Lifter pump up ?
Posted: Wed Mar 06, 2019 5:26 pm
When my V6 ecotec has an intake manifold explosion and runs rough for a while after it, has it pushed an inlet valve open and let the lifter overfill ?
Non EFI gas systems (IMPCO, GRA, etc) back fire on ecotecs mostly at start up or under heavy load at very low rpm. They run rough because the backfire goes as far back as the regulator and it takes a moment for the regulator to refill the Gann hose between the regulator and the mixer. In my experience GRA systems are especially prone to this due to the mechanical nature of the throttle and jet/needle setup.
If the valve is pushed open, as in the scenario you are asking about, the lifter isn't over filling as such but is hydraulic locking. There should always be a little bit of free play within a hydraulic lifer, this is why we don't need to set valve clearances like we do with mechanical lifters, and the valve being held open, albeit momentarily, can end up bending a pushrod. You probably wouldn't know that had happened unless you took them out and checked them.