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Twin cam head for the L6 from Derek at Datsunworks


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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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I believe tony is talking about dished pistons negating squish vs flat tops.

 

Agreed. What I'm saying is project the outline of the combustion chamber onto the top of the piston and dish only that. The quench pads on the head are still interacting with the flat areas of the piston. 

 

I can't do the kind of hand work people like PMC and Rebello do so I look to technology and it's precision. So if I had a combustion chamber like the one on the OSG head I would be looking at ways to not have to hand grind each chamber. That one just popped into my head. 

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Here are my nice little Rebello/JE forged turbo stroker P90 88mm pistons. The quench pads line up perfectly. According to Dave, he didn't do anything after they came from JE. I guess that if you had the design, JE would work with you on it.

 

post-45034-0-46775300-1465580467_thumb.jpeg

 

To give credit where credit is due, when I showed this to Jeff P, he showed me the piston design that he came up with and gave to Rebello that lead to this after some revisions. We stand on the shoulders of giants :)

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That would be really close. When I put my motor in the first thing I did after it was bolted in was to put the hood on and clay between the hood and oil cap. There was less than an inch. Probably 13/16".  There may have been 20mm but I didn't measure it. An oil plug as opposed to a cap would pick up another .787"

 

I love America, where I'm expected to be able to work in imperial fractional, imperial decimal and metric. I'd like to shoot whoever stopped us converting to metric in the 70's.

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All right you asked for it.

 

Got the bottom side completely finished.

 

 

Surfaced, head bolt holes and dowels, water passages.

 

20170707041758-937e825f-me.jpg

 

 

 

Chamber roughing pass.

20170707041803-a037ae00-me.jpg

 

20170707041806-140ad501-me.jpg

 

Finish pass completed.

 

20170707041810-911e5a84-me.jpg

 

 

The chamber size is 45cc's. This should yield a 10.8:1 CR on the build without changing the pistons. 

 

Thanks

Derek

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Very nice. I also like seeing a mill with shavings/swarf everywhere like that. That's how my mill looks when I've just finished a job (i bet you even cleaned it up a bit for that photo right). Too many pictures out on the net of perfectly cleaned mills that you could eat off. Before i got a mill I didn't realize how much of my shed around the mill would be covered in crap. It's a messy operation guys!

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All right you asked for it.

 

Got the bottom side completely finished.

 

 

Surfaced, head bolt holes and dowels, water passages.

 

IMG_1196_zpsxqyplvjo.jpg

 

 

 

Chamber roughing pass.

IMG_1197_zpsa0jdwqcc.jpg

 

IMG_1198_zpsa5nyaua8.jpg

 

Finish pass completed.

 

IMG_1201_zps37aoqcem.jpg

 

 

The chamber size is 45cc's. This should yield a 10.8:1 CR on the build without changing the pistons.

 

Thanks

Derek

Yeah baby!!! 45cc?!?! V2 is looking mega so far! Obviously no boost on this one.

 

Rough time frame before this head gets installed? I understand the work required, just don't know how much of "real" work you have on your plate.

 

I just want to see GoPro footage from on the road ;)

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Not sure on the time frame. Crane is 7 weeks to get the semi finished cores done. I talked to Crower and they said they could put one of their grinds on it since at that point it's a normal cam core. That's another couple of weeks. Crane just doesn't have any stage 1 type grinds in their library. I'll have the head done with the initial machining next week and I'm hoping everything else is done by the time the cams are done. After that it's someone else's (the owner) time table but he's ready to keep it moving forward. It's not a simple swap. Converting to ITB's from carbs at the same time.

 

Yes this is a NA build. Rebello kit with a 81mm stroke. Getting the chamber to 45 is a big deal. using the Ozdat calculator A normal 83mm crank stroker with 240 rods and a KA piston with -2.6 dish will make 11.3 :1 static CR. That means if you are running that combo currently it becomes a head swap only. If you have that combo and are turbo I can just make the chamber larger. The price for my stroker just went way down:)  I can't afford a 9000 RPM monster so I'm going to build a fairly mild stroker. I have all the parts except the pistons and now I can buy off the shelf. 

 

derek

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You're going to find that chamber really detonation resistant and the compression ratios being discussed are more inline with a turbo application.

 

I think 11.5~12:1 will be a "normal" street build with this setup, and considerably more if you are going all-out N/A.

 

It's not uncommon for the Turbo Honda guys to be running 10:1 with a level of boost which would surprise you!

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You're going to find that chamber really detonation resistant and the compression ratios being discussed are more inline with a turbo application.

 

I think 11.5~12:1 will be a "normal" street build with this setup, and considerably more if you are going all-out N/A.

 

It's not uncommon for the Turbo Honda guys to be running 10:1 with a level of boost which would surprise you!

 

Word. I cut my teeth on a turbo B16 with nitrous for good measure. Ran high 10's in a del-sol on a good day (slicks, no street rubber). Was running stock pistons and head.

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If you have the money then you should buy custom pistons. But like every product even people who can afford it hit a price point where it's all stop. You cross that line and it's hard to get back on the other side of it.  It will be interesting to see what 10.8:1 CR will perform like on a NA build. He can run it for a while and if he want's more CR then he can go that direction and change out the pistons.

 

The B motors ran 10.2 - 10.8 CR.

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Wish mine looked this good:)

 

20170707041816-e0d7d57c-me.jpg

 

Thats a piece of 1.25" linear shaft that I'm using as a gauge rod. It's a little snug when I tighten the bolts but the top of the head is nowhere near flat so I'm not surprised.

 

20170707041819-7b83b21b-me.jpg

 

Yes the numbers will be smaller on the next set of caps:)

Edited by Derek
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I think gollum was meaning on a turbo with the squeeze... NA they were considerably higher. For a turbo the forged flat tops will be a godsend for bolting on and just boosting!

 

That payback will be huge with a  GT42R .... 

 

Yes, the "high 10's" was in reference to 1/4 mile times. Not sure we ever put it on the dyno. Best guess was it was making about 350-400hp without the nitrous. Quite a lot of HP for an OEM longblock, with a fairly decent compression ratio, and not even basic port work.

 

I'd imagine we were giving up a lot of power, if only just under the curve, in system optimization.

 

But landing in the 10's NA is a good safe spot. Not leaving piles of power on the table for pump gas, and leaves room to go either way down the road (force induction or higher compression pistons).

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