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Twin cam head for the L6 from Derek at Datsunworks


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Mmm, sausage...

 

Any particular reason for capturing the chain on both sides?  Kinda curious what a materials analysis would yield if you sent some chain guide material out for inspection. I remember having to get material composition certs for the ISO shop I worked at making aviation parts.

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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.    

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I'm not sure if I love that tensioner or hate it. I once had a plastic tensioner on my Toyota truck break down towards the bottom and the piece went into the chain, around the gear and snapped it, stranding me. This happened as I got in the truck to drive home from my wedding reception. Luckily a friend is a friggin ace mechanic and had wife and I on our way home in a couple hours. Bad timing though, in more ways than one. Anyway, I'm just a bit concerned that the chain might snap a little piece of plastic off of the top or bottom. Never seen a chain restrained on both sides like that, although I haven't been into that many timing chains, so maybe it's OK and I just haven't seen it before...

Edited by JMortensen
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Mmm, sausage...

 

Any particular reason for capturing the chain on both sides?  Kinda curious what a materials analysis would yield if you sent some chain guide material out for inspection. I remember having to get material composition certs for the ISO shop I worked at making aviation parts.

 

Because there is no kill like over kill in my book:)  It started out because I was concerned with the tension and slack sides of the chains being so close together. My first thought was to add a divider there like you see on the top of a KA24 upper chain. I was afraid any chain whip during an overrun condition would rip it off. Then It morphed into it would be easier to do an entire channel.

 

The orange brown colored OEM guides are made from nylon 4.6 which might as well be called unobtainum as far as I'm concerned. I couldn't find a source anywhere that wasn't "contact for a quote".  That usually means you can't afford it:)   The nylon 66 was recommended as a good second choice on an automotive engineering forum. Even still a .75" 1 foot square was like $80.00.

 

The steel plate is drilled to hold a Nissan 13085-7Y000 guide so that can be used in it's place. It doesn't offer the same amount of guiding since it isn't custom but it will fit.

 

I'm not sure if I love that tensioner or hate it. I once had a plastic tensioner on my Toyota truck break down towards the bottom and the piece went into the chain, around the gear and snapped it, stranding me. This happened as I got in the truck to drive home from my wedding reception. Luckily a friend is a friggin ace mechanic and had wife and I on our way home in a couple hours. Bad timing though, in more ways than one. Anyway, I'm just a bit concerned that the chain might snap a little piece of plastic off of the top or bottom. Never seen a chain restrained on both sides like that, although I haven't been into that many timing chains, so maybe it's OK and I just haven't seen it before...

 

This is off of a BMW

11311253236.jpg

 

I suppose it could very well snap the guide but the lead through the guide is only constrained in the top 3 inches. After that is's a natural flow straight down to the crank gear.

 

 

With the valve cover off you can see the whole guide so I'll be able to monitor it for abnormal wear.

 

 

The timing chain has been the bane of my existence. Since it's a linked chain it has to be a certain length. The difference in length by dropping a whole link is substantial. There are gear ratios involved and tooth count/crank snout diameter imitations as well as limitations because the K20 cams are so close together.

 

I will say though even though the last setup was noisy at idle it never caused any issues performance wise so the system is pretty forgiving. 

Unless of course you break a chunk of guide off.

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Well if you have to ask......

 

I've posted this before but with 56 pages it's easy to miss. I don't have firm pricing on it yet because I haven't machined one in a production environment. I'm telling people to have 12-14K  in the bank and depending on the build they want to do it should cover it.  There are so many variables that it will be hard to pin it down for a while. The raw castings for the head, valve cover and upper timing cover are still $4500.00. What is really up in the air is how much the machining to get it from raw casting to ready for valve work is going to cost.  I first threw a number of $500.00 and that was way off. Then I upped it to $1000.00 and that is probably low as well. I'm basing my estimates on having all the G-code proofed out and until I have machined one without a lot of tweaking I won't know for sure.

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  • 5 weeks later...

Quick update. Not much exciting happening. Waiting on the foundry to give me a tee time to pour the next head. V2 is moving along but the new owner is really tied up on other projects so there is no hurry. 

 

Here is a shot of my latest chain guide tensioner arrangement. Two custom guides and a stock L6 tensioner.

