First a little background information -
A four-stroke engine, like our Duramax, has intake valve(s) and exhaust valve(s). In our case, we have 2 intake valves and 2 exhaust valves for each cylinder. These valves are open roughly 200 degrees of crankshaft revolution. Since a four-stroke engine requires 2 full crankshaft revolutions to complete a power cycle (360° x 2 = 720°), the valves are open less than one-third of the time. When the valve is open, the lifter is riding on the camshaft lob and the pushrod and rocker arm is holding the valve open. But when setting the valve lash or clearance, we are concerned about what the valve is doing when it's closed, and the cam is on it's base circle with no lift. With solid lifter engines, you must have some "play" in the lifter/pushrod/rocker-arm assembly or the valve won't shut completely, and you will have low compression, poor performance, and you'll burn the valves. If you have too much "play", you will have poor performance, excessive noise and perhaps shorten the life of the valvetrain components. We call this play "lash" or "clearance". For our engine, the recommended number is 0.012", aka twelve thousandths. This allows for heat expansion and valve face/seat wear. Most engines will get tighter (less lash) over time in my experience. You can make a little more high RPM power by running towards the tight side.
Your Duramax engine is 32 valve V8 with 16 pushrods that rides on a solid lifter roller cam. Normally the valves will never require adjustment during it's service life. But for us hotrodders, you will need to do this if you:
Swap heads
Swap pushrods
Swap headgaskets
or anything else that might change the valve adjustment.
You should not have to do this if you just change to head studs, but you might as well check them when you are there.
I imagine GM has a great procedure for these, but I haven't bought the service manual. So this is the way I adjust valves on bikes, cars, trucks, boats, lawnmowers, or anything else I've tampered with.
You will need:
36mm 12-pt socket and breaker bar/ratchet
14mm wrench (I like using a long handle version)
A set of feeler gauges that includes a single 0.012" blade, or whatever value you are setting them to.
OK, I do engines at TDC (Top Dead Center) compression-stroke only. There are 2 TDC's for each cylinder, TDC Compression, and TDC Overlap. Both valves are closed on Compression, and both are open slightly on Overlap.
I'm going to do them by the firing order as well, to insure I do not skip a cylinder. My way takes a couple minutes longer, but IMO is less troublesome.
Our firing order is 12784563:
A four-stroke engine, like our Duramax, has intake valve(s) and exhaust valve(s). In our case, we have 2 intake valves and 2 exhaust valves for each cylinder. These valves are open roughly 200 degrees of crankshaft revolution. Since a four-stroke engine requires 2 full crankshaft revolutions to complete a power cycle (360° x 2 = 720°), the valves are open less than one-third of the time. When the valve is open, the lifter is riding on the camshaft lob and the pushrod and rocker arm is holding the valve open. But when setting the valve lash or clearance, we are concerned about what the valve is doing when it's closed, and the cam is on it's base circle with no lift. With solid lifter engines, you must have some "play" in the lifter/pushrod/rocker-arm assembly or the valve won't shut completely, and you will have low compression, poor performance, and you'll burn the valves. If you have too much "play", you will have poor performance, excessive noise and perhaps shorten the life of the valvetrain components. We call this play "lash" or "clearance". For our engine, the recommended number is 0.012", aka twelve thousandths. This allows for heat expansion and valve face/seat wear. Most engines will get tighter (less lash) over time in my experience. You can make a little more high RPM power by running towards the tight side.
Your Duramax engine is 32 valve V8 with 16 pushrods that rides on a solid lifter roller cam. Normally the valves will never require adjustment during it's service life. But for us hotrodders, you will need to do this if you:
Swap heads
Swap pushrods
Swap headgaskets
or anything else that might change the valve adjustment.
You should not have to do this if you just change to head studs, but you might as well check them when you are there.
I imagine GM has a great procedure for these, but I haven't bought the service manual. So this is the way I adjust valves on bikes, cars, trucks, boats, lawnmowers, or anything else I've tampered with.
You will need:
36mm 12-pt socket and breaker bar/ratchet
14mm wrench (I like using a long handle version)
A set of feeler gauges that includes a single 0.012" blade, or whatever value you are setting them to.
OK, I do engines at TDC (Top Dead Center) compression-stroke only. There are 2 TDC's for each cylinder, TDC Compression, and TDC Overlap. Both valves are closed on Compression, and both are open slightly on Overlap.
I'm going to do them by the firing order as well, to insure I do not skip a cylinder. My way takes a couple minutes longer, but IMO is less troublesome.
Our firing order is 12784563:
