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VG30DE/TT Billet Valve Covers

For the last year or so, I have been passively working on developing a new intake manifold for Nissan Z32 300ZX. By "passively" I mean gathering information, studying dual inlet manifold designs that are already available on the market (not just for Z32) and making a few CAD sketches here and there to help me visualize things. For the most part, I already have a good general idea of how I want things to work, look and be manufactured. I've spent a lot of time with factory lower intake manifold when working on my billet fuel rail project, so that section of my design is pretty straightforward as of right now. Just like with my twin turbo system, I am looking to make everything symmetrical to help avoid variation in flow between intake ports. Manifold end tanks will require a good amount of work to complete because they are extremely important for proper engine breathing and there is no reason to create a manifold if it will not outperform factory counterpart. Even at the very first glance, an end tank that I want to design will interfere with factory valve covers since they have raised sections. I want as much freedom and space as possible for my end tanks because there are already numerous constraints that I cannot alter. Let's clean up these valve covers...

There isn't really much to a valve cover. It is designed to (imagine that) cover valvetrain and keep oil in while keeping dirt out. Most complex part of a valve cover is crank case ventilation port and baffles, but more on that later.


First and foremost, we need to create as much space under the hood as possible, which means that we need a low profile valve cover without any raised sections and pleasant in design overall. Simplicity is key here. Easiest part of this job was figuring out valve cover heights. We have to work around front cam caps that are 31mm tall and then add 5mm of material for part rigidity and sufficient material for cutting threads. No, 5mm alone is not enough for properly cut threads, but we can extend threads into the valve cover to an extent. Obviously we cannot extend too far downward to make sure we clear cam lobes. Again, more on that later.


Overall, we are looking at an 8mm flange (for rigidity), 5mm ceiling and 4mm walls. Very low profile and extremely strong construction. Once I built one valve cover and made up my mind about material thickness as well as radii of all fillets, it took very little time to build the other 3 valve covers. Unfortunately, on VG30DE/TT all 4 valve covers are different.



After a few more revisions, solid models were built and I was very satisfied with the result. A simple, low profile design, without any sharp edges. At this point, I needed to figure out a way to fill oil and ventilate crank case. I have made custom valve covers with weld-on bungs before and already knew that 12AN fill port would be ideal since it is not too big, but at the same time big enough to fit most funnels. I also knew that the placement of a fill port has to be right at the front of passenger intake valve cover (cylinder 1 runner overs the front of driver side cover). I had to play around with the exact placement for a bit since fill port cannot be too far forward because it can interfere with throttle body linkage, it cannot be too far back because it would interfere with cylinder 2 runner and it cannot be dead center of a valve cover because a cam lobe is rotating right underneath.

After a number of revisions and 3D printed samples, an exact fill port location has been confirmed. For a plug, I decided to go with a 12AN, low profile o-ringed version.


Deciding on location of vent ports was a lot easier. I did not want to vent from intake valve covers to avoid any interference with new manifold end tanks (which was the point of this project to begin with). It is not a good idea to vent valve covers from the front or the back since that is where oil can pool during hard acceleration or braking. Vent location was chosen around the middle of each exhaust valve cover and right above the largest drain area in cylinder head casting. Both vents are positioned towards the engine centerline because that makes them sit at the highest point on a valve cover. Vent ports were chosen to be 10AN o-ringed type (based on previous experience). When time comes and we move on to dry sump oil pumps, these ports will also be used to evacuate crank case from the top and further increase vacuum inside the engine.


Vent ports cannot really be left as a "hole" in the middle of a valve cover. In most cases, adequate baffles need to be attached to the inside to further reduce chances of oil making it out. There are a few general rules to producing a proper baffle:

  1. When looking into port, there should not be any direct line of sight into cylinder head.

  2. Baffle should be around 17-20mm away from entrance into fitting to create an area where gasses would expand into and slow down.

  3. Edges of a baffle should be 2-3mm away from surface of valve cover.

  4. A splash shield is strongly recommended to prevent cam lobes adjacent to vent port from throwing oil on valve cover ceiling.


And voila...



Baffle was CAD designed and laser cut from a 1.2mm sheet of 304 stainless steel. It was then precision bent into shape. The fitment is absolutely perfect. I was actually surprised myself how well it came out. Baffle is attached using four M4 bolts which are set in place with red Loctite and vibration resistant lock washers. They are not coming out...



Last, but certainly not least, I needed a way to seal these valve covers against cylinder heads. I never liked factory intake cover gaskets because of a vague process during bolt tightening and a lot of Z32 owners have cracked their valve covers as a result. The liquid gasket on exhaust covers certainly does the job if used correctly. The problem is that in most cases, that gasket is not applied correctly, dry chunks of it make it into crank case and eventually into oil pump. It is also messy and very hard to clean up properly. Most OEM valve covers are now sealed using Viton o-ring style gaskets and there is no reason why we should not do the same.


The problem is that valve cover flanges are not flat, but rather have halfmoons and using a circular o-ring is not really an option. Well, I never sought an easy way out, so a natural decision here was to make a custom Viton gasket.


I built a 3mm wide groove on valve cover's flange and carefully tailored it's path to make sure my new gasket would make direct and sufficient contact with cylinder head casting. If you look carefully at your cylinder head, you will see that the casting is irregular and making a gasket is not just a matter of drawing straight lines.

CAD files for all four Viton valve covers gaskets were finally made and sent off to a factory to be produced. Results were absolutely fantastic!

We used natural color Viton as a choice of material since it resists all automotive fluids and has working temperature north of 450*F. This is absolutely the best material for application and will form a reliable seal.


Final results left me very satisfied. This is exactly what I wanted to see in valve covers and I am fairly certain these will become a standard part in many Z32 builds.


Lets take some time to appreciate the final result. Last two pictures show valve covers installed on a driver side cylinder head and different hardware that will be available with these valve covers (stainless steel, Zinc plating and Zinc Yellow-Chromate plating).



I obviously did not stop there and produced a magnesium version of these valve covers as well. In essence, they are the same dimensionally, but are 40% lighter than the aluminum version. Magnesium valve covers have an "Mg" logo engraved into them. Obviously a magnesium set can be ordered without a logo.


To summarize, these valve covers will be available in 6061 billet aluminum in natural machined silver color, or anodized a color of your choice. They will also be available in billet magnesium (at extra cost since material is much more expensive). Please keep in mind that magnesium has to be anodized as well and looks pretty much the same as anodized aluminum version.



Product page for these billet valve covers will be up on the website shortly with full description, pricing and options to bundle these with Radium Engineering catch cans.


Thank you again for your support.

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