I know that sometimes you guys and gals out there read a story about an engine and realize there is either something mentioned that you DON’T understand, or that there must be more to it than they are telling you because they think you WON’T understand. And sometimes the thing they mention might sound logical, but that doesn’t mean you understand everything you might need to. Piston-to-valve clearance is one of those things, but we’re about to learn you some stuff!
Piston-to-valve clearance is just what it sounds like. It is the actual gap between the valves in an engine and the top of the piston. There is a different piston-to-valve clearance measurement for the intake valve in each cylinder and the exhaust valve in each cylinder. The more well machined and blueprinted an engine is the more precisely those measurements will match. But, those measurements change, depending on where the piston is in the bore and where the valve is in it’s motion and there are times when they get much closer to each other than at other times. And if they get really really really close, and you lose control of the valve due to valve float, the pistons and valves will touch. That’s no bueno.
It’s actually less bad in a stock engine than a really well-built one though, because stock parts flex and aren’t strong enough to break each other as badly in some instances. But that’s another story. So watch the video below and let Richard show how piston-to-valve clearance effects you. Because it does! If you just go trying to slam a giant cam in something, without knowing your particular combo, you could be in trouble.
Watch.
Video Description:
WHAT IS PISTON TO VALVE CLEARANCE? HOW BIG OF A CAM CAN I RUN? HOW MUCH LIFT CAN I RUN? WHAT IS THE DANGER ZONE FOR PISTONS AND VALVES? WHEN DOES THE INTAKE VALVE HIT? WHEN DOES THE EXHAUST VALVE HIT? WHY CAN’T I RUN A BIGGER CAM? DOES THE PISTON CHASE THE VALVE? DOES THE VALVE CHASE THE PISTON? DID RICHARD REALLY CUT UP AND ALUMINUM 5.3L BLOCK? CHECK OUT THIS VIDEO WHERE I SACRIFICED AND SECTIONED AN ALUMINUM 5.3L LS BLOCK AND 706 CYLINDER HEAD SO I COULD BETTER ILLUSTRATE WHAT PISTON-TO-VALVE CLEARANCE IS. I ALSO DEMONSTRATED THE CRITICAL DANGER ZONES FOR THE INTAKE AND EXHAUST VALVES AND SHOWED WHY LIFT ISN’T IMPORTANT.
