Restoring the Cordoba - Part 3: Machine Work
|Part 1||Part 2||Part 3|
The first part of the engine I machined was not the block, but the
valves. I did this because they were easy, available at the time, and
my rotating kit had not yet arrived. In order to machine the cylinder
block the piston size must first be measured, then the cylinders can be
bored and honed to size with the proper tolerances.
After receiving the parts, I measured the pistons with a micrometer and recorded the diameter. All were 4.029 inches, with a variance of up to one thousandth. I then bored each cylinder to 4.024 inches, and then honed each cylinder to size in relation to its corresponding piston. This way each cylinder is up to two thousandths larger than the piston within, which is the spec for Keith Black hypereutectic pistons. After honing, I mocked up the rotating assembly to measure piston-to-deck height. It was here that I ran into a problem.
My pistons are a high quench design, which means they have a extra tall step to produce extra quench inside the cylinder. Up to a certain point, high quench causes the air/fuel charge to compress inside a specific area of the combustion chamber, leading to less chance of detonation, higher efficiency, and ability to run less advanced ignition timing, which frees up power and produces higher mileage with lower emissions while running a lower octane fuel. The problem I ran into stemmed from how deep the piston face was in the bore, and how much the step protruded above the deck.
Generally, for a performance engine, you want the pistons at zero deck. This means the face of the piston is at the same height as the deck surface in order to produce the highest amount of compression. In an emissions engine, like this build will produce, you don't want so much compression, as that would produce higher NOx emissions and potentially fail the vehicle on the smog dyno. My pistons, as measured, were 0.105 inches down in the bore on the face, and 0.076 inches above on the step. Plugging the numbers into a compression ratio calculator gave me a ratio of 7.5:1, a whole point less than what I started with! This caused me great distress for about a week, as I mulled over how to raise the compression without milling material off the pistons, which would have necessitated rebalancing the crankshaft, or milling an excessive amount of material off the block deck and the head surfaces. I finally figured out that I could get close to my goal of 9.3:1 compression by removing 0.040 inches off the deck, 0.050 inches off the head surface, and using a 0.028 inch thick head gasket. However, just to be sure, I called KB Pistons to confirm.
As it turns out, my pistons were almost completely within spec. They are designed to run approximately 0.095 inches down, with the step rising above the deck 0.080 inches. This will produce 9.0:1 compression in a head with a 72cc chamber volume, which are what my heads currently are. If I had gone through and milled off that much material, I'd be looking at a compression ratio of about 12:1, which is far too much for California 91 octane pig piss gasoline, much less 87. So instead, I'm going to mill 0.015 inches off the deck, 0.015 off the heads, run a standard 0.022 inch thick head gasket, and get about 9.4:1 compression, enough for some good power output will still staying within the realm of pump gas.
I also took my miscellaneous bead blasted parts and painted them Rustoleum glossy black. I'm going to paint the engine itself Chrysler Blue, and I think having glossy black accessory brackets, pulleys, and the like will look quite nice.
|This is a valve refacing machine. The valves are secured in the chuck on the left and spun between 150 and 300 RPM, depending on the valve size. As they rotate, they are brought into contact with the grinding wheel in the middle, and passed back and forth until the face of the valve is ground down to fresh metal. Caution must be taken when using this machine, as taking too much off the face will lead to a thin valve margin, which does not allow adequate heat transfer through the valve head and up into the stem, where it can be transferred into the head. An overheated valve is an unhappy valve.|
|Close up of an intake valve. This particular valve is from a Chevy engine, as I took these photos after I had finished all the machine work.|
|How the valve is secured in the chuck.|
|The machine controls.|
|The valve is cooled and kept clean by a constant stream of lubricant. In this case we're using automatic transmission fluid.|
|The valve is brought into
contact with the grinding wheel. On a typical domestic engine,
whether it's Ford, Chevrolet, Chrysler, AMC, what-have-you, the valve
face is typically 45 degrees. The valve seat is ground or cut to
46 degrees. As the valve and seat mate repeatedly over the first
few hundred miles, the interference fit is worn down and a perfect seal
is formed by the pounding action of the valve as it closes.
A stock three angle valve seat cut, and a valve face of 45 degrees will produce decent air flow, but for higher air flow a back cut on the valve face is often a good idea. I ground my valves to 45 degrees, then went back and ground a 30 degree back cut. This smoothes out the path the air must take when filling the cylinder, and the higher the air flow, the more efficient the engine.
