1/3 Scale Ford 289 Hi-Po

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Great work as usual Terry. You might have mentioned in the past - but how do you cut your gaskets?
Dave,
Thanks. I have a vinyl cutting tool installed in a drill chuck on my Tormach. It's basically A carbide knife that rotates on a pair of bearings as it's laterally moved around. - Terry
 
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.
Amazing work as always! So you use a 4 flute cutter on aluminum. I use a 2 flute 1/16" cutter when I really need detail machining, but do break them now and then, especially if I try anything like a .030" DOC. I thought a 4 flute would plug easier when cutting aluminum. I do use a mist system. Maybe my cutters aren't the best quality.

Rick
 
There was also an after-market Cobra oil pan available for some of these engines, but in my opinion it was a little gaudy, and so I aimed for a reasonable facsimile of the stock drawn-steel pan.

As tradition, construction began with a cut-off from my stick of 7075 that I turned into a nine pound workpiece. Something I didn't mention earlier is the difficulty I've been having with band-sawing large chunks of this particular (T73511 heat treat) alloy. I have a typical imported horizontal bandsaw with pneumatic down-feed that's been cutting 6061 and various steels flawlessly for the last twenty-five years. However, it doesn't seem capable of accurately cutting thick sections of this stuff. I've tried readjusting the blade guides, but the kerf invariably drifts outward nearly half an inch in a three inch deep cut. On one occasion the tension increase broke a bimetal blade.

The first machining operation was to drill the holes in the bottom of the workpiece for the pan's mounting screws. The front face of the pan was then fully machined while the tall workpiece was clamped on end in a vise. After repositioning, the rest of its exterior was machined. That pesky sloping underside which is similar to the original pan created a lot of finish machining. The three inch cutter stick-out needed for these operations demanded large diameter cutters - not only for chatter control but for reasonable material removal rates. If I could have trusted my bandsaw I'd have sawed away most of the waste from the workpiece before starting.

I searched my eBay drawer for re-sharps or any odd cutter that might speed things up. I found a 7/8" HSS ball cutter that should have been useful for finishing, but it was intended for a Weldon tool holder which I didn't have. It chattered uncomfortably, and after an hour it slipped in my R8 collet. Before I could react, there was a deep gouge across the bottom of the pan. The time I'd hoped to save using that big cutter was spent filing out the gouge and re-contouring the bottom of the pan. In the end, 90% of the workpiece was turned into chips with 1/2" cutters that required some fifteen hours. A few hours would have been saved by not finishing the interior, but since I'll be looking at this thing for the next several months the extra time isn't important.

The model's large size only became apparent when I held the finished oil pan in my hands. Its massive half liter sump capacity is overkill, and so the interior really didn't need to be milled to its full depth. In addition to a drain plug, provision was made for a fill plug higher up on the rear of the pan. The oil fill plug is Plan B in case filling through the dipstick tube isn't practical. The floor of the pan was also counterbored for a magnet that was epoxied in front of the drain hole. A set of pan gaskets were cut from .020" Teflon.

After bead blasting, the pan was Gun-Kote'd with a color near to Ford Blue. While my makeshift cardboard paint booth was still set up, the intake manifold and timing cover were Kote'd as well.

Two major casting remain - those for the water pump and bell housing. The bell housing still needs a lot of thought and some testing since I'm still keen on a realistic electric starter. Family is coming in for a week, and then it will be on to the water pump. - Terry

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However, it doesn't seem capable of accurately cutting thick sections of this stuff. I've tried readjusting the blade guides, but the kerf invariably drifts outward nearly half an inch in a three inch deep cut. On one occasion the tension increase broke a bimetal blade.
Are you using a course enough blade? I have a chunk of 3" thick aluminum of unknown grade that I had trouble cutting; blade drifting a lot. I switched to a course tooth blade (can't remember off hand, but maybe 6-8 tooth) and the cuts were dead straight after that.
 
Hi Terry
Is there a reason you use 7075 instead of 6061. I realise it is a stronger alloy but was wondering what was the advantage on an item such an oil pan.
Thank you
 
I use ten teeth/inch as a compromise blade for aluminum and steel since I regularly cut both and don't want to keep swapping blades. Except for this stuff I've never (and still don't) have trouble cutting 6061.

I'm using 7075 because I had a huge piece of it purchased many years ago for next to nothing. I like to use scrap material for my models whenever I can, but the recycler I used to buy from no longer sells to the public, and I had no pieces of 6061 sitting around that were big enough for this project.

On the upside, the surface finishes you can obtain with 7075 are beautiful, but you have to be very careful when drilling and tapping small holes. Fortunately, I've gotten away with only a few 0-80's and 1-72's so far. I use only carbide tooling, and I suspect the chatter fiasco with that 7/8" HSS cutter had something to do with the 7075. - Terry
 
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Wonderful work Terry! Forgive me if I missed it in previous posts (I get sidetracked pretty easily with all your great pix..), but how are you tapping the holes in all that aluminum? Have you tried form taps? What are you using for cutting fluid? Are you just using the recommended drill sizes from the charts or are you using different sizes?

