My valve cover project is now officially a go; I just wrote the purchase order for the tooling and the patterns are now in process. I am hoping to have prototypes by the end of April, but that might be a bit of a stretch; we will see. Production parts should be available in June. See the link below in the vendor classifieds for information on getting on the list for these parts:
http://fepower.net/simplemachinesforum/index.php?topic=4737.0You would think that something as simple as a valve cover wouldn't be that difficult to design, but these pentroof covers have angles everywhere and I wanted to get a look at as many different variations of them as I could. I was able to look at the Cobra LeMans covers, the Blue Thunder covers, and a couple of different styles of Ford pentroof covers, including the ones with the Mercury script on the top (thanks to FERoadster for lending me those). I also needed to take into consideration the breather styles and locations, the ability to machine fins into the top side, the ability to cut the covers for clearance to the master cylinder or brake booster in some cars, having the ridges on the bottoms of the covers to hold the valve cover gasket in place, etc. etc. After screwing around with the design for a month or so I finally got a CAD model that I thought would be good; couple pictures of the model are below:
The nightmare of casting these parts is that you spend thousands of dollars on tooling, and then have fitment problems or some other issue that you can't resolve easily. This happened to me to a minor degree on my intake adapter castings. The first prototype I got had a thin spot in the casting by the water jacket as it went past a bolt hole. I had to have the water jacket core box modified to eliminate this issue, which cost me an extra $1800 that I wasn't planning to spend. I wanted to avoid this kind of hiccup with the valve covers.
Fortunately, I had recently got my 3D printer up and running, after buying it over a year ago (too much stuff to do!). The perfect solution was to 3D print a copy of the valve cover, up to a height of 2" or so, and test fit it on an engine to make sure it all looked OK. Here's a couple pictures of my 3D printer printing one of the valve cover models:
(Note: this print is of the full valve cover. All the plastic you see in the middle of the print is support for the roof of the cover, since you can't 3D print over air. This stuff tears away from the final print when it is finished).
The first print was extremely helpful, because I had a typo in one of the dimensions of the model that located one of the bolt holes, and it was off 0.100" from where it should have been. So, I modified the CAD model and printed another partial valve cover. I thought I was in pretty good shape at this point, because the bottom of the cover conformed in shape to the Ford valve covers I had on hand. However, my friend Kevin R pointed out that for people running the Dove end stands, most of the valve covers out there didn't fit. He offered to bring over his Dove rocker setup for a test fit. We bolted it on my test engine, and sure enough, the covers were not wide enough at the bottom to accomodate the Dove end stands (these are the ones that bolt to the head bolts). The end stands actually hang over the valve cover rail just a bit. I wanted my covers to fit as many different combinations as possible, so I went back to the CAD model and opened up the inside just enough to give 0.050" clearance with the Dove end stands. There was still plenty of area on the valve cover rail to seal to the covers, so I didn't have any qualms about the design change.
Back to the 3D printer one more time. This time the cover fit perfectly, even with the Dove end stands. I sent the valve cover model off to the pattern maker and the foundry for quotes.
I decided to print one more cover, a complete one this time, just to see what the whole thing looked like. Unfortunately, I ran out of white plastic for the printer about 3/4 of the way through the print, and had to finish it with gray plastic. Here's some pictures showing that print, and also the other partial cover print:
The partial valve cover print also generated an idea for a certain version of the valve covers. It wouldn't be too tough to machine the top off the valve covers so that they looked like the partial print, and then put a clear plastic cover on the top, for visibility to the valvetrain. What do you guys think of that idea?
One other item I would like some feedback on is the breather holes. For the valve cover versions with breather, I would like to go with a screw-in version. Blue Thunder has a really nice setup, but they use what appears to be a custom screw-in cap, with 1-1/2" - 12 fine thread. I can't find a ready made cap with this thread anywhere. What is available mostly is the 1-1/4" screw-in versions. Just looking at them side by side, it would be a lot easier to pour oil into the larger hole if you didn't have a funnel handy, but the smaller hole versions are cheap and readily available. I'm leaning towards those. What do you guys think?
Thanks for any feedback, and for your interest in this project - Jay
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