to interpretation. Is it actually being blown out, or drifting lazily out, is it better or worse as rpm rises, what about a blip of the throttle, was it right from the start or has it changed during the engine running? Is the fuelling approximately correct? What is the breather setup - where is it venting the engine from?

Not an engine I'm familiar with, but those questions 'should' help others that are.

Did you do a leakdown test to determine there is compression leaking from the rings? Unless that was bad, I wouldn't take it apart to change the rings.

Is the catch can venting new, or what you've had in the past? If new, do you have a restriction from the valve cover breather? That can be a source of very hot oil that will show up as smoke.