Clean Intake Valves
 

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?

Wow! Very impressive to see how clean they are after that amount of miles. Before I read your post having just looked at the pic, I thought they were new! I also use the best possible fuel that we can get here in Australia which is 98 RON, (BP Ultimate) and use Motul synthetic oil, changed every 5000Km (twice as often as Nissan recommends) along with a quality K&N oil filter. I also have an oil cooler and a large capacity sump. I hope my valves are in similar condition too. :driving:

That is very impressive indeed!! I thought the valves were new too.

As for me, I only use Chevron here in SoCal - 91 Octane. I always change my oil every 3 months/3,00 miles which ever comes first. I have used Nisan ester oil for every oil change and the Nissan oil filter.

Why I have used Shell Premium since day 1.

https://www.youtube.com/watch?v=4WPfLnVuQyM

After seeing your responses, I am thinking I may have stumbled onto something special. I had my oil analyzed by Dyson Analysis couple of times during the first year of my z's operation and Dyson recommended an oil based the outcomes of the analyses and my driving conditions. I drive aggressively, use quality gasoline and change the oil every 6000 miles.

Looking good!

Keep in mind, since our cars are "port injected" the valves get washed with gasoline when the engine is running and this almost stops carbon build up. However, direct injection does not and carbon does build up quickly on the back of the intake vales.

Why did you take off your intake?

I removed the intake to replace with a ported lower intake manifold.

Need to post a porting DIY. Anyone have any shots of how far off the casting is off and whether port matching is worth the effort?

I remember from the carburetor days that fuel and crankcase ventilation vapors passed through the intake tract and valves. Deposits on the intake valves was a problem then, but not so much now. The dispersant additives in fuels and oil formulations today control the buildup much bettter than in the past.

They look great.

I had a direct injected Mazdaspeed6 and at 84K miles I pulled the intake manifold to clean the valves and they were really bad. A combination of EGR carbon + PCV oil residue and no fuel washing because of DI is a bad combination. A lot of Mazdaspeed DI drivers will disconnect the EGR and run the PCV through a oil catch can to try to keep the valves clean. After cleaning part throttle drivability was much better but full boost power "felt" about the same.

Here you go:

http://www.the370z.com/intake-exhaus...ml#post3584432