 

20170707042115-2e499092-me.jpg

 

So far this is the quietist of all the setups so far. I still have a tiny rattle between 2500 and 2800. I'm probably going to live with that for now. The Crane lobes are symmetrically ground and I have been told by multiple sources this can cause some issues with noise. 

 

This showed up today.

 

20170707042117-78e97f6d-me.jpg

 

 

S7 tool steel gun drilled blanks for the cams. I've decided to switch to S7 for a variety of reasons. Mostly because it is a through hardened core as opposed to case. This way I don't have to match the rough profile to the finished profile like I would with a case hardened cam. The machining time is the same so it just made sense. I'll still have Crane do the hardening and grind the journals.

 

Time to get whittling :)

 

Derek

Edited by Derek
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I could of gundrilled the cams for you, Thats what I do as part of my business.  Also, I would highly advise against S7, the benifit of 9310 or even 8620 is that  you can allow torsional twist as the core is not brittle.  The S7 will be hard all the way through and become brittle as it is torsional, and develop a crack potentially.  I have made many billet cams, roughing the profile is not difficult.

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1 fast Z, have you ever seen a S7 Tool steel camshaft core break due to being too brittle?

 

I've ground and supplied camshafts out of through hardened tool steel with no issues and in fact you will find many top tier motorsport engines that tool steel cams is common. This stuff is so tough I have never seen it crack from use. It is extremely tough, shock resistant and holds its hardness up to 500C. You can also run a decent bit more cam lobe surface stress on tool steel over a carburizing steel. 

 

Hell I've seen tool steel cams out of pushrod v8's that have taken hits from a thrown rod without major damage and are still useable. 

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Here is how I decided to switch to S7.

 

It was first suggested by the engineers at Crane. Not so much because I needed the strength but because of the ease of manufacturing. Cranes selection of K20 lobes blows. But they are right across the state from me and they have done great work on the cams so far.  In order to get the pricing down on the cams I need to do some sort of limited production on them. Setting up to do 2 at a time isn't going to cut it.

 

The steps with 8620 are at a minimum:

 

Copper plate. This is outsourced since Crane no longer does it in house.

Pre grind all of the areas that get hardened. This removes the copper. Since the lobes get ground they need some sort of profile to be chosen. That profile should be fairly close to the finish grind. This is the biggest issue that caused me to switch.

 

Send out for heat treat. Again this is outsourced to a separate place.

 

Cam bearing journals and front snout are then finish ground by Crane.

 

Now here is the path on S7:

 

Crane sends out for heat treat.

Cam bearing journals and front snout are then finish ground.

Lobes are already shaped by me before they go to Crane and are through hardened and ready for finish grind by whomever does it.

 

Before I committed to the S7 I did some research and consulted with Schneider cams and Whitley Tune. The answer I got was basically the same. Probably overkill for this application but will work fine.

 

I also saw this article from PRI magazine dated January 2015

http://www.bluetoad.com/article/Profiling_The_Newest_Racing_Camshafts/1892565/240066/article.html

 

What got my attention was this:

 

Totally Tool Steel 

The industry is already moving in that direction. “We have found S7 tool steel to be a good fit for some applications,” said Partridge, “not so much because it is stronger than 8620, but because the substructure of the material will support more load. Top Fuel and Nitro Funny Car cams, for example, need that additional substructure especially because of the load on the exhaust lobe.” 

And McInnis added how “a high-strength, tool-steel core allows a larger gun drill through the camshaft, which reduces rotating mass and, with it, parasitic losses in power output.” 


Tool-steel camshafts are not only more resistant to wear, but “stiffer, both in beam and torsional strength,” Knight added. “And they are not brittle, they are just very, very tough. One Alcohol Funny Car team bounced three connecting rods off of one, and we just straightened it out a few thousandths, touched up the lobes, and sent it out to run again.”

 

 

All of that made me feel that S7 was a better choice for this application than a case hardened steel. Now if someone really wants 8620 I'm happy to make it but it's going to be a custom run and be pricy.

 

And there is the tale of the S7 cams:)

 

Derek

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  • 2 weeks later...

And Baby makes three:)

 

20170707042120-dcc9647a-me.jpg

 

Just picked this up from the foundry. Poured it a week ago and it had to go through heat treating. Everything came out great. Next stop is X-Ray inspection and then I can begin machining.

 

A few more under my belt and I'll start to breathe easier. 

