Got all the intake valve work done.

Got a little carried away with the machine allowance on the intake side! Had to take it down almost .375″.  I had to leave that wall around it because the mill was hitting the side of the head. You can see where it nicked the intake bolt boss.

Every port looks just like this. Man I like digital mold making. The accuracy is just amazing.

Well today was a big and stressful day. I got all of the exhaust valve work done. Drilled and reamed the exhaust valve guide holes and machined the valve spring bosses.

Everything seems to be working out as I planned.

This is the best part. The bores came through right where I needed them to. After I had printed the sand molds I realized my valve angle was off by half a degree. That’s why the bore of the valve guide is not centered on the boss. Future heads won’t even have that boss on there. I’m not really sure why I put it in  as there is plenty of support for the guide without it.

Found time to map out the exhaust ports. They were all within .005″ or .006″ of where they should have been. A lot of that may have been the toughness of the casting affecting my touch probe accuracy. I can tell you that is pretty accurate for a sand casting.

Here is a shot of me taking a skim pass for port matching to the flange.
You can see I have a little hand work to do on a couple of the combustion chambers.Exhaust

Exhaust side all done

Tomorrow I start on the valve guide bores.

So I got the top surface done.

I started out with a modified spark plug stop to use as a gauge. I used the end of the threaded rod that goes up through the head to touch off from. This let me know where I was in relation to the combustion chamber.

I surfaced the top,did all the cam tower work, spot faced the head bolt bosses, bored the spark plug tube bosses to the correct depth, tapped the bosses for the tubes and drilled the oil gallery.

Had to relieve one side of the cam towers for the ARP washers to clear.

Set a few towers on for fun.

Made some progress today. Got the chambers mapped out and ran a finish pass over them. I designed the chambers to be “as cast’ but I knew that was a mistake as soon as I saw the casting. Since I didn’t have any machine allowance to work with I did the best I could. There are a few spots I’ll have to hand work. I finished the surfacing and recut the water passages to make sure they were in the right spot. They were off a hair. Really happy with the quality of the casting so far. I engineered the gating system to prioritize the combustion chambers and bottom of the head. The metal is super clean so far.

I’m going to need a lot of piston clearance for this to work 

Deep drilling the head bolt holes. This stuff make my butt hole clench.

Bottom all done. (I think)

This is the ground flat bar that I’ll use to set the rotational angle when I roll it over. That way I’m indicating off of the bottom surface.

I had some imperfections in the bottom of the casting that I needed to weld up. I made a light cleanup pass to make sure I got everything filled.

Next is mapping out the combustion chambers to see exactly where they ended up. Castings shrink when they cool. Although there are formulas to use as guidelines it’s still a bit of a guessing game. All the core sand inside makes it especially hard.

So far so good!

Although I was really happy that I got a good casting the first time this meant I had nothing to practice on. I decided to do a plastic mockup so I could test out my valve angles. head bolt locations and intake and exhaust bolt holes

I decided to do the head with a 4Th axis instead of building fixtures. This can save a ton of time when you are prototyping.

I used the original 3D model to carve a single cylinder.

I carved the combustion chamber and drilled the spark plug hole. I then used that hole to locate where the cam towers needed to be mounted.

I then worked off of the rocker shafts to get the valves in the right spot.

As you can see it took a couple of tries to get it right. And that is why I did a mockup. We do it nice cuz we do it twice!

Valves ended up where I needed them to.

This is by far the most complicated casting I’ve ever designed. And was really surprised that it poured on the first try.

Here is the 3D printed water core, ports and combustion chamber.

These are the 3D printed parts all assembled and being incorporated into the surrounding mold. I design this way to save a ton of money.

After the pour.

If you want an idea of how detailed 3D printing sand can be check out this lettering.

Now I could finish modeling the front and back of the head.

Next the front timing cover. The water outlet exits the head in the front and makes a 90 degree turn through the timing cover where the thermostat housing will mount. This design has been one away with as it was deemed that it wouldn’t provide enough flow for turbo cars. It was too late for this head though.

Now the valve cover. The K20 cam towers kind of dictated the overall size but I was still able to get the styling I was looking for. I was originally going to machine in the lettering but I put it to a vote and this design won out.

After talking with Jeff about his testing on coolant flow I decided to get the most out of the 3D sand printing process as I could. I designed a water jacket that would be pretty hard to duplicate traditionally. There is a lot of surface area so hopefully there will be large improvements in cooling.

Here is a nice shot of the intake and exhaust cores, water core, and upper tensioner. You can see where the cross drilling will go to supply oil to the head, tensioner and idler gear lube.

There will have to be additional oil supplied to the last three cam towers as the single feed in the front won’t cut it.

Here is a cross section of the head. The cut plane is through the center of one of the intake valves so the ports look a bit off. There is machine allowance on the bottom so the combustion chamber is a little larger than it will be after surfacing.

The design work on the head is pretty much done at this point so it’s time for mold design.

Jeff and I had a long conversation about pros an cons of various designs. The preference would be a single chain so I ordered up a K20 set to see if it was workable. NOPE.

Lower timing gear is too small to bore out to fit the L6 crank snout Back to the drawing board.

I decided to give the KA set a try. I decided the Altima set would be a good choice as it’s only a single row chain up top. With the roller rockers I don’t think you need a double row. But there is nothing stopping people from using a double row if they feel like it.

I did a rough mockup on a piece of wood mounting all the pieces. I used my router to plot out the locations of the parts and drill the mounting holes. This gave me a point of reference.

Then I machined a chunk of plastic so I could actually mount it to the block.

You can see I’m trying to incorporate the KA guides and lower tensioner but that won’t happen without a new lower timing cover.

Here is the lower section with stock modified L6  components. The only tricky bit is I need to remove one link from the chain. I think this is a workable solution.