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Twin cam head for the L6 from Derek at Datsunworks


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Since this is a completely custom head, will you be manufacturing cams for this head? 


How aggressive are you planning on making these cams? Will you be offering an option for street and racing? 


I'll be supplying a cast steel core for an additional price. It will be up to the end user to make arrangements from there. I will also be providing the necessary data to have machined steel billet cams produced. But ultimately It's going to be up to the builder of the head to determine what they want.

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Got the head back from X-ray on Saturday. No big surprises.

Here is a shot of the front half




Here is a closeup of a known shrink porosity problem.




I knew it was there because you can see it from the top. I wanted to leave it to see what it looked like in the X-ray. You can see it leads all the way over to the valve guide bore and in fact you can see it in the bore. I'll do a weld repair on the top and call it a day as it's too small a defect to affect the valve guide.


Controlling solidification shrinkage is one of the tougher aspects of casting metal. We'll try something a little different on the next one. 


Every head will be x-rayed before they get sold. This way people can have confidence in the casting before they invest in machining.

Edited by Derek
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As someone who has seen many x-rays, including live scanning of wheels, I'm still impressed... for a first casting, that's still damned good :)


BTW the wheels get scanned with the flashing only trimmed to a minimum but the rollers on the outside, they leave the lug holes and bore filled with cones too, they do as little as possible before the x-ray step. I know it's probably obvious, but I'd make sure you have a clear system/workflow what you need to do first vs after.


If you do find problem areas, consider adding more expansion pockets to machine off after...

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Made a little progress Saturday.

Machined the front of the head. I knew this was going to be a PIA from the word go. I just don't have a proper angle milling head to really go at it.


I bought a used angle head on ebay a few years ago. It's designed for woodworking but it was cheap so I went for it. In the first shot I'm using the probe to indicate off of the cam bores.





Here I'm surfacing the front of the head. The finish came out a lot better that I expected considering the rigging I had to do to make it work. 






Faced the upper timing chain tensioner and the upper chain idler mount, spot drilled the timing cover and tensioner holes. I'm going to drill and tap those manually as I didn't have anyway to hold drills in that angle head. No biggie.





Got lucky on the pilot bore on the idler mount. You have to tap it on with a plastic hammer. 





The chain fits well. I knew I was going to make a spacer set for the bottom gear since it's a single not a double like the stock chain. The single chain tracks along the center of the guides now which is what I was looking for.





Got the pattern finished for the front timing chain cover. That's heading to the foundry today. Hopefully they will cast it this week.


Still have a lot to do but I feel like I have a little momentum.



Edited by Derek
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Single up top or on the bottom. Non of the KA sets that I saw have a double on the lower chain. I did see some that had a double up top and that set will work on my head as well.  


My theory is the roller rockers should reduce the forces enough so that a single row will work. The K20 only has a .125" pitch single row chain. It is also one single chain.  The KA chain is .375" pitch. Because of these differences my gut feeling is it will be fine.


When I build the head I'm going to buy a set of (probably) Brian Crower BC1040 springs. Even though my build would run on stock springs I'm hoping to replicate some of the stresses a higher HP build would have. This should give the valve train a pretty decent test. I realize there are more dynamics than just spring rate at play but it's the best I can do.



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Yea, the rollers wont help as much as you think.  The stock shim on bucket design like I use is offset, so it essentially acts somewhat a roller.  I made my own sprockets and lower chain.  If you have an interference motor, and run it to 8500+ like I do mine, I would ditch the single row in a heartbeat! 

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That's one of the reasons I went with the KA setup. When I pulled the K20 chain out of the box I was like "is this a joke". It's soo small. 


Time will tell If the single roller will work or not. There is no way I'm going to make a set of gears until I see this one stretch :)

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  • 3 weeks later...

Been working on a bunch of stuff so I guess it's a good time for an update.


Got the pattern done for the cam cores and it's sitting at the foundry waiting to be poured.

Got the pattern done for the front timing cover and got the casting back from the foundry.

Today I was able to finish up the machine work on the timing cover and head.

The timing cover is a bit of a kludge as I had printed the mold before I fully finalized the timing cover. It works but it will be better in future versions. I had to get it cast and on the head so the machine shop could surface it all together.


Here I've mounted the cover to the front of the head, machined the surface flush with the bottom and drilled the front holes for the lower cover.



The front lip is a little thin. I'll add material to the pattern to thicken it up. I really should have left more material around the entire head. That way I could have made a cleanup pass around the whole thing. I have enough material on the valve cover to create a lip to hide it so it will look good when it's buttoned up. This head will have a water outlet on the side of the timing cover but future heads will use a coolant manifold like the OSG head.




Very happy with the internal fit. I need to rig something for the front cover bolts. The holes are right on the step. I'll add bosses to the pattern so it won't be a problem later on.





So I didn't try to make it fit this well but the "as cast" fit between the factory cover and my cover couldn't have been better. Of course it's in a spot where no one will see it :)









Got the exhaust flange from the laser cutter. I machined an adapter block to go from a stock Nissan head to my flange. When bolted to the Nissan head it will position the flange exactlyish where it will be with the new head. This will allow the header to be fabricated on a car without being dependent on having the head.









Next up is the intake manifolds and valve cover. I'm doing three separate identical manifolds. It's a little more expensive to cast but a whole lot safer as you're dealing with smaller items. Machining is easier as well.


Will it ever end :)



Edited by Derek
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Awesome Derek, it's exciting to see this come together.




Manifold adapter looks like it'll be easy to work with. How's the water neck going? I see the big squareish hole in the head, but not exactly sure where the water neck will line up at.


Originally I was going to cast it as part of the front cover. The general consensus was exiting the water over each exhaust port like the OSG head was a superior way to go. The production models will be that way.  I'm going to machine a separate elbow for mine and incorporate it into the timing cover.  

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