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Derek

Twin cam head for the L6 from Derek at Datsunworks

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The last couple of times a twin cam 24V L6 head topic has been brought up I thought

to myself 'That Derek fellow might just be the guy on this forum to do this in a reproducible fashion'

 

If this comes in less expensive than a California divorce I'll be all over this...

 

I vote this for comment of the year! :lol:

 

Again, this is some fantastic engineering, great job Derek.

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The last couple of times a twin cam 24V L6 head topic has been brought up I thought

to myself 'That Derek fellow might just be the guy on this forum to do this in a reproducible fashion'

 

If this comes in less expensive than a California divorce I'll be all over this...

For the cost of mine, you could buy a damn fleet of used Ferraris. Hell, for the cost of mine, I could buy an OS Giken Engine complete, and the First Class Tickets to go talk to them in Japan several times while it's being built!

 

I pretty confident it will be less than that!

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Cheap as compared to the OS Giken:)

 

I think that comes in around $40,000.00.

 

Be careful comparing the TC24 (especially the latest version) to anything. What you actually get for your money is a key point, and often misunderstood.

 

Whilst I applaud your efforts, and I'm interested to see the results, I still feel a little non-plussed about it all. Like the 'Goerz-Paeco' (which never actually flew) and the OSG TC24-B1, your custom DOHC head is not going to be legal for any of the historic-based race classes and would likely be bumped up into a class where it will be outgunned. A slightly updated version of Nissan's FIA-homologated 'LY' crossflow or - far more practical - Nissan's FIA-homologated E4621 'Safari' head would be of interest all over the world (so perhaps a better business proposition?) and would be race legal in classes where they would count and would be competitive. Race legality / usefulness may not be an angle that you are concerned with, but if I had the resources it would be one of the first things I would think of from a commercial as well as practical point of view.

 

I noticed the tip o' the hat to the S20 with the valve cover, so you must have at least some empathy with the historic side of all this - yes? Casting '3000' into it might not be such a good idea though. How about giving this thing a name instead? Ultimately it would be more real than using the 'NISSAN' branding, in my opinion.

 

Lastly, I (fondly?!) remember HybridZ threads of the dim and distant past that scoffed at the usefulness of a 24valve DOHC crossflow layout in comparison to the stock L-gata's 12valve non-crossflow layout. Looks like the zeitgeist is a little different these days...?

 

Good luck!         

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The last couple of times a twin cam 24V L6 head topic has been brought up I thought

to myself 'That Derek fellow might just be the guy on this forum to do this in a reproducible fashion'

 

If this comes in less expensive than a California divorce I'll be all over this...

Love it.

 

I think I want my member name changed from "That Horny Z Guy"  to "That Derek Fellow" :)

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Hi 

 

 

Be careful comparing the TC24 (especially the latest version) to anything. What you actually get for your money is a key point, and often misunderstood.

I wasn't. I was merely using it as an example of the high end of things.

 

 

 

Whilst I applaud your efforts, and I'm interested to see the results, I still feel a little non-plussed about it all. Like the 'Goerz-Paeco' (which never actually flew) and the OSG TC24-B1, your custom DOHC head is not going to be legal for any of the historic-based race classes and would likely be bumped up into a class where it will be outgunned. A slightly updated version of Nissan's FIA-homologated 'LY' crossflow or - far more practical - Nissan's FIA-homologated E4621 'Safari' head would be of interest all over the world (so perhaps a better business proposition?) and would be race legal in classes where they would count and would be competitive. Race legality / usefulness may not be an angle that you are concerned with, but if I had the resources it would be one of the first things I would think of from a commercial as well as practical point of view.

Not the market I'm going after. This project is as much about proof of concept as anything else. Patternless casting has arrived. It seems expensive, but for this type of project it's ideal.  I'm not the only one doing this. Ford racing bought a few of the 3D sand printers and are using them in their head development. There is a guy reproducing Ferrari heads that are NLA, and I'm sure there are more.

I do a lot of motorsports work. This head will open up some of my clients eyes even further as to the possibilities.

 

I'm doing this head for the Z because it interests me. And I have a car to put it in!

 

 

 

I noticed the tip o' the hat to the S20 with the valve cover, so you must have at least some empathy with the historic side of all this - yes? Casting '3000' into it might not be such a good idea though. How about giving this thing a name instead? Ultimately it would be more real than using the 'NISSAN' branding, in my opinion.

 

I mentioned in the post that the nissan and 3000 were going to be machined in. The actual castings will be blank. 

