I did plugs today on our '09 Ridgeline, and figured I'd take the front cylinder head cover off to check at least the front valves. All were well within spec, so I didn't touch 'em, and I actually didn't even pull the rear cylinder head cover. A few pics, with a caption following each picture.
This is the underside of the front cylinder head cover. Looks fairly clean to me. It's the color of 101k miles of conventional oil, but no deposits or coking on this.
This is the valvetrain itself. Pretty clean for 101k miles of either Pennzoil or Formula Shell at MM intervals (6-10k miles, usually). There is no trickery with the lighting, here -- the right side is significantly less discolored than the left side is. This is the J35Z5 engine, and it's got a different VTEC design compared with our MDX's J35A5.
In the A5 (MDX), each valve has an individual rocker arm, with a third intake rocker arm (for a total of three intake and two exhaust) used for the high lift lobes on the intake side. When VTEC engages at 4,400 rpm, that third intake rocker arm locks to the other two. With this design, the lost motion spring is down inside the cylinder head.
In the Z5 (Ridgeline), both intake valves share a wishbone-shaped rocker arm, and a second intake rocker arm rides the taller cam lobes. It's got a "foot" that points upward, and this rocks against the lost motion spring topside, in a girdle on top of the valvetrain, similar to a pushrod front suspension system. When VTEC engages (at 4,800 rpm in this engine), a pin locks the two intake rocker arms together, and the intake valves ride the higher lobe. Interesting twist on this design.
For comparison, the MDX's J35A5 valvetrain is below...and you can clearly see the lost motion spring under the third intake rocker arm.
And...the top and bottom of the J35Z5's magnesium intake manifold plenum, with the J35A5's aluminum one also, for comparison. The magnesium one feels like weighs about half of the aluminum one...
With the magnesium intake above, the intake manifold tuning flapper valve comes out with the plenum top cover. With the aluminum one below, the flapper valve lives in the plenum itself. Once assembled, both perform the same function.
This is the underside of the front cylinder head cover. Looks fairly clean to me. It's the color of 101k miles of conventional oil, but no deposits or coking on this.
This is the valvetrain itself. Pretty clean for 101k miles of either Pennzoil or Formula Shell at MM intervals (6-10k miles, usually). There is no trickery with the lighting, here -- the right side is significantly less discolored than the left side is. This is the J35Z5 engine, and it's got a different VTEC design compared with our MDX's J35A5.
In the A5 (MDX), each valve has an individual rocker arm, with a third intake rocker arm (for a total of three intake and two exhaust) used for the high lift lobes on the intake side. When VTEC engages at 4,400 rpm, that third intake rocker arm locks to the other two. With this design, the lost motion spring is down inside the cylinder head.
In the Z5 (Ridgeline), both intake valves share a wishbone-shaped rocker arm, and a second intake rocker arm rides the taller cam lobes. It's got a "foot" that points upward, and this rocks against the lost motion spring topside, in a girdle on top of the valvetrain, similar to a pushrod front suspension system. When VTEC engages (at 4,800 rpm in this engine), a pin locks the two intake rocker arms together, and the intake valves ride the higher lobe. Interesting twist on this design.
For comparison, the MDX's J35A5 valvetrain is below...and you can clearly see the lost motion spring under the third intake rocker arm.
And...the top and bottom of the J35Z5's magnesium intake manifold plenum, with the J35A5's aluminum one also, for comparison. The magnesium one feels like weighs about half of the aluminum one...
With the magnesium intake above, the intake manifold tuning flapper valve comes out with the plenum top cover. With the aluminum one below, the flapper valve lives in the plenum itself. Once assembled, both perform the same function.
