1/3 Scale Ford 289 Hi-Po

[mayhugh1]

Continuing on with the rods ...

The bores for the small end bearings were drilled and reamed next. The bearings themselves were turned from 932 bronze and preinstalled in the workpieces where they would later be blended into the rods during their machining. I considered it a good sign that their fits augmented with Loctite 620 set up almost immediately. After several hours at room temperature they received a final one hour cure at 190F.
The openings on the big ends were manually drilled and finished with a boring head. I expected the .675" pilot holes to be tough-going since 7075 seems to drill like steel. Rather than come up with feeds and speeds for the Tormach, I decided instead to wrestle with the quill and wrench my shoulder.

The workpieces were moved to the Tormach where the real machining took place. Since the workpieces were identical they could be fed into an end-stopped vise without the need to re-indicate each part. The roughing passes used 1/4" and 1/16" end mills and left .005" excess material around each part for finishing. An 1/8" ball mill was used in the finishing passes. Witness numbers engraved on either side of the rods' parting lines will keep the halves from being mixed up later.

The troughs (those things Charles doesn't like :>)) left around the semi-finished parts during their topside machining were filled with Devcon 5 Minute epoxy and allowed to cure overnight. Silicone plugs shielded the rod bolts from the epoxy.

The setup used to machine the bottom faces was a mirror image of the one used to machine the top faces. Flipping the workpieces over this way allowed the same corner in both setups to be used as a machining reference and minimized registration errors. The bottom face machining operations were essentially identical to those on the top face. Total machining time for each pair of rods was about three hours.

I made a last minute change to the depths of cut of the finishing passes on both faces to create a forged seam line around the periphery of the rods for a little more realism. While doing so, I wasn't paying attention to what I was doing to the final epoxy thickness. I typically design for 3/16" and was alarmed when the parts began coming out with as little as .020" and in a few places broke through entirely. Even so the the parts seemed to be rigidly attached to their frameworks and I continued on. I was lucky a couple didn't dislodge and become damaged. The final operation was to swap out the rod bolts for some with shortened heads so the temporary bolt covers could be machined away. This operation was moved to the manual mill where I could keep a close eye on things.

An oven bake at 275F released the parts from their workpieces, and then they were bead blasted. Still left to machine are the big end's split bearings and some oil passages before fitting them to the crankshaft. - Terry

 

[GreenTwin]

Dang that is beautiful work !

.

 

[mayhugh1]

Split bearings in a pressurized oil system, especially those with oil grooves, need a full 360 degrees of coverage around their journals to avoid leaks and pressure loss. In a splash lubricated system, full coverage isn't necessary and may not be desirable. Shop-made model bearings designed for something less than 360 degrees can be easily and efficiently machined.

Bearing construction started by turning the o.d.'s of a couple 932 bronze drops to a couple tenths under the i.d.'s of the big ends. The i.d.'s were then bored a thousandth over the journal o.d.'s before parting off the individual bearings. A simple fixture held the bearings while they were being sawed in half with a .016" thick slitting saw. The metal lost by the saw's kerf reduced the bearing's coverage by about six degrees.

Full size automotive bearings have a tang which engages a recess in the rod to keep the bearing from spinning inside the rod. Instead of tangs or pins, I elected to permanently bond the bearing halves inside the rods with Loctite 638. If the bearings are exactly on dimension they will 'snap' in place when pushed into the rod halves. Only about half of my bearings fit this well, but then that's what the Loctite was for. Spacers machined from Delrin were used to temporarily hold the bearings tightly against the rods while the Loctite cured.

Machining was wrapped up with the drilling of a pair of oil ports through the rods' shoulders to help with big end lubrication. A similar pair of holes was drilled in the little ends of the rods. All four holes were drilled with the rods in a simple fixture and the Delrin spacers still in place.

A couple rods were installed on the the crankshaft inside the block to verify clearances with the bottoms of the cylinder liners which stick out a little inside the block. While designing the rods I'd been too focused on the clearances between the liners and the rod bolt heads and completely missed an interference problem further down the body of the rod. Sure enough, my assembly model knew about the problem but didn't text me with a warning. It's only a couple thousandths and could be fixed with a file, but I'll likely set the block up in the mill and do it right. I generally like .020" to .030" clearances around the rods. - Terry

 

[peterl95124]

Nice !!!, so far all my IC engine big ends are lubed by pressure through passages drilled in the crankshaft, but if/when I use a splash system this here is what I'll base it on !!!