Edited by Derek

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The idea here was to use something that has tremendous existing aftermarket support, or could be scrounged from a junkyard to complete a bare head and then upgraded later. Really the cams, rocker shafts, and drive were the big imponderables. One of the reasons for suggesting the K20 as Derek said was that we could flycut the head top and bottom on a mill, and simply bolt on the cam towers as is in the Honda. That means I could machine bare castings in the shed at my house (if I ever returned...) The rockers are available aftermarket to remove the odd lobe for the VTEC, and just run the aggressive profile which can be cut on a billet easily enough---remember they are ROLLER rockers, so a lot of that sliding friction goes away as does metallurgical issues. This head would really bring the L-Series into the modern day in terms of oil compatibility as well. 

 

 

 

You can also just use all exhaust rockers as they aren't Vtech.

 

As far as machining goes there is one point that may be vexing for people (me) who have never machined a raw head casting. Getting the tops of the valves to line up with the rockers.

 

I modeled in a cam tower and two rocker arms. The models are based on high res scans so they are accurate. I based the location of the tops of the valves from one of the heads I purchased. As you can see in this screen grab there isn't a lot of room for error as far as the angle of attack of the rocker to the valve top.

 

20170707041257-7b8fc3d2-me.jpg

 

This has been my biggest worry. I imagine you only get one chance to get the angles right on drilling the valve guide bores. 

 

I'm not totally sure if the head casting is any good or not. Castings shrink as they cool and you factor that into the design. The problem is at the level I work at it's guesswork. The more cores a casting has the harder it is to predict the shrink rate because the hard sand reduces the shrink.  So the reality is the casting may be too long or too short. It may also fail when I have it X-rayed.

 

If the casting is junk then I have 12 tries to determine the right angle. If the casting is good then I'll probably machine a plastic test head that matches the actual casting and practice on that.

 

If anyone has any experience on this kind of valve work I'd love to hear from you:)

Edited by Derek

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"Lastly, I (fondly?!) remember HybridZ threads of the dim and distant past that scoffed at the usefulness of a 24valve DOHC crossflow layout in comparison to the stock L-gata's 12valve non-crossflow layout. Looks like the zeitgeist is a little different these days...?"

 

Remember a key point of those discussions was the ultimate power compared to a $2,400 non-crossflow ported head.

 

$100,000? Forget it. Horsepower per dollar isn't anywhere close to comparable.

 

Nick a zero off that price and suddenly 330+CFM of port flow aat under 0.500" lift (which you will simply never get from a non-crossflow head) becomes relatively affordable.

 

There may be a class where it is race legal. That's being worked out as silently as the initial development was!

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Good luck with the machine work ahead of you. Hope the casting is sound.

We've been working now with 3D printing the tooling in metal (smaller stuff) for investment casting cores. Technology is moving fast.

 

Yea if I was doing this for a customer I would tell them to budget for four heads. One for the foundry to get right. One for the machinist and one for the unknown. If your lucky you might hit on #3.

 

There is a lot of good and bad in the 3D printing field. I just wish they hadn't settled on mesh as the modeling standard. I can be quite cavalier when I'm modeling for CAM. who cares about gaps as long as the smallest ball mill won't drop into it.  

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What features have you stripped out of the K20 in terms of Honda specialties? Have oil passages for things such as VTEC solenoid been completely removed? or are you simply blocking those off with a plate on the block?

 

Pretty much everything. Think of it as the ultimate Vtec killer. I still have things to work out with the cam towers and oil flow. Technically the cam gears would be in the back of the motor if all things were equal to the K20. Since I'm having custom cams made this won't be an issue.

 

Of course since it's custom anything is possible:)

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At least here in the USA, I don't know if even the LY head is legal with SCCA, VARA, HSR, SVRA, etc.  The rule sets are generally restricted to USA specific or FIA Group 3 except, maybe, for some IMSA categories.  There are a lot of so called "outlaw" series here like Redline Time Attack, etc. but I checked for the TC24B engine and it would be classed with essentially unlimited turbo cars.

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Pretty much everything. Think of it as the ultimate Vtec killer. I still have things to work out with the cam towers and oil flow. Technically the cam gears would be in the back of the motor if all things were equal to the K20. Since I'm having custom cams made this won't be an issue.

 

Of course since it's custom anything is possible:)

Alright, just wondering because looking at K-series design, most of the cam relies on VTEC for lubrication etc. of course I assume this wouldn't apply considering you're using two exhaust cams.

https://www.youtube.com/watch?v=OtRlQrAc5IY

 

What was your problem with the honda cam gears?

Edited by MaritimeRiceburn

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What was your problem with the honda cam gears?

 

The crank gear was too small to fit over the snout. single chain was my preferred route but there was just no way to make it happen. At least not with off the shelf components.

