Clean Intake Valves

[jrb55gh]

Many times performance will be degraded by deposits in the intake tract. One of the most important areas to prevent deposits is the back side of the intake valves. Deposits in this area reduce air flow past the valve into the cylinder at both low and high valve lifts. Checking this area is difficult unless you have access to a borescope or are disassembling the top end anyway. I took the opportunity to look at the intake valves on my 370z during the installation of a DIY ported lower intake manifold.

Below is a picture of the intake valves in one of the heads of my 370z. The car has run trouble free for 48k miles and 3 years with frequent red line operation. The back sides of the intake valves are virtually spotless for all the cylinders. Also the throttle bodies show only a slight amount of carbon buildup at the backside throttle blade idle position. I have used only Top Tier rated gasoline (toptiergas.com) and very high quality API SN rated 0-30 oil.

I am a little surprised by how clean things were after 48k miles so I am curious about the results others have experienced. Are pristine intake valves in the 370z the norm or does anyone out there see variations that might be related to gasoline and/or oil quality?