 

[mayhugh1]

Fixing the rub ...

The bottom ends of the liners which stand .040" proud of the block created a couple thousandths interference with the sides of the rods that went unnoticed in the live assembly model. With the block stripped down and set back up in the mill, a quarter inch wide strip was removed from each liner. A couple magnets wrapped in a paper towel and stuffed inside the liner being worked kept the chips under control.

Thanksgiving, so much flu, but finally some pistons ...

The piston work started by band sawing five 1-1/4" diameter 6061 workpieces. Each was long enough for a piston on either end and a work-holding spigot in the center. The ends were turned down to the finished o.d.'s of the pistons which are two thou under the liner i.d.'s. The top eighth inch of each piston was turned down an additional two thou to accommodate thermal expansion. With the ends of the workpieces at their finished diameters, the ring grooves were cut.

The pistons were designed with two compression rings and an oil groove immediately below the bottom ring. Oil scraped from the cylinder wall on the downstroke will fill the oil groove and be directed inside the piston through a series of radially drilled holes. Oil control comes from less oil having to be pushed along the entire stroke.

The .027" ring groove widths were arrived at using Trimble's equations for cast iron rings, (and the fact that I had a .027" grooving insert). The depths of the grooves include .006" clearance behind each ring. The semi-finished pistons were then parted off their workpieces. The oil holes should have been drilled before parting off the pistons, but with the vise still needed for a while, I put off swapping it out for the back-breaking rotary.

A fixture was created to hold the pistons in the mill vise for additional machining. With the fixture stood on its side, the wrist pin holes were drilled and reamed. It was important for these holes to be perpendicular to the pistons' axes (my max allowed error was 0.1 degree) in order to prevent excessive wear on the rod bearings. The flats straddling the wrist pin bores and the oil holes directly above them were machined in a second setup.

With the help of the fixture, the pistons' internal features were machined on the Tormach. The very first part went badly due to an error in the work zone definition provided to the CAM software. The mill began eating the fixture when it tried to re-machine the o.d. of the piston. The program was halted before the fixture was damaged beyond use, but one of my spare pistons was trashed in the process. After regenerating the code, the bottom end machining was completed on the remaining nine pistons.

The final step was to automate the drilling of nearly 100 oil escape holes. Not only were the individual pistons difficult to hold, but getting a tiny drill up close and personal to them was another problem. Eventually, a suitable fixture was fashioned from an emergency collet.
The wrist pins wrapped up the piston-related work. I've used the same floating pin design on nearly all my engines. A pair of hemispherical aluminum rivets were pressed into the ends of the 5/16" polished drill rod lengths used as the pins. The pins' sliding fits ease assembly, and the wrist pins self center while running. The soft rivets protect the liners. Oil entering the escape hole directly above each wrist pin provides lubrication through an internal passage.

The pistons and rods were installed in the block for safe keeping where they'll remain until the rings are machined. The next steps include finalizing the design of the valve train so work can begin on the camshaft. - Terry

 

[mayhugh1]

More Photos ...

 

[Basil]

Interesting design with the piston oil return. My Seal Major smokes more than I would like and this could be an easy solution without having to make another ring. Have you used this idea before? Thank you Terry, I'm learning lots.

 

[mayhugh1]

Interesting design with the piston oil return. My Seal Major smokes more than I would like and this could be an easy solution without having to make another ring. Have you used this idea before? Thank you Terry, I'm learning lots.

Yes, I've used this on four of my engines and have been happy with the results. I didn't invent it - just offering an explanation of how it works. Terry

 

[mayhugh1]

Work started on the valve train, and with a couple hundred parts ahead of me I'll be a while. The valves' 5/16" diameter was locked in by the already machined heads. The intakes could have been bigger, but with the engine's huge plenum and long runners I was concerned about flow and manifold vacuum and decided to trade a tall top-end for a healthy low speed idle. At this point the valve train had only been modeled using crude placeholders.

