After weeks of tedious preparation, the last three surfaces of the workpieces could be machined so I'd finally have something that actually resembled a pair of heads.
The simplest inboard side was machined first. With the workpiece mounted in a vise, the mating surface for the intake manifold was cut down to its finished depth. The head's top corner was then chamfered to provide clearance that will be needed later to install the manifold. My chamfering tool was actually a two flute 90 degree countersink. All my countersinks are clearly marked 90 degrees, but their side cutting angles measure 42 degrees - maybe a compromise for use with 90 and 82.5 degree fasteners?
The outboard side was machined next on the Tormach. The head was designed so this complex surface could be machined in a single vise setup, although I left open the possibility of having to skim the exhaust flange in a later setup. The half thou scallop height left by the finishing ball cutter seems to have made that unnecessary, but it will revisited after bead blasting. Since all the holes were manually pre-drilled, they were suppressed in the model used by the CAM software to generate the tool paths. This step simplified the tool paths and reduced the machining time.
The head's topside was the last and most complex side to machine. For those operations the workpiece was re-attached to its dowelled fixture plate and clamped to a ten degree angle table. The excess stock on the top of the head was manually removed before turning the Tormach loose on its interior. Total top side machining time was five hours per head.
Pads for the 8-32 head bolt heads were manually counterbored with an end mill and a set of hardened steel washers custom ground for them. The temporary threads in the holes were reamed out, and the fit of each head was verified on both sides of the block with all head bolts in place. The rest of the fastener holes were then tapped.
The coolant return passage(s) through the intake manifold side will be drilled later when the intake manifold's coolant scheme is figured out, and the intake and exhaust ports will be drilled through the valve cages after they're installed.
Laser surgery repaired the damage left by my cataract surgery, and I finally have good vision in my right eye. After my experience with cataract surgery, I may just live with the one in my left eye. - Terry
I haven't posted to the 289 build thread for quite a while and wanted to let everyone know I haven't abandoned it.
We had a once in a lifetime ice storm here in central Texas during the first of February that was described by news reports as an ice hurricane. We have (had) lots of tall and hefty elm and oak trees on our property with many huge limbs overhanging house, shop, and a ten year on-going backyard landscape project. The huge amount of foliage on these 60 year old trees wound up covered with nearly an inch of ice, and for two days all we heard was the sickening crackling of limbs as they broke and fell all around (and over us.) During the three days we were without power we cut the limbs into manageable pieces and hauled them away to the local recycling center. Our town estimated the storm left behind a million cubic yards of tree debris for residents to deal with. Unfortunately, while up on a roof I managed to wrench my knee and back, and that has slowed our own cleanup effort. So far, we've hauled away 13 truckloads of tree limbs and are only about half done.
I've started reviewing my earlier modeling on the intake manifold and hope to restart the build in a couple weeks when I can once more comfortably stand. Although I thought the model was 90% complete, I've run into some frustration with its coolant return scheme. Things haven't quite clicked with me on that part of the engine since life got in the way, but things will soon work their way out. - Terry
The design of the intake manifold has soaked up more time and thought than all the other pieces of this engine combined. Although I managed to complete its topside, last summer's modeling left me nearly burned out and still with no plenum or coolant design. The topside was modeled after the original Hi-Po, but its high rise carb mount has become a separate add-on in order to reduce machining time. As with this engine's other 'castings', the manifold's top surface was designed to be finished with a 1/4" ball mill, and the interwoven surfaces created by the stacked fillets became off limits for the rest of the design.
My quandary with the plenum and its associated runners was whether to scale them down from the full-size engine or to simplify and reduce their included volumes and perhaps achieve higher vacuum and runner velocities. Either would require machining a complex interior, but with the scaled approach I kept bumping into problems with my off-limits topside.
I believe George used scaling and divided his brass manifold into two pieces across the center plane of the runners. Runners and a plenum were machined into both halves that were later soldered together. After a lot of indecision and research into other model designs, I drilled my runners directly through what eventually became the manifold's 45 degree sides where they intersected a 1/2" wide central slot running the length of the manifold. The carb opening and runners were blended into the 'plenum' which was permanently closed and sealed with a JB-Welded cover.
The other issue involved the need for a path through the manifold to return coolant to the radiator from the rears of both heads. This was accomplished with drilled passages in both the front and rear ends of the manifold that were connected by a longitudinally milled trough. This trough was also permanently closed with a second JB-Welded bottom cover. Both covers were installed with .030" glue lines, and epoxy thinned with a drop or so of acetone. The acetone increased the cure time and allowed the lowered viscosity adhesive to fill the small spaces with minimum trapped air.
A SolidWorks rendering in one of the photos shows the fuel and coolant paths inside the manifold. The mysterious trough around the carb's topside opening will eventually become the reservoir for a recirculating fuel loop.
The first step in construction was to square up a 7075 workpiece. The eight 5/16" runners were then drilled perpendicularly through the sides of the workpiece. The #1 runner was unique and had to be angled to clear an internal coolant passage. The longitudinal slots for the plenum and coolant return were machined next. A ball mill blended the runners and carb opening into the plenum. After the JB-Weld cured, the bottom surface of the manifold was skimmed, and the 45 degree sides were machined. My Enco mill had just enough y-axis travel for a simple vise setup. These cuts took into account .020" head and manifold gaskets, and care was taken to make them as accurate as possible. For good measure, an o-ring groove was added around the coolant transfer passages at the rear of the manifold. The carb opening was finish machined through the topside of the workpiece.
