Thanks, I'll try that, really like the concept! John
Ford 300 Inline Six
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I like to think of it as a pressure equalization. When you first start out, the cutter is resting on the 90 degree corner of the cage. Although the cutter weighs only a few ounces, the pressure (lbs per sq inch) is very high. The cutter is driven by gravity into the cage and shears metal away to form a uniform seat as you spin the cutter with your fingers without applying any force (or pressure) of your own. The width of the resulting seat is dependent upon a couple metallurgical properties of the metal which for 544 bronze happens to come out to .005" to .007". This seat width is the point where the resulting pressure of the cage pushing back on the cutter equals that of the cutter acting under gravity alone. The cutter stops shearing metal from the seat under gravity alone, and this is where I stop.
You can make a wider seat if for some reason you think you have to, but it will be you to continue applying the required additional uniform pressure while spinning the cutter. If you slip up, you may go too deep and things can get difficult if you can't judge the correct force before you end up with a uniformly wider seat. If, as you try to even things out, you gouge it again in a different spot, you'll pretty soon start to feel what seems to be a 'rough' surface.
Although many feel that .005" just isn't wide enough especially compared with the seat on a full size valve, it is wide enough to seal, and the area containing the cutter scratches you can polish out for perfection is small. Once inside a running engine this pressure equalization thing starts all over again. This time the valve is beaten into the seat by the explosive forces of combustion. The area of the seat again starts to widen until the pressures are finally again equalized. However, it's now the high temperature metallurgical properties of the metal that become important in determining the final width of the seat. It's for this reason I use phosphor bronze whose properties are specified at combustion type temperatures. More commonly available (and softer) bearing bronze isn't specified for use at high temperatures although it's sometimes used. If, over time, the lash clearances continue to increase, the valve could be receding because of a wrong choice for the seat material. - Terry
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oops... I meant .005" to .007". I edited my original post. I guess people are actually reading my texts after all. Thanks. - Terry
Terry,
I think part of my problem is I used 303 or soft brass for the cages, cutter may dig in more than with your 544. This is a hit and miss engine and the plans show the valve seating on the aluminum head casting so I may be slightly better off than that.
Thanks for the help! John
I think part of my problem is I used 303 or soft brass for the cages, cutter may dig in more than with your 544. This is a hit and miss engine and the plans show the valve seating on the aluminum head casting so I may be slightly better off than that.
Thanks for the help! John
Oh believe me, we are reading your posts. I read and enjoy every single time you post and also enjoy every picture. I should probably chime in more but, don't take it as a sign that I no interest because that is far from reality. Keep up the the high quality posts. Believe me when I tell you that they are read and highly appreciated.
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Hi Terry,
For me your posts are like a great book. I just can't wait to read further to see what's going to happen! I think the running changes you're making really compliment the engine.
gbritnell
For me your posts are like a great book. I just can't wait to read further to see what's going to happen! I think the running changes you're making really compliment the engine.
gbritnell
Me too, especially these past two weeks while stuck in bed with Covid!
John W
John W
The valves were machined from 3/8" diameter 303 stainless on my little Wabeco CNC lathe without using the tailstock. For coding purposes, they were divided into five overlapping zones, each about .2 inches long. Five g-code programs, each capable of fully machining a valve inside just one of the zones were compiled and combined into a single operation. Machining began at the stem end and, with less than .2 inch stick-out, part deflection wasn't an issue. Since it wasn't necessary to reposition the workpiece in the chuck during machining, all the valve's features came out precisely concentric. A small downside to this technique was the numerous non-cutting movements at the zone boundaries more than doubled the valve's machining time. But, the 20 minute operations ran hands-off, and the long unwieldy stems came out virtually perfect.
Excess stocks of .001" were left on the stems for final polishing with 600g paper. A spare valve cage repurposed as a go-no-go gage verified the final fits while the parts were still on the lathe. The stem's upper end has to pass through its guide during assembly, but during operation there's no contact. This portion of the stem was turned three thousandths under for a later helpful clearance inside a shop-made collet. This collet was used to hold the valve for two secondary operations: 1) facing the valve's head after band sawing the valve free of the workpiece, and 2) turning the stem's lock groove.
Leak-down measurements were repeated one last time on the fully assembled valve train. Vacuums were pulled through the port liners, but stoppering the valve stem leakages with the springs installed wasn't practical. The dry stem leak-down times were on the order of 15 seconds, but with oil dropper'd on them through the springs they typically improved to 20-30 seconds. - Terry
Excess stocks of .001" were left on the stems for final polishing with 600g paper. A spare valve cage repurposed as a go-no-go gage verified the final fits while the parts were still on the lathe. The stem's upper end has to pass through its guide during assembly, but during operation there's no contact. This portion of the stem was turned three thousandths under for a later helpful clearance inside a shop-made collet. This collet was used to hold the valve for two secondary operations: 1) facing the valve's head after band sawing the valve free of the workpiece, and 2) turning the stem's lock groove.
Leak-down measurements were repeated one last time on the fully assembled valve train. Vacuums were pulled through the port liners, but stoppering the valve stem leakages with the springs installed wasn't practical. The dry stem leak-down times were on the order of 15 seconds, but with oil dropper'd on them through the springs they typically improved to 20-30 seconds. - Terry
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ajoeiam
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Hmmmmmmmmmm - - - - I 'like' the way you work!!
I'm curious about why the valves change diameter, but I love the way you did it.
I built a CNC lathe for threading back at the end of '18 and haven't used it for much. I think I want to copy your approach!
I built a CNC lathe for threading back at the end of '18 and haven't used it for much. I think I want to copy your approach!
The diameter change is the part of the stem that is in the valve cage. Reducing the stem in that area allows more room for fuel to flow into the cylinder.