The holes for the rocker studs and valve cages were also drilled during the heads' machining since I expected to be able to come up with a combination of springs, rockers, and lobe heights that would work with the existing pushrod angles. When it came time to design the actual parts, I discovered the design had been locked into a rocker ratio of two which would have forced the lobe heights to be much smaller than I wanted.

Although the full-size engine's rocker ratio was 1.6, a more suitable ratio for the model worked out to be closer to 1.3. With the rocker studs sitting between a pair of internal coolant passages and minimal clearances around them, altering their locations at this point was scary. However I managed to reach a 1.3 ratio with an angle change of the rocker studs in addition to a small lateral movement. Upsizing the studs from 6-32 to 8-32 covered up nearly all traces of the earlier holes.

The rocker arm design was tackled first. I wanted it to have the look of an old school forged rocker, but I also needed a roller since the top-end won't receive lots of lubrication. A pair of first article rockers were machined from 7075 along with the shafts, rollers, mounting studs, adjusters, springs, and retainers needed to test them. A couple dummy pushrods and lifters were also made up.

A simple shop-made fixture temporarily inserted into the valve cage bores allowed me to check the location of the roller tip with respect to the valve stem. The stud relocation evidently came with some errors causing the roller to be slightly off center of the valve. The rear of the rocker was also uncomfortably close to the rocker cover. These were corrected in a second iteration.

The fixture was also revised to include a loaded valve spring captured on a threaded dummy valve stem that allowed the rockers to be exercised and the seat pressure measured. The valve stem height was also established.

A final prototype of each component making up a rocker assembly was machined and retested before going into production to be very sure there'll be no more re-work. - Terry

 

[TonyM]

Lovely work. My only concern/question is regards the gap in the big end shells. I have never seen or made shells which are not complete halves which is more difficult and wasteful. Have you had success before with just splitting rounds and leaving the gap?

 

[mayhugh1]

Lovely work. My only concern/question is regards the gap in the big end shells. I have never seen or made shells which are not complete halves which is more difficult and wasteful. Have you had success before with just splitting rounds and leaving the gap?

Tony,
Yes, I've done it twice before. I really don't think it's a problem in a model, especially one that's using splash lubrication. But, we'll see. The question you should be asking is if an oil pump is really needed.

If you could look through the oil pan of a running engine you'd wonder why even a full size engine needs an oil pump since every surface in the bottom end would be covered in oil from the maelstrom whipped up in the sump by the rotating parts. It's so bad that many engines have windage trays to keep this whipped up oil from robbing horsepower. The reason for an oil pump is to keep a pressurized oil film in the bearings so the high forces created when delivering power don't push the parts on either side of this film together so hard that the film is penetrated and metal-to-metal contact is created. In this case full coverage bearings are needed to ensure the high pressure oil doesn't escape through the leaks they would create which in turn would starve the downstream bearings. In a running model that isn't doing much work and not delivering power, these forces aren't high enough to be a concern. We typically put oil pumps in model engines just because we can and because we want the models to look like the full size engines we're trying to emulate. Look at all the examples of Steve Huck's Demon engine that are out there running without an oil pump. He must have a hundred hours running time on the one he takes to shows. Same goes for George Britnell's inline six. - Terry

 

[mayhugh1]

So many little parts ...

One last revision of the rocker arms was prototyped before machining them en masse. They were then machined in batches of five with each from its own little 7075 workpiece. Small batches aren't very efficient, but they allowed fine tuning of the process without the risk of a systematic error that might scrap the whole lot.

After band sawing the workpieces from remnants of my 7075 stick, the initial operations trued up their sides and manually drilled and reamed holes for the rollers and rocker shafts. The workpieces were then moved to the Tormach where the rockers' profiles were machined. Their tops and bottoms were roughed with an 1/8" cylindrical end mill and finished with a 3/32" ball cutter. Tormach's spindle Speeder running at 14 krpm brought the ridiculously long machining times down to a reasonable 30 minutes per side. Parts changes in the vise were quicker to make than tool changes in the Speeder, and so roughing passes were completed on all parts in each batch before going on to the finishing passes.

I used all the tricks I knew to speed up parts changes including a vise stop and a pair of springs between the parallels to reduce chip cleanup time. Total fab time per batch of five rockers including their workpiece preparation was about six hours, and so the four batches required a full 24 hours of machining time. The rockers were bead blasted and will later be burnished with Birchwood Casey Aluminum Black to look like distressed forged steel.