I got a message from a friend tonight who picked up an old Jeep (Willys) his father owned that has a 289 in it, it's going to be a BIG project, but pretty exciting, it'll be the 3rd or 4th 289 I'll have wrenched on/rebuilt. I'm pretty excited about that, they're a fantastic little engine. Maybe I can talk him into the Cobra valve covers & air cleaner. I don't know if I can sell my friend on the Weiand carbs like George modeled up, but boy, that would be nice.

John
 
Wonderful work Terry! Forgive me if I missed it in previous posts (I get sidetracked pretty easily with all your great pix..), but how are you tapping the holes in all that aluminum? Have you tried form taps? What are you using for cutting fluid? Are you just using the recommended drill sizes from the charts or are you using different sizes?

I got a message from a friend tonight who picked up an old Jeep (Willys) his father owned that has a 289 in it, it's going to be a BIG project, but pretty exciting, it'll be the 3rd or 4th 289 I'll have wrenched on/rebuilt. I'm pretty excited about that, they're a fantastic little engine. Maybe I can talk him into the Cobra valve covers & air cleaner. I don't know if I can sell my friend on the Weiand carbs like George modeled up, but boy, that would be nice.

John
I tap the holes manually using a shop-made tap block - nothing complicated, just a block of Delrin with a hole drilled in it for the tap shank. I use WD-40 for tap fluid and the chart recommended 75% engagement tap drills. Gun taps for through-holes, and tapered followed by bottoming taps for blind holes. - Good luck on your full-size build. - Terry
 
I tap the holes manually using a shop-made tap block - nothing complicated, just a block of Delrin with a hole drilled in it for the tap shank. I use WD-40 for tap fluid and the chart recommended 75% engagement tap drills. Gun taps for through-holes, and tapered followed by bottoming taps for blind holes. - Good luck on your full-size build. - Terry
In 7075 and 2½ diameters engagement you can likely get away with a 65% thread, yield and tensile strength are almost as high as 1018 steel.
 
That's some tenacity there. Very nice!

Have you tried corncob mills or the newer variable indexed flute mills? They vary the helix indexing to reduce chatter when hogging out aluminum. I hear they work pretty good on thin-walled parts too.
 
That's some tenacity there. Very nice!

Have you tried corncob mills or the newer variable indexed flute mills? They vary the helix indexing to reduce chatter when hogging out aluminum. I hear they work pretty good on thin-walled parts too.
I once tried a corncob mill and I seem to remember having good success with it. I have one variable pitch cutter but its only 3/8". I may revisit a corncob cutter when its time to machine the bell housing. - Terry
 
Several water pump variations were used on the small block Ford: forward vs. reverse flow, driver or passenger side inlet tube, and with or without a back plate. Although less common, I chose the driver-side inlet to avoid crowding the area around the alternator on the passenger side. I also decided upon a backing plate to improve my chances of a sealant-free seal between the pump and timing cover. However, this required machining away the mounting flange on the front face of my already finished and painted timing cover.

Pump construction began with the backing plate. The plate was machined from .030" aluminum sheet, and the clearance holes for the snug-fitting water tubes on either side of the pump left minimal slivers of metal around them. I didn't want to invest time into machining the pump body until I had a usable back plate in my hands.

A piece of unknown (and no doubt gummy alloy) aluminum sheet was super-glued to a sacrificial block, and the backing plate was machined using a two flute .093" end mill (5 krpm, 3 ipm, .020" d.o.c.) with plenty of coolant. The part was released using heat and cleaned up with acetone. The whole process went better than expected, but for insurance I made a spare. To ensure a close fit inside the the pump body, the same end mill was used later when machining the plate's mounting recess in the rear face of the pump body.

The workpiece for the pump body was created by squaring up a cut-off from my favorite stick of 7075. I finally figured out the issue I'd been having with my bandsaw. The problem with the skewed cuts was evidently simply too much down feed rate - an embarrassing rookie mistake.

The bore for the impeller assembly was manually drilled/reamed and then used to reference the machining setups for the rest of the pump. The pump's rear face was machined first. The backing plate's snug fit was achieved by repeating its machining operation and declaring its diameter to the CAM software a thou less each time until the backing plate literally snapped into place.

The rear of the pump was finish machined down to half the pump's thickness. The trough left around it inside the workpiece was filled with Devcon 5 minute epoxy and allowed to cure overnight. The epoxy held the pump securely within the framework of the workpiece while the front half of the pump was also finished down to half the pump's thickness. In a third operation a corner of the workpiece was cut away, and the opening for the hose pipe was drilled through and reamed with the workpiece clamped upright in a vise. The finished part cleanly released from the workpiece carcass after a 350F oven bake. After bead blasting the pump was Gun Kote'd Ford blue, and the timing cover was re-painted.

The parts for the impeller assembly will be machined next, and the assembled pump will be leak checked and flow tested using a couple different impeller designs. - Terry

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After posting the above photo I realized I forgot to show the backing plate between the impeller and the pump gasket.

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