I intend on going back and putting an even further back cut of 15-20 degrees on the valves.
|Polishing an intake valve.
While not required, polishing the valves reduces the amount of surface
area available for carbon to attach to, causing carbon build up which
leads to higher emissions, lower performance, hot spots, and possible
detonation. The reflective surface finish also reflects radiant
heat back into the combustion chamber, which produces more power and
keeps the intake valve cool.
It takes approximately one hour per valve to get it to a mildly reflective surface finish. I start by using a paint stripping disc in a power drill, followed by sanding with progressively finer grit sandpaper, finally ending with 800 grit crocus cloth.
It is not for the weak of hand.
|The valve on the left has not been polished. The valve on the right has been polished.|
|All the intake valves have been polished. The exhaust valves will also receive a similar treatment, though not to the same extent.|
|The Kwikway boring bar. To the left is a Rottler boring bar, but I prefer using the Kwikway. It cuts a bit conservatively, even if set exactly to the desired bore, and does not require the block to be removed in order to machine the opposite bank. Instead the only action required is turning the hand crank on the right, and making sure the block is square to the top table.|
|The block is secured to the boring bar.|
|This is the bore micrometer. The desired bore is set on the micrometer, which is then used to set the cutting bit into position.|
|The cutting bit.|
|Setting the cutting bit depth. The bit is inserted into the head, and the micrometer sets it into position, where it is secured by tightening an Allen head screw on the side of the head.|
|The cylinder on the left has been bored. The cylinder on the right still needs to be bored. The rust is merely a light surface rust, and will be totally removed by the boring action.|
|Action shot of the cutting head.|
|The cylinder has been bored.|
|The Sunnen CV-616 automatic cylinder hone.|
|The honing head. Adjustments are made by rotating the dial on top of the head, and specifying the amount of material to be removed on a ring below the dial.|
|A small sampling of the honing stones. They come in coarse, medium, fine, and deglaze. They are placed on top of shims, which are calculated by measuring the cylinder with the supplied tool.|
|The hone information gauge,
dwell control knob, and emergency stop button. The gauge shows the
current load on the hone. For a typical hone job the load should
be between 40 and 60. Any higher and you're trying to remove too
much in one go.
The dwell control knob indicates how many cycles the hone will dwell at the bottom of the cylinder. As the hone moves up and down, the very bottom of the cylinder tends to receive less machining than the middle and top, and will therefore be undersize. By having it dwell a number of cycles, this can be corrected.
The emergency stop button is self explanatory.
|The block is mounted in the hone.|
|A torque plate has been
installed. A torque plate is a chunk of metal that simulates the
weight of a cylinder head attached to the block at its proper torque
rating. If a torque plate is not used, the cylinders will be still
be honed perfectly round, but when the head bolts are torqued to their
torque rating, the force will distort the cylinders and cause them to be
out of round, leading to poorer ring seal.
These bolts were torqued to 105 lb/ft, as per factory specs.
|Action shot of honing.|
|The cylinder on the left has just been fine honed. The cylinder on the right is only medium honed. Note the difference. This surface finish would be fine if I were running chrome or cast iron rings, but I'm running plasma moly rings, which are considered the best type of ring for a high performance type engine. These seat well, provide excellent sealing, and have very long life and anti-wear characteristics, all of which I want in this engine.|
|All the cylinders have been fine honed and deglazed. The cross hatch looks perfect, and the cylinder walls are smooth. This surface finish will ensure excellent ring seating with plasma moly type rings.|
|The piston is mocked up in the bore.|
|Number six piston at top dead center.|
|Close up of number six.|
|Zeroing the dial gauge.|
|Measuring the piston height.|
|Measuring the step height.|
|Checking the rod bolt to cylinder bore clearance. It was completely satisfactory at about an eighth of an inch.|
|Another view of rod bolt to cylinder bore clearance.|
|A small sample of the newly painted parts.|
|Smog pump and crank pulleys.|
|The kickdown and throttle bracket.|
|A head is affixed to the decking jig, and is ready to be leveled and decked. On these heads I am taking about fifteen thousandths of an inch off the surface, so as to bring the quench pad down closer to the top of the piston, and to lower combustion chamber volume. The heads originally checked out at 70ccs; after decking they'll be around 68ccs, good for a two tenths of a point of compression gain.|
|The head is leveled with a very accurate
spirit gauge. Each graduation represents two thousandths of an
inch of imbalance. To set the level, the gauge is set on the
decking machine table on two axises and the measurement is noted.
