Twin cam head for the L6 from Derek at Datsunworks

[Derek]

Update time.

 

So I wanted to update the thread to reflect a change I made to the casting process. As some of you may remember I started using a method of conditioning the castings called Hot Isostatic Pressing. The HIP process heats the head to like 700 degrees F in a pressure chamber and then Argon gas is pumped in at around 25K PSI. This crushes the micro porosity in the casting and makes for a much denser part. Unfortunately after two rounds of heads I have come to the conclusion that even the slightest difference in porosity can lead to pretty big differences in the size of the heads. It was making the machining much more difficult than it needed to be. The reason I went this way in the first place was I wanted to make sure the combustion chambers were dense.

 

So I opted to go with a more traditional method of metal control which is using something called a "chill" Chills are usually metal and their function is to cool the aluminum in a specific area. I have been using an external steel chill in the front of the head since V1 to control the metal shrinkage since it is so thick there. Chilling the metal makes for better quality. Combustion chamber chills are nothing new I just wanted to avoid them if I could. Well I couldn't  

 

I chose to make them from bronze for a number of reasons. Thermally they will do what I wanted and manufacturing was a lot simpler than steel. 

 

I made a pattern of the rough shape I wanted and had them cast in bronze. 

 

 

 

I need one for each chamber but they are reusable as long as they don't get damaged. 

 

And like magic they are machined.

 

 

The shape of the chill is the same as the combustion chamber shape that I have been using all along.

 

 

Using chills required a redesign of the ports, water jacket and the external parts of the mold since it could no longer be 3D printed as a unit. It became a little more like a traditional mold in that we now have to hand set the port cores. The round buttons on top of the chill is what locates the 3D sand cores.

 

 

The ends are supported and located with rods that pass through the mold. This provides for a very accurate placement of the core.

 

We poured a test head and everything went great. No visible defects.

 

 

 

Since it was such a large change I had the head X-rayed to make sure there wasn't any defects. Everything looked good.

 

 

 

Hopefully this is the last big change to the head casting procedure. The HIP process was really cool but ultimately it induced too much uncertainty in the machining and it really ran my anxiety levels up.

[AydinZ71]

5 hours ago, Derek said:

Update time.

 

So I wanted to update the thread to reflect a change I made to the casting process. As some of you may remember I started using a method of conditioning the castings called Hot Isostatic Pressing. The HIP process heats the head to like 700 degrees F in a pressure chamber and then Argon gas is pumped in at around 25K PSI. This crushes the micro porosity in the casting and makes for a much denser part. Unfortunately after two rounds of heads I have come to the conclusion that even the slightest difference in porosity can lead to pretty big differences in the size of the heads. It was making the machining much more difficult than it needed to be. The reason I went this way in the first place was I wanted to make sure the combustion chambers were dense.

 

So I opted to go with a more traditional method of metal control which is using something called a "chill" Chills are usually metal and their function is to cool the aluminum in a specific area. I have been using an external steel chill in the front of the head since V1 to control the metal shrinkage since it is so thick there. Chilling the metal makes for better quality. Combustion chamber chills are nothing new I just wanted to avoid them if I could. Well I couldn't  

 

I chose to make them from bronze for a number of reasons. Thermally they will do what I wanted and manufacturing was a lot simpler than steel. 

 

I made a pattern of the rough shape I wanted and had them cast in bronze. 

 

 

 

I need one for each chamber but they are reusable as long as they don't get damaged. 

 

And like magic they are machined.

 

 

The shape of the chill is the same as the combustion chamber shape that I have been using all along.

 

 

Using chills required a redesign of the ports, water jacket and the external parts of the mold since it could no longer be 3D printed as a unit. It became a little more like a traditional mold in that we now have to hand set the port cores. The round buttons on top of the chill is what locates the 3D sand cores.

 

 

The ends are supported and located with rods that pass through the mold. This provides for a very accurate placement of the core.

 

We poured a test head and everything went great. No visible defects.

 

 

 

Since it was such a large change I had the head X-rayed to make sure there wasn't any defects. Everything looked good.

 

 

 

Hopefully this is the last big change to the head casting procedure. The HIP process was really cool but ultimately it induced too much uncertainty in the machining and it really ran my anxiety levels up.

Really phenomenal work Derek! Hoping someone I know near me can afford a unit so I can take a closer look. We are all appreciative of folks like you pushing the design envelope on our L-series motors. I find the metallurgy fascinating, as my knowledge on cast and machined AL is quite limited. Is there a specific alloy of AL you are using it is it proprietary? 

[Derek]

5 hours ago, AydinZ71 said:

AL is quite limited. Is there a specific alloy of AL you are using it is it proprietary? 

 

It's A356 heat treated to T6.

[AydinZ71]

3 hours ago, Derek said:

 

It's A356 heat treated to T6.

Aaaah! Interesting! Did a little research. T6 is the same harness I’m used to working with on 6061 billet parts. I bet the shrinking is much harder to deal with on AL than on Steel. 

