I removed the valve cover and checked the valve lash adjustment this morning on our 2008 CR-V. This is the 2.4L K24Z1 engine, and with right at 59,000 miles currently. Oil history: Valvoline white bottle from the dealer at intervals specified by the maintenance minder (about 7-8k miles each), from new until when I bought it with about 45,000 miles. When I bought it, I put in Pennzoil Platinum 5W-20, then Mobil 1 0W-20 at 50,000 miles, and Mobil 1 0W-20 again at 55,000 miles. So the oil you see in it is 4,000 mile old M1.
The camshaft lobes look great. You can see where the rollers roll on the lobes, but there's no real visible "wear" in terms of scarring, grooving, etc. The timing chain and tensioner guides also look like they're still new.
You can see how the 2-lobe version of VTEC works in this picture. The #1 cylinder (far left) is apparently on its intake stroke. The primary lobe (the big one) operates the right-hand intake valve and the secondary lobe (the skinny one) operates the left-hand intake valve. You can see the primary lobe has depressed its intake valve, but the intake valve under the secondary lobe doesn't appear to be open at all. In truth, it's cracked open slightly, but not hardly enough to even tell. Under 2,200 rpm, the two intake rocker arms are not connected, and the two intake valves operate independently. In essence, it operates like a 12-valve engine (1 intake and 2 exhaust valves). Once 2,200 rpm is reached, a pin within the primary intake rocker arm slides over and engages the secondary rocker arm, and both rocker arms operate off the primary (larger) cam lobe.
This promotes good port velocity at lower engine speeds to maximize torque in those conditions, and still allows for good mid- and high-speed operation with both intake valves operating off the "big" cam. You can also see the camshaft phaser on the intake camshaft just inside the timing chain. On this version of the K-series engine, the cam phaser can advance or retard the camshaft through 25 degrees of rotation in either direction. Some of the performance-oriented K-series engines have 45 or 50 degree phasers, but the economy versions have 25 degree phasers.
There is no phaser on the exhaust cam, and there is no VTEC on the exhaust cam. The exhaust rocker arm is shaped like a Y, and a single roller rides against a single cam lobe (for each cylinder), and the rocker arm depresses both exhaust valves. I assume this was done to reduce friction (only one lobe per pair of valves).
Insides look good for the miles and past oil history. My plan is to continue with 5,000 mile OCIs, but with PYB instead of a synthetic offering.
Larger picture versions here: Picasa
The camshaft lobes look great. You can see where the rollers roll on the lobes, but there's no real visible "wear" in terms of scarring, grooving, etc. The timing chain and tensioner guides also look like they're still new.
You can see how the 2-lobe version of VTEC works in this picture. The #1 cylinder (far left) is apparently on its intake stroke. The primary lobe (the big one) operates the right-hand intake valve and the secondary lobe (the skinny one) operates the left-hand intake valve. You can see the primary lobe has depressed its intake valve, but the intake valve under the secondary lobe doesn't appear to be open at all. In truth, it's cracked open slightly, but not hardly enough to even tell. Under 2,200 rpm, the two intake rocker arms are not connected, and the two intake valves operate independently. In essence, it operates like a 12-valve engine (1 intake and 2 exhaust valves). Once 2,200 rpm is reached, a pin within the primary intake rocker arm slides over and engages the secondary rocker arm, and both rocker arms operate off the primary (larger) cam lobe.
This promotes good port velocity at lower engine speeds to maximize torque in those conditions, and still allows for good mid- and high-speed operation with both intake valves operating off the "big" cam. You can also see the camshaft phaser on the intake camshaft just inside the timing chain. On this version of the K-series engine, the cam phaser can advance or retard the camshaft through 25 degrees of rotation in either direction. Some of the performance-oriented K-series engines have 45 or 50 degree phasers, but the economy versions have 25 degree phasers.
There is no phaser on the exhaust cam, and there is no VTEC on the exhaust cam. The exhaust rocker arm is shaped like a Y, and a single roller rides against a single cam lobe (for each cylinder), and the rocker arm depresses both exhaust valves. I assume this was done to reduce friction (only one lobe per pair of valves).
Insides look good for the miles and past oil history. My plan is to continue with 5,000 mile OCIs, but with PYB instead of a synthetic offering.
Larger picture versions here: Picasa