After finish machining the manifold's bottom side, it was trial fitted to the block/head assembly using shims to simulate the head and manifold gaskets. Half thickness shims were used under the heads to account for the .010" excess deck material still on the block. Once the fit was verified, the actual head and manifold gaskets were cut from .020" Teflon sheet.
The cooling scheme was finalized with drilled passages in the rear ends of the heads to transfer coolant to the manifold. These two holes completed the head machining. Up until this point the two heads were identical, but these last two holes made them different.
The next step will be the lengthy machining of the manifold's topside. A work-holding scheme has to be worked out since there's currently no reliable way to support the workpiece for full topside access. - Terry
My original plan to support the workpiece during the manifold's topside machining was to attach it to a fixture plate using the twelve mounting holes that were earlier drilled undersized and tapped. This wasn't very well thought out, and when it came time to machine the plate I realized there weren't enough threads in the manifold's 45 degree sides to reliably hold it.
Plan B was to add a 1/16" high 'chair rail' to the long top sides of the manifold so it could be held in a vise. This eliminated the sharp edges in my original design and actually improved its appearance. More importantly it provided a pair of contact surfaces for the vise. A machined spacer raised the workpiece minimally above the vise jaws for end mill clearance. I was concerned about the tiny .055" contact patch, but any more would have intruded into the manifold's off-limits topside. After getting through the roughing passes, concerns with the setup faded, and the rest of the machining went smoothly.
My ancient XP computer's resources weren't adequate to compile the single twelve hour topside finishing operation, and so it was broken into a number of smaller operations. A fake operation that was compiled but not actually run was used to trick the software into not re-machining the finished cutout for the distributor.
In a later operation, the face of the manifold's thermostat housing was grooved for an o-ring to avoid the need for a water outlet gasket. The manifold gaskets and dummy head shims were used to verify the fit of the manifold in the head/block assembly using the actual manifold mounting bolts. Custom ground steel washers were used under the bolt heads.
The cooling system's last requirement was the drilling of vertical passages in the block to transfer coolant between the block and heads. While still set up, a series of slots were milled into the floor of the block's lifter valley. These openings along with vented valve covers should allow oil mist driven by crankcase pressure pulses to lubricate the top end roller rockers. These last steps pretty much completed the block's machining except for the excess deck material that will have to be removed after the liners are installed. Finally, with the ports plugged and the sides masked off, the manifold was bead blasted.
Except for the crankshaft and camshaft, machining of all the parts that were modeled last summer has been completed. Since I'm on a roll with the engine's 'castings', the plan is to continue on with the valve covers, oil pan, and water pump before moving onto the dreaded camshaft and crankshaft. I'd like to get the parts with the long machining times completed before the hot weather and local power outages return. - Terry
The valve covers were up next. The stock engine's stamped steel covers were functional but lack panache. Since museum accuracy isn't my goal, I thought I'd indulge in a set of 'Cobra' valve covers. In the day, these cast aluminum covers were available from the aftermarket in a variety of styles, and they were popular dress-up items for a number of Ford engines. In fact, I treated my '65 Fastback to a pair some 40 years ago.
Construction began as usual by squaring up a pair of 7075 workpieces. The filler/vent holes were predrilled and reamed and used as the machining reference for all subsequent operations. A gasket recess was machined into the bottom of the covers' mounting flange. Until the gasket is installed, this recess will keep the covers in place on the heads during testing and troubleshooting without the need for bolts.
The outside surfaces were machined using 1/4" roughing and finishing cutters, but the topside with its .075" raised lettering was designed around a 1/16" end mill. The font (bold Source Code Pro) and its size and spacing were selected especially for this cutter. The machining time on the 10 square inches of topside real estate was reduced to a reasonable one hour using Tormach's Speeder which is a 3X spindle speed multiplier for their 1100 mill. Using a .030" d.o.c. and running at 13k rpm, the tiny four flute cutter was pushed at a leisurely 9 ipm.
This was my first use of the Speeder since switching my coolant system over to a Fog Buster with Kool Mist. This combination has been working well for me, but its overspray seems to form an amalgam with fine aluminum chips that sticks to the mill's painted surfaces. It's nearly impossible to clean off, and over time the exposed painted surfaces of my mill have acquired an unsightly aluminum topcoat. The extra fine chips created by the tiny cutter running in the Speeder added yet another layer.
The covers were bead-blasted and airbrushed with satin black Gun-Kote. After an oven baked cure, the raised text and cooling fin tips were polished back down to bare metal using 220g paper. A pair of cover gaskets were cut from .015" Teflon.
Since I've made no provision in the head for a sump return, the filler cap will be largely cosmetic. However, it and the opposite cover will contain custom check valves to vent the crankcase to the atmosphere through the pushrod clearance holes in the heads. Oil film that finds its way into the space under the valve covers will lubricate the roller rockers. Inlet air for the PCV system will be drawn through a similar but opposite acting check valve located somewhere on the block. This PCV valving will be finalized later. - Terry