Edited by Derek
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" McInnis added how “a high-strength, tool-steel core allows a larger gun drill through the camshaft, which reduces rotating mass and, with it, parasitic losses in power output.”

 

And people thought I was joking referring to losses from camshaft mass... To them I now say "Mnyaaaah!"

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  • 3 weeks later...

Been a while since I updated so I guess it's time for a big dump.

 

Are we still doing phrasing?

 

So a whole lot has been going on behind the scenes as far as the processing of the raw castings and some big design changes. First the processing. I'm always reading about casting and cylinder heads. I was researching different methods of controlling casting shrinkage and porosity and stumbled across an article on how Edlebrock casts their racing heads. Not their production heads. They mentioned that they offer an optional service called "Hot Isostatic Pressing" Or HIP. The HIP process consists of heating the casting to a set temperature in a pressure vessel and then pressurizing it to as much as 30,000 PSI. This basically compresses all of the porosity  out of the metal. One comment from the article that stood out was it makes the casting almost as dense as billet. It's so much denser that they had to adjust all of their machining speeds and feeds lower to accommodate the extra hardness. I'm now setup with a HIP provider and just had the last casting done. Because it's a heat process the head needs to be heat treated afterwards. It's currently at the foundry in the furnace as I type. I'm pretty excited about this since porosity is in every casting to some degree. You control it the best you can but there is always some. 

 

Going forward I'll most likely forget about X-raying the castings since if there is a large amount of porosity it will show up as a depression or a complete blow. I'm also hoping to do away with resin impregnation since there should be no leaks. I'll know better on that after I finish machining and do the pressure test.  

 

And now for the design changes. I have worked out how to implement Variable Cam Timing. This was no easy thing for sure but I'm all but certain it will work mechanically.  The basic idea is I'm sticking with the KA24 lower chain and Idler. But I'm modifying the idler to accept a Honda K20 steel exhaust cam gear. This will allow me to run a shortened Honda chain and gears from a K20. Here is a picture of how that looks.

 

20170708030025-ee43290b-me.jpg

 

The head has been made wider at the front, the valve cover is 1/2" higher to accommodate the gears and the timing cover has been redone. It's wider plus it has a solid section at the bottom front that will become the manifold for the VCT valve. In the above picture you can see the oil inlet valve to the left and then the advance and retard circuits on the head. The Honda exhaust gear gets the center machined out and 6  5mm holes are drilled through. The KA24 idler gear will have the outer gear machined off to match the bore on the Honda gear and 6   5mm holes drilled and tapped to hold the two together.

 

 

Here is the timing cover and VCT in place.

 

20170708030024-df142334-me.jpg

 

 

The VCT is from a V6 Nissan and should work fine as it has the same port sizes as the Honda.

 

I've made the #1 tower wider to accept the grooving for the oil circuit.

 

20170708030026-2dec35d8-me.jpg

 

 

Since VCT and sequential injection require trigger wheels I redesigned the cams and rear tower. This is now the thrust area. It uses the stock Honda washers and bolts. The washers will work for Non VTC but will need to be customized for VCT and or sequential.

 

 

20170708030026-0d29217f-me.jpg

 

 

 

And here it is in all it's glory. 

20170708030021-bddb4b8d-me.jpg

 

I raised the valve cover up a half inch and then brought the plug valley back down a half inch since it has to be at a certain level. It actually looks better since the relationship between the cam cover and valley is more pronounced.  I added bosses under the valley to accept screws for the the Honda COPs. There are two. One fro the wire pointing forward and one pointing rearward depending how you want it to look.

 

Now for the nitty gritty.  All of the castings and cam towers are currently sporting these modifications including the one I'm doing now. So I guess that officially makes it V3. The non VTC cam shafts have been redesigned to work with the new towers but still use the KA24 upper timing set. If you want to convert from non VTC to VTC you will need new cams and all the other VTC specific bits.

 

I have no plans at this time to actually make a running version of this myself. My main goal was to make sure that the parts I'm selling now will work with VTC if someone is brave enough to do it. My best guess is you are going to add 3-4 K by the time you have all of the bits working. There is a lot more to it than what you see here. ECU, sensors, plumbing etc. Not to mention I have no idea if the L6 pump will deliver enough volume to even make it work. 

 

But it will fit on the head:)

Edited by Derek
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