Thank You. Just Thank You. Somehow I missed page 7 previously.
It made for a wonderful Sunday morning read.
I think valve seats are the biggest hurdle for the beginner .
It made for a wonderful Sunday morning read.
I think valve seats are the biggest hurdle for the beginner .
While continuing to procrastinate over the 90 degree helical gear set needed in the block for the distributor, I decided to start work on the manifolds. Since I also haven't yet decided between the stock cast iron (looking) exhaust manifold and a nostalgic (for me) tubular header, the easier to make intake manifold was tackled first.
Work began with the .020" Teflon flange gasket. Its design was derived from the manifold's CAM model and used to sanity check the protruding ports and flange mounting hole locations on the head. A 6061 workpiece was then prepared with plenty of excess stock around what would become the finished manifold. After planning its location inside the workpiece, the manifold's port passages were pre-drilled and reamed. The much longer passage connecting the runners to the carburetor mount had to be drilled through the entire seven inch workpiece. Its ends were sealed with Loctited aluminum plugs that were also pinned for good measure. The pins and plugs were blended invisibly into the manifold during its machining.
The workpiece was then moved to the Tormach where the manifold began to take shape as it was machined through the two opposite faces of the workpiece. The trough left around the semi-finished part after working through the first face was filled with Devcon 5 minute epoxy. Self-sticking (red) paper labels were used to keep the epoxy out of the exposed passages. The operations through the opposite face of the workpiece left the nearly finished manifold attached to the workpiece by only the epoxy.
The workpiece (and epoxy) at the flange end of the manifold were machined away before drilling the flange mounting holes. The engine's split manifold design requires truly flat mounting surfaces under the heads of the 2-56 SHCS's that will secure the manifold to the block. Half of these bolts pass through generous fillets left around the runners for a more realistic 'casting' look. The difficult access to these fillets required a tiny shop-made piloted counterbore to create the flats. Machined and hardened from drill rod, the tool was slotted and manually used with a screwdriver.
After completing the counterbores, the mounting flanges were finish machined, and the manifold's fit over the head's port liners could be finally verified. Remarkably, all the mounting hole locations lined up perfectly, and the snug sliding fit probably wouldn't even need the gasket. After a 275F oven bake, the epoxy released the finished manifold from the remaining workpiece.
After temporarily plugging the ports with rubber stoppers, the manifold's surface was glass beaded. Although I'm pretty sure Ford painted the original cast iron manifolds, I'll probably leave leave my 'after market' aluminum version unpainted. - Terry
Work began with the .020" Teflon flange gasket. Its design was derived from the manifold's CAM model and used to sanity check the protruding ports and flange mounting hole locations on the head. A 6061 workpiece was then prepared with plenty of excess stock around what would become the finished manifold. After planning its location inside the workpiece, the manifold's port passages were pre-drilled and reamed. The much longer passage connecting the runners to the carburetor mount had to be drilled through the entire seven inch workpiece. Its ends were sealed with Loctited aluminum plugs that were also pinned for good measure. The pins and plugs were blended invisibly into the manifold during its machining.
The workpiece was then moved to the Tormach where the manifold began to take shape as it was machined through the two opposite faces of the workpiece. The trough left around the semi-finished part after working through the first face was filled with Devcon 5 minute epoxy. Self-sticking (red) paper labels were used to keep the epoxy out of the exposed passages. The operations through the opposite face of the workpiece left the nearly finished manifold attached to the workpiece by only the epoxy.
The workpiece (and epoxy) at the flange end of the manifold were machined away before drilling the flange mounting holes. The engine's split manifold design requires truly flat mounting surfaces under the heads of the 2-56 SHCS's that will secure the manifold to the block. Half of these bolts pass through generous fillets left around the runners for a more realistic 'casting' look. The difficult access to these fillets required a tiny shop-made piloted counterbore to create the flats. Machined and hardened from drill rod, the tool was slotted and manually used with a screwdriver.
After completing the counterbores, the mounting flanges were finish machined, and the manifold's fit over the head's port liners could be finally verified. Remarkably, all the mounting hole locations lined up perfectly, and the snug sliding fit probably wouldn't even need the gasket. After a 275F oven bake, the epoxy released the finished manifold from the remaining workpiece.
After temporarily plugging the ports with rubber stoppers, the manifold's surface was glass beaded. Although I'm pretty sure Ford painted the original cast iron manifolds, I'll probably leave leave my 'after market' aluminum version unpainted. - Terry
Beautiful work, as always.
When you've got a minute, I've got to say I've never seen the use of epoxy like you're doing here. What does that do? Does it add strength to help it resist the machining forces from the other side, or is it cosmetic?
When you've got a minute, I've got to say I've never seen the use of epoxy like you're doing here. What does that do? Does it add strength to help it resist the machining forces from the other side, or is it cosmetic?
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I've leaned this from Terry; allows all the surrounding bottom stock to milled away while holding the finished part, which would otherwise remain unsupported. Then the part is released by heating,
Bob,
It's just like kvom said. The Devcon keeps the already machined side of the part connected to the workpiece so the other side can also be machined free of it while still being held in place. A strong epoxy is needed, but also one that gives up at a reasonable temperature. JB Weld continues to hold on at temperatures that are too high to be useful and isn't useful in this application. Devcon 5 minute epoxy used to give up at a much lower temperature, and I could get it to release with a heat gun. I think they changed their recipe a few years ago, and now an oven bake is needed. I may try one of the high temp glue sticks. The low temp stuff might melt under the heat of some machining operations without sufficient coolant. - Terry
Thanks Terry and kvom. I didn't have a good mental picture of what was being cut away and what would happen to it. I see you're cutting away all the aluminum holding those branches of manifold in place and I can imagine those pieces moving enough to get some irregular marks on the pieces. Or worse.
