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Twin cam head for the L6 from Derek at Datsunworks


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Maybe I have missed it,  but what sort of flow numbers do you have on the EX and IN?

 

Im glad to see you went with 8620 cams, over the cast cams.  We had that discussion a few months ago, and you were not wanting to go that route, but you will be very happy you have.  Make sure they copper plate the entire cam, to keep the undercut areas from getting heat treated.  Generally they copper plate the entire cam, then pre grind all the bearing surfaces and lobes and that removes the copper.  Then when they heat treat and induce the carbon with natural gas in the furnace, it will surface harden the critical areas, without making the torsional strength of the cam too brittle.

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This is all Tony D’s fault:)   Hi everyone. Some of you know me from my  DIY EFI manifold project http://forums.hybridz.org/topic/63445-making-my-own-efi-intake-the-first-casting/ &#

Machine work finished!   I can relax a little:) Just got done with their first bath. Still need de-buring and edge finishing but the majority of the work is done.    

Yes, the exhaust port 'could' use some work, the as-cast cleaned intake is flowing within 10cfm of a 4 hour port job on an OS Giken head.   Those numbers outflow most max ported SOHC heads

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Maybe I have missed it,  but what sort of flow numbers do you have on the EX and IN?

 

Im glad to see you went with 8620 cams, over the cast cams.  We had that discussion a few months ago, and you were not wanting to go that route, but you will be very happy you have.  Make sure they copper plate the entire cam, to keep the undercut areas from getting heat treated.  Generally they copper plate the entire cam, then pre grind all the bearing surfaces and lobes and that removes the copper.  Then when they heat treat and induce the carbon with natural gas in the furnace, it will surface harden the critical areas, without making the torsional strength of the cam too brittle.

 

Hi Brian

I didn't have the head flow tested. At this point with this head it may not be the most valid data. Plus I'm having to start to budget so I didn't want to pay to have it done.

 

Thanks for the info on the cams. That seems to be considered the best way to have 8620 cores prepped. I was really surprised how well the lathe work went. I used a .25" round insert and was able to do all the roughing before I had to pull out the steady rest. The round insert let me run a zig zag pattern. I only use the lathe to do prototype and tool room work so I just did minimal cut depths ad let it whittle away!

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Thanks for the offer! My plan is to put the head on my .040 over flat top and run it for a while. I'm then going to do a tear down for inspection. I will probably get it flowed then.

 

That cam looks great!. Did you leave the gear area coper plated and then machined it after it was hardened and ground? Or is that the pre-grind we are looking at?

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Hey everyone.

I now have a blog about this head on my site. I'm going to continue to post here but the blog is a condensed version of what you see here. There is a FAQ on the left side bar that has a lot of data. If you are new to this build you may want to come up to speed there and then start following it here as there is a lot of great back and forth that isn't on the blog. I will keep them updated in tandom but only with my progress posts.

 

http://www.datsunworks.com/Blog/

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  • 2 weeks later...

Lobe work

 

Got the 4th axis back up in the mill and decided it was time to do the lobes. My plan is to rough it out on one plane then rotate 90 degrees and rough again. Repeat at 180 and 270 degrees. I’m hoping there is enough material removed at that point to go straight to the grinder.

 
First step key slot.
20170707040152-3e7fc5a8-me.jpg
 
 
 
After this is done I have a fixture that clamps on the front and keeps the cam indexed to the 4th axis.
 
I machined a V block in line with the centerline of the cam and added a clamp. This is way too long to machine without a center support.
20170707040155-d4c7f9bc-me.jpg
 
 
First cut!
 
20170707040159-6eaec2dd-me.jpg
 
This is after the first roughing pass. I’m using  .035 depth of cut which is leaving a bit of a step. I may make it a little less on the next cut. If I decide to do a finish pass that will all go away.
 
20170707040204-13a2f1cd-me.jpg
 
Here I’ve rotated it 90 degrees. I also rotate it in my CAM program so it’s looking at it from the new direction when I calculate the new code.  4th axis work can be tricky if everything isn’t setup properly.
 
20170707040210-f35a6a14-me.jpg
 
That's it till Monday.
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My steady rest from the lathe is too tall for my A axis and I wasn't comfortable doing continuous motion roughing with just a V block and friction clamp. I'll do it on the finish pass. If I continue to make cores I'll make a steady for the 4th axis and go to town. 

 

Derek

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Cam cores done!

 

IMG_0573_zpsstlcfgjo.jpg

 

Had a problem with my 3D model for the lobes. I didn't catch it until it messed up 2 lobes. It was right on the edge of not needing a weld but I figured better safe than sorry.

 

They are boxed up and heading to Isky today. 6 days to get there, 6 to 8 weeks to grind, 6 days back. Now I know how my customers feel:)

 

I've got plenty to do. The manifolds are on the way to me so I can get that all squared away. Then the valve cover. 

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As always Excellent work! I am interested to see what you do with the intake runner lengths. 

 

Thanks.

Xnke worked out the header design and came up with the intake length.  10.5" to the base of the valve including throttle body, velocity stack and manifold. Manifold is 2.125" long.

 

20170707041252-fa31e9ed-me.jpg

 

Just *wasted* the better part of the day at work catching up on this entire thread. WOW, really inspiring and cool stuff going on Derek. Very cool, can't wait to see the final outcome.

 

Thanks

Yea it can be a bit of a time vampire!

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It's an educational vampire though, I've been trying to get in local applied technology college machining classes and toying with the idea of going back to school for a degree in mechanical engineering. Everytime I read through stuff like this it pushes me a little closer

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Tellin' ya Derek, we gotta post our CV's so budding Engineers have a roadmap to obscure and arcane head construction! LOL

 

I gotta ask about the roughing if the lobes. It wasn't uncommon to give full round Nissan Billets to cam grinders to have cams ground. And the blanks from CWC are full round. Is the effort of roughing the lobes resulting in a radically decreased grinding cost or ???

 

Seems if you got the indexing slot cut...that's all you need for them to go further on with the lobes. I assume your journals and any thrust faces are already finished and will simply undergo micropolishing once returned, or will Ron completely finish that aspect as well?

Edited by Tony D
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Hi Tony

 

 

 

I gotta ask about the roughing if the lobes. It wasn't uncommon to give full round Nissan Billets to cam grinders to have cams ground. And the blanks from CWC are full round. Is the effort of roughing the lobes resulting in a radically decreased grinding cost or ???

 

I tried to get an estimate from Ron for doing the cams. He couldn't give me any kind of figure until he saw how much material he needed to remove during the roughing process. So I would say there is a high cost for roughing.  All of the machine surfaces are oversized. He will rough them after coper plating and then bring them to size after heat treating.

 

I'm hoping that they aren't too pricy or if they are he can give me some dimensions that are closer so he doesn't have to do so much grinding on the next ones. 

 

They don't do K20 grinds and grinders that do don't want to talk to me. So they have to come up with a profile as well. They are going to give me a price when they get the cores hopefully it will be workable. If they are going to charge me to develop a K20 profile on top of the grinding then that may bust the bank.

 

I'll be really happy when this cam shaft drama is behind me. It's kind of sucking the fun out it.

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