[Derek]

8 hours ago, AydinZ71 said:

shrinking is much harder to deal with on AL than on Steel. 

 

The casting shrinkage during solidification is pretty predictable and repeatable. The shrinkage from the HIP process on the other hand was really tough to predict.

[AydinZ71]

4 hours ago, Derek said:

 

The casting shrinkage during solidification is pretty predictable and repeatable. The shrinkage from the HIP process on the other hand was really tough to predict.

I work with a few engineers at Toyota’s technical center. I could ask them the next time I speak with them. I’m sure a general discussion wouldn’t be proprietary. We work on H2 vehicle fueling facilities and protocols.

 

Do you plan on doing the final machining with a CNC or by hand? Manual for the prototype? You can tell what’s happening to the metal based on the resistance at the cutting surface. Always helped me with my proto designs. It’s been 10 years though... 

[Derek]

Well the HIP shrinkage is a direct result of the porosity in the metal. I suppose a foundry with more sophisticated process control could manage micro porosity better but that is leagues above the people I work with. The last batch of four heads we did were poured one right after the other as fast as we could and they all shrank at different rates.  At this point it's not a problem I need to solve since I've made the transition to chills. Thanks anyway though.

2 hours ago, AydinZ71 said:

Do you plan on doing the final machining with a CNC

 

All the machining is done with CNC controlled machines. Although they are converted manual machines they get the job done.

 

[DuffyMahoney]

Does this mean you can now have the head CNC ported?  

[Derek]

7 minutes ago, DuffyMahoney said:

Does this mean you can now have the head CNC ported?  

Well a capable shop could have done it before if they wanted to take the time to do it as a bespoke head but yes this opens up the possibilities for CNC porting.  

[DuffyMahoney]

1 hour ago, Derek said:

Well a capable shop could have done it before if they wanted to take the time to do it as a bespoke head but yes this opens up the possibilities for CNC porting.  

Or roughly cnc porting and hand finishing.  The Cnc port work coming out is amazing.  

[Derek]

Story time.

 

As many of you who have followed along for a while know the timing chain arrangement has been my White Whale since the beginning. I knew I wanted to use the KA24 timing chain setup and for the most part I was able to make that work. The problem was there just wasn’t enough room to fit the pivoting slack side guide and have it pivot at the bottom like it’s supposed to. The compromise was to pivot it at the top, use a custom guide and use the bottom tensioner in the stock L6 position.  This worked but the custom guide had to be a little thin in one area to clear the lower timing cover.   Now here comes a lesson for all you aspiring engineers out there and how solutions to complex problems can be incredibly simple.

 

I was speaking to Brian at Rebello after he finished the KN20 build they did for Z Car Garage. This was the first build they did for a sub 3.2L and they decided to use my system as opposed to the more complex system they designed for for the 3.5 motors. We were discussing the lack of room on the slack side for  the top pivoting guide and he mentioned that the KA24 heads have the idler gear pushed towards the tension side more than I had mine. I agreed this was worth looking into and set about manipulating the 3D model to see what I could make happen. I found I could pick up about 19mm by shoving the idler gear over. On the face of it a very simple solution to increasing the thickness of the pivoting guide. Problem solved. But wait it get’s better.

 

As I was sitting at my work station shoving various 3D components around to see what was workable I realized a fair amount of room opened up on the top and there may be room to squeeze a tensioner up there and have the bottom pivot guide I always wanted. I contacted Tioga who is my go to person for all things OEM and he got me info on the various available external tensioners that could possibly work. The problem was they were all too big to fit.

 

Then the epiphany. Why not design my own tensioner that will fit inside the existing available envelope.  Booooooommmm.  The hardest part was that I absolutely wanted it to retrofit to the existing heads I already had out there.  It was apparent that this would work and fortunately I had a head still here  so I set about with my tried and true mockup process. A little CAD/CAM add a little old school analog, bring the analog back to digital, rinse and repeat.  I ended up with this mockup. The letter T represents where the tensioner piston is.

 

 

And here is the final product. The adjustable cam sprockets are from Tomei FYI and are really well made. The slack side guide is much more robust and the front lower timing cover fits without any modifications. The stock L6 tension side guide fits with some minor slotting and cutting. The chain angles and flow look great so I’m super happy with the outcome. 

 

The tensioner is also the mount for the upper tensioner.  The slack side tensioner uses the piston, spring, and check valve from a KA24 tensioner. The body is 6061 aluminum with a 4130 DOM (drawn over mandrel) honed sleeve inserted as the cylinder.

 

 

The front of the head has scuppers to drain the oil from the valley and the new tension block blocked the right one. I had to machine a drain into it and decided to include a dribble hole to help oil the lower chain. Probably useless and the KA24 upper tensioner pukes so much oil that I doubt the lower chain will ever run dry but I felt like putting it in.

 

 

It feels really good finally making this work and short of any minor changes this is going to be the go to chain system for anyone running a single  row lower chain.