Then the gauge is placed on the head and set to the same measurements.
The head is first leveled on the back-to-front axis.
|Then it is leveled on the side-to-side axis.|
|These are jacks. They are adjusted by screwing them in or out. Even a quarter turn can dramatically affect the level of the head.|
|The milling head. Each of the cutters must be level with each other. In this shop we just set it once and forget it.|
|The adjustment knob.|
|Action shot of the milling head.|
|Freeze-frame shot. Here you can see the head has made contact, and is removing about three thousandths worth of material as a base cut.|
|The entire head has been milled, as evident by the clean surface finish.|
|After cutting, a roughing stone is passed
over the head surface to knock off the burrs and high spots. This
produces the somewhat dirty appearance of the deck surface.
Unfortunately, this machine sits on highly unstable ground and is very finicky, and I was not familiar with its quirks until I had fully decked both heads. So the heads are not entirely square in their geometry. The adjustment knob is also quite loose and inaccurate. This resulted in a major cut being taken when the knob was set to a minor cut, and took a chunk out of the corner of the head before I shut down the machine. I then corrected the adjustment, but there's still a ridge of uneven heights in the corner. Luckily it's not on a very important section, and won't see coolant, oil, or compression pressure.
Will this adversely affect the engine's performance? No. Is it annoying and unacceptable in a high performance build? Very much so. Always triple check your measurements, and be sure the ground underneath the machine shop isn't just sand.
|The block is then set up to mill the deck surface. I'll be taking approximately fifteen thousands off the block surface as well, in order to bring the pistons further out of the hole and closer to the head quench pad.|
|This is a jig to properly level the block. It's attached to the mounting rods and secured to the block, and the gauge is placed on the jig instead of the block. However, by this time I had learned the quirks of the decker, and did not use the jig.|
|New thick wall bronze valve guides have
been installed in the heads, as the stock valve guides were permitting
oil to seep into the combustion chamber. Unfortunately I did not
get any photographs of the entire drilling or installation procedures,
which are fairly interesting. Next time.
Thick wall bronze guides are the best type of guide available. The bronze retains oil extremely well, has a good surface finish, and can be removed later if necessary. Their service life is usually about a hundred thousand miles, so for this engine I won't have to worry about servicing them for quite a while.
|This is a valve guide gauge. Incredibly accurate, and incredibly expensive. It measures in increments of two ten-thousandths of an inch.|
|The gauge is inserted into a guide to check for proper clearances. On the intake valves, one-to-two thousandths is acceptable. On exhaust valves, two-to-three thousandths of clearance is desired, as they see more heat than intakes, and need more clearance for better oiling and expansion.|
|This is a valve guide hone. The proper size mandrel is attached, and a stone is inserted. It's then chucked up in a drill, or the chuck on the valve guide machine.|
|It's then inserted in the valve guide with a bit of lube, and spun to hone the guide to size.|
|After the valve guides were installed and sized, and the valve seats cut, I brought the heads home to port and polish them. This is the head as it came from the decking machine.|
|Note the rough surface of the combustion chambers. Carbon would stick to this surface extremely easily, and it's not the greatest surface for heat reflection.|
|In order to polish the whole head, I simply took a paint stripping disc and went over the entire surface. It's hard to get in the nooks and crannies, but I did an acceptable job.|
|See how smooth the chambers are now? Carbon will have a hard time sticking to that, and the shiny finish will reflect more heat back into the chamber, increasing power and efficency.|
|This is a basic head porting kit. It
comes with many different abrasive types, such as cartridge rolls, flap
wheels, and polishing heads. This kit has two different grits,
coarse and fine.
The abrasives are chucked up in an air die grinder, which is run at about half power for better control and longer abrasive life. The heads are then gone over to polish up all the air flow surfaces.
|These are the intake ports. Notice all the casting flash and small size, as well as the pushrod tube pinching the port. This will all be ground off and/or smoothed down in order to promote higher air flow.|
|First I gasket match. In order to do this, I mark up the ports with a dry erase marker.|
|Then the intake gasket is bolted to the head.|
|Where ever the head shows up inside the gasket port will either be removed or smoothed out. So I don't damage the gasket, the port outline is scribed on the head.|
|A poor photo, but it shows the scribe line.|
|I also touched up the exhaust crossover.
