4.2 blow by

[joshuapa]

What am I missing? Rebuilt 4.2 on my 87. Still lots of blow by out rear hole of valve cover. There’s a 90 degree elbow with hose. They have it run to bottom plate of Weber carb air cleaner. Behind the air filter. Everything I find anywhere with info. Says it’s normal, but it can’t be. And some only had issue when changed to Weber carb. Any help appreciated

 

[Gilaguy23]

Typically crank vents have the one hose into the air filter box to pull clean air. The Vac side is hooked up at the carb base or intake but needs a PCV or orface type system like the later 2.5 of 4.0 has otherwise if it was just a open 1/2 hose or something like that you'd have a massive amount of suction pulling on that line. As far as plain old blow goes I imagine you know what thats caused bythat being crank case pressure from shot rings,holed pistons to name a couple, stuff like that.