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Awesome job, if you don't mind, I'd like to hear more about the manufacturing end of things, I fully expected printing sand models would be possible, but I'd never heard of it actually being done!

 

I'll pm to keep the thread clean..

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Cometic will stamp out mls gaskets for you for all sides if you order 25 sets btw... might even be fairly economical considering they can just add ports to existing gasket designs for intake/exhaust if you're keeping any of them k-series style...

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The vavle angles are not really that difficult. Another thing to consider from using the Honda's engineering is this:

The valves are concentric to their pockets. All the pockets are already in-line. Indexing on a 5-axis CMM machine you find your origin off three valve pockets average locations using intake and exhaust.

 

From that point you can sink your valve guide holes. 

 

From that point you can ream your guides to size and from that you have a concentric point for valves and valve seats.

 

From that valve guide hole, since both rocker shaft and cam shaft is in the cam towers, the relative positions of their holes is set by calculation rather precisely.

 

The head bolts are independent of those points, thankfully so that you can get your entire camshaft and valvetrain setup using only the head as a reference. Obviously the cams and rockers, as well as the lines of valves should all be longitudinal parallel lines through a centerline drawn through the head, as would the head bolt holes.

 

Setting of the shuffle pins or reamed taper dowels for locking the cam towers in position is another machining step but once the relative positions of those three intake and three exhaust ports are determined--the relative position of the entire valve train can be determined. EVERYONE here I'm sure has seen valve seats in a head that looked 'off center' relative to the port--welcome to the world of 'casting core shift' --- the relative position really isn't that critical, and with the casting method Derek is now using the relative positioning of the ports, separation from centreline, etc should  be VERY precise compared to an older head made with traditional casting methods.

 

You just have to get the longitudinal axis for the line of valves determined using rough port diameters...you can adjust it quite a bit, relatively, inboard or outboard from centreline of the head to match the cam towers properly, and to make sure the valves are under the cam lobes (or more properly under the rocker arm tips) like they should be.

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Cometic will stamp out mls gaskets for you for all sides if you order 25 sets btw... might even be fairly economical considering they can just add ports to existing gasket designs for intake/exhaust if you're keeping any of them k-series style...

That may be what their advertising propaganda says, but their customer service in response to JUST such a request is met with cold shoulders and a resistance of the CSR to contact the engineering department to discuss ANYTHING other than what they already have in stock.

 

Yes, they will cut any gasket you want, but they are resistant far more than you're making it sound.

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RE: Derek's response to Alan T.

"Not the market I'm going after. This project is as much about proof of concept as anything else. Patternless casting has arrived. It seems expensive, but for this type of project it's ideal. "

 

What, tax deductible R&D with Advertising Possibilities? Like "BLAKE MACHINE 3.2 DOHC"?

 

Noooooooooooooo.

 

You mean trying to KEEP your money to do thing that are cool for your car  isn't a thought? C'mon people, there are MANY reasons to do this project if you are in the casting business, other than an altruistic self-sacrificing love of the marque model of Sir Lawrence. Consider this more like good old Mr. Raffles, what!

 

Man, I gotta go find some Sapphire and Tonic... the mosquitoes here are oppressive. What was it that the Dutch drank out of Batavia? Bloody hell, I'm not having any of that Civet-Crap Kopi!

Edited by Tony D

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EVERYONE here I'm sure has seen valve seats in a head that looked 'off center' relative to the port--welcome to the world of 'casting core shift' --- the relative position really isn't that critical, and with the casting method Derek is now using the relative positioning of the ports, separation from centreline, etc should  be VERY precise compared to an older head made with traditional casting methods.

 

Exactly. The combustion chambers, ports, water jacket and the front and back of the head are printed in one piece. If you look at the bottom picture of the casting you will see a tab on the front and a tab on ...well half a tab on the back. It short ran. Anyway on the front tab you see 2 pins. Those are hardened ground steel dowel pins that are cast in place. There should be 2 in the back, and that will be fixed on the next ones. Those pins will slide into a fixture on my rotary table. I'll then probe various points on the head to find the center of the casting. You then average out from there. I do this pin trick on all the larger castings I do. Makes life  little easier for the machinest. You know how cranky they can get.

 

When I modeled in the cam tower and rocker, the valves that I had modeled in previously didn't line up with the rocker. I tilted the valves .5 degree pivoting at the bottom of the valve guide and it lined up. 

So the difference between lining up and not lining up is half a degree.  Now I could drill from the top like the factory and wherever the valve seat ends up well thats where it ends up.  If I had a head to scrap this would be a simple fix as I will get the angle right after a couple tries. Trying to get it right on the first hole will be tricky.

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