There are no photos of the resulting ported and polished head, simply because I forgot to take them. However, these are the modifications I did to the heads:
Gasket matched the ports.
Smoothed out and polished the pushrod pinch area for greater air flow over the hump.
Polished the first half inch of the port, leaving the rest of the port rough to promote greater atomization of the air-fuel mixture.
Unshrouded the valves.
Unshrouded the spark plug boss.
Increased the surface finish of the entire combustion chamber.
Smoothed and polished the entire exhaust port and runner to promote greater exhaust flow.
Deburred all sharp corners and surfaces.
|Half of the valve train has been installed. On the left you can see the pushrods and rocker arms.|
|Shot of the passenger side valve train.|
|The driver side valve train. No pushrods yet.|
|These are rocker arm shims. Since I milled a total of thirty thousandths off the head and block, the pushrod geometry was changed. I did not want to purchase new pushrods or adjustable rocker arms, so I instead used thirty thousandths thick shims to raise the rocker arm shaft back to roughly its original position. This ensures proper geometry, and proper lifter preload.|
|The push rods sit in the lifters, shown in the middle of the photo, and go up through the holes in the head to sit in the rocker arm, shown at the bottom.|
|Shot of how the pushrod sits in the rocker arm.|
|This is how the lifter rides along the camshaft. This is a hydraulic flat tappet camshaft, which means the bottom of the lifter rides directly on the surface of the cam lobe. The lifter bottom is slightly radiused to promote spin, and the cam lobe is slightly offset to further promote spin. If the lifter doesn't spin, it will quickly wear the cam lobe down. The black grease is molybdenum grease, required on flat tappets for break-in.|
|All the rocker arms are contacting the valve stem tips.|
|A camshaft retainer plate meant for a mid-nineties Magnum V8 fits the older LA style V8s just fine. This plate also has a spring loaded timing chain tensioner, which ensures proper chain tension throughout the life of the engine. I also used a new double roller type timing chain for extra reliability. The fuel pump eccentric is bolted to the camshaft after the timing gears are installed.|
|The intake manifold, timing cover, and water pump are bolted to the engine...|
|...As well as the oil pan.|
|Now at home, the engine is prepped for painting.|
|Three coats of Duplicolor blue later, and the engine looks brand new.|
|The carburetor mount and EGR valve mount.|
|The exhaust ports.|
|The head bolts have been torqued down and the valve covers installed, as well as the fuel pump, dipstick, distributor, and water neck. The throttle linkages have also been added.|
|Close up of the water neck and throttle return spring bracket. The throttle linkage can also be seen toward the back.|
|Fuel pump and dipstick. The water neck and dipstick are the only chrome items on the motor, simply because they aren't really available any other way. I'm not really a fan of chrome, but I grew to like the dipstick and water neck because they're not garish and obnoxious.|
|Exhaust ports and head bolts. They were added after painting, which is why they're still black.|
|Throttle linkage and distributor.|
|Throttle return spring bracket. This is held in place by the intake bolts.|
|Throttle linkage, also held in place by the intake bolts.|
|Carburetor mount. The chrome pipe plug in the right side was installed to replace the rubber plug that was originally there. Without that plug, there would be a massive vacuum leak into the EGR system.|
|Thermostatic choke well. This is where the choke element is installed, as it sits right above the exhaust crossover.|
|Distributor, with the rotation kindly marked on the intake just in case I forget.|
|From left to right: intake manifold thermal vacuum valve, EGR valve, and radiator thermal vacuum valve.|
|The EGR valve, along with its gasket and assortment of orifice washers. These restrict the amount of exhaust gas flowing back into the motor.|
|An orifice washer is placed in the valve.|
|The washer is then staked into place with a center punch.|
|Thermal vacuum valve. Above a predetermined temperature, 75 degrees in this case, this switches on vacuum to the next switch in the EGR circuit.|
|Installed EGR valve. This lets exhaust gases flow back into the motor for reburning and to lower the combustion temperature in order to reduce NOx emissions.|
The engine is now virtually completely assembled. All that remains is
the carburetor, spark plugs, plug wires, cap and rotor, and reattaching the accessory brackets and
flex plate. However, I will have to use a flywheel first in order to break
in the motor, as I want to do that out of the car, so I won't have to yank it
back out should anything go wrong.
After the motor is entirely finished, work can start on the car itself.
|Part 1||Part 2||Part 3|