 

PS. This is one of the original mockup picture of the timing chains and no one mentioned "You know the KA24 idler is pushed over towards the tension side more" So ultimately I'm blaming you guys for missing that.

 

 

 

Edited June 5, 2021 by Derek

[AydinZ71]

Wow this looks great!!!! Excited to see you test it out! What do you have in mind for monitoring the chain movement/reaction at various RPM’s (if any). Did you settle on the tensioner spring and cylinder design based on OEM oil pressure? How much more pressure does full oil pressure apply to it, and what is the significance of the check valve? You want to maintain the max tension when off? Can’t wait to see it running! 
 

what do you think of the Robello and ZCG folks? I have heard mixed things. Some say they are arrogant and dismissive but they could have just taken something personal. Not meant to be a shit-talking session. Just curious how they have been treating you. 

[Leon]

Inspirational work as always Derek, well done! I enjoy following along with your design process. Is there any recent footage of your heads on a running motor?

 

 

Aydin, Rebello is fantastic. They can take a long time to get things out the door and are pretty old-school but they've been thorough and accommodating to work with in my experience. They did a great job on my P90. Rob @ ZCG is incredibly into what he does. He can be intense but I respect his passion and tenacity in doing top notch work.

[Derek]

17 hours ago, AydinZ71 said:

What do you have in mind for monitoring the chain movement/reaction at various RPM’s (if any).

I have no plans but if someone wanted to they can add sensors to the back of the valve cover to monitor the cams. I have a single sensor on the intake for the VVT on my car.

 

17 hours ago, AydinZ71 said:

Did you settle on the tensioner spring and cylinder design based on OEM oil pressure?

It's the guts from the existing tensioner that comes in the KA24 timing chain kit.

 

17 hours ago, AydinZ71 said:

what is the significance of the check valve?

The spring in most cases provides more tension pressure than the oil pressure against the piston can. Max potential at 70 PSI is like 17 pounds of force. The springs I measured from tensioners come in at between 13-16 ish.  The oil is in there for damping and lubrication as much as the pressure. The check valve I'm guessing is there to help with that as well as cold starts and rattling.

 

17 hours ago, AydinZ71 said:

what do you think of the Robello and ZCG folks?

What Leon said. They are both great shops but like all artisans they have their proclivities. 

 

5 hours ago, Leon said:

Inspirational work as always Derek, well done! I enjoy following along with your design process. Is there any recent footage of your heads on a running motor?

Thanks Leon.

The only footage other than my car and 005 is the dyno pull that ZCC did.

https://www.instagram.com/p/CMKqD5BHwrr/

[rturbo 930]

I thought that ZCG car had the OS Giken head, did they build another motor?

Edited June 6, 2021 by rturbo 930

[Derek]

15 minutes ago, rturbo 930 said:

I thought that ZCG car had the OS Giken head, did they build another motor?

Yes. It's a 3.1 ish. The OS was a 3.3.   Not sure why Rob hasn't been more vocal about the results but I'm sure he has his reasons. Let's just say the owner is happy with the KN20.  Hopefully ZCG will publicly post some numbers soon as they are impressive. 

[AydinZ71]

@Leon @Derek thanks for that feedback! Sounds like the usual idiosyncratic, passionate folks like you said  Not a bad thing at all, just important to keep ones patience. Il just be humble and listen more than I speak if I interact with them. The handful who were not-so-happy happen to be big-shots themselves. Let’s say... national champions. I can see how sometimes putting two high-achieving folks in a bucket may rattle around a bit. 
 

Derek, have you had any experience sleeving an L-series for better ring life or larger bore? At some point you are certainly eating into the water jacket, which isn’t great given larger displacement = more heat. I have heard of some sleeve material requiring an overall thinner cylinder wall, which can allow for larger displacement, better cylinder cooling, and longer ring life. 
 

Always curious to hear what kind of exciting ideas you have on the horizon for our L-series engines! 

[Leon]

18 hours ago, Derek said:

Leon.

The only footage other than my car and 005 is the dyno pull that ZCC did.

https://www.instagram.com/p/CMKqD5BHwrr/

 

Mother of god, that thing F***ING RIPS.

[Derek]

6 hours ago, AydinZ71 said:

Derek, have you had any experience

No

 

Actually my specialty is pattern making and casting design sprinkled with a little machining and a lot of dreaming.  I leave the rest of that stuff to people who are far more knowledgable than me. 

 

4 hours ago, Leon said:

Mother of god, that thing F***ING RIPS.

Yea that combo has more than one person, me included, to rethink their builds. My thinking at this point is basically a Rebello style 3.2 build with offset ground LD crank, rods, and pistons. Bore the block to a safe number based on sonic testing and call it a day. 

 

For years people have been saying that the majority of the L6 power comes from the head and this is really proving it to be true. The DOHC configuration moves a ton of air without a ton of lift compared to the stock single cam heads. 

[DuffyMahoney]

Tioga knows his stuff.  

 

The whole setup looks great Derek! I want to own one someday.