The rocker studs were machined next. These were made up of a lathe-turned center body and a pair of threaded studs. After machining the body from 12L14 hex rod, both ends were tapped for screws which were threaded through shop-made filing buttons before being Loctite'd in the body. Once the heads were sawed off, the buttons were used to file the screws down to their finished lengths, and then the buttons removed. The completed rocker studs were cold blued to protect the 12L14 from rust.

The adjusters were also machined from 12L14 hex rod. Each was tapped-through for threading onto the rocker studs. Grub screws in their top-ends will eventually lock the adjusters in place once lash is adjusted. The adjusters were also cold blued.

The rocker shafts were machined from polished drill rod. The arms rotate on these shafts which are inserted onto the rocker studs. The adjuster which rests against a milled flat on the top side of the rocker shaft captures the arm between the adjuster and the tops of valve stems and the pushrods where it's free to rotate.

The tip rollers and their shafts were also machined from polished drill rod. These simple parts required a surprising number of lathe operations, and being hard to support put them in the PITA category. Other PITA parts included the upper spring cups which were machined from 303 stainless. A 5C collet stop helped with one of the two counterboring operations. The installed spring height will be set by a 2.5 mm e-clip inserted into a groove on the tip of the valve stem and resting in this counterbore.

The springs were wound with five turns of .024" music wire over a .230" mandrel. Their o.d.'s are .300", and their free height is .600". The measured spring rate was 4.8 lbs/in. At their installed height the measured seat force will be about 1.25 lbs. The formed springs were normalized at 400F for three hours and then tumbled in walnut shells. They'll be Gun-Kote'd later.

I've been wanting to design a roller camshaft, and my plan all along has been to put one in this engine especially if its top-end oiling system is limited (still haven't decided on whether there will be an oil pump). I'll next see if I can come up with strapped lifter pairs that will work with my block and heads. - Terry

 

[Ghosty]

Terry,
Merry Christmas and Happy New Year to you and yours from Me and mine.
Great work as usual, the rocker arms almost look cast in the pics.
Can't wait until it is up and running.
Cheers
Andrew

 

[petertha]

Very nice, Terry. Maybe I missed it but are either the roller or shaft hardened? What retains the shaft within the rocker finger holes? About how much valve lift will you have?

 

[mayhugh1]

Very nice, Terry. Maybe I missed it but are either the roller or shaft hardened? What retains the shaft within the rocker finger holes? About how much valve lift will you have?

The shaft will be pressed into place, and right now I'm not planning to harden either. The max lift will be .100". - Terry

 

[oldCB]

Outstanding craftsmanship Mayhugh. I'm blown away.......

 

[mayhugh1]

Although I hadn't yet gotten to the valves and valve cages, I needed a break from the mind-numbing valve train parts production. To ease the monotony, I prototyped a pair of roller lifters to see if a roller camshaft could be made to work in this engine. Of course the lifters gained some components, and the list of valve train parts got even longer.

The main advantage of a roller cam is the steep opening ramps that are possible. These can allow the cylinders to be more completely filled and evacuated without the need to increase cam duration. Steep closing ramps are a source of valve bounce, and the lobes on a roller cam are sometimes asymmetrical. Roller cams also reduce friction in an engine which can be very desirable in a model.

An important consideration in the design of a roller cam is maintaining alignment of the axes of the rollers to that of the camshaft. Strapped lifter pairs are typically used. A difference among manufacturers is whether the rollers contain needle bearings or bushings. There's some anecdotal evidence that suggests needle bearings hold up better than bushings when a roller cam is installed in an engine with an oiling system designed for flat tappets. It's interesting that the cam/roller contact in retrofits typically relies upon splash lubrication even though the engine has a windage tray.

The rollers in my design are tiny ball bearings, but they aren't your typical slot car bearings. I've been waiting for just the right application to use some of the high-rel bearings purchased from an industrial surplus outlet years ago. They're fully sealed 440C stainless steel units with a convenient raised shoulder on either side of the inner race and supposedly rated for an incredible 60k rpm.

The roller considerably complicated the lifter body design and added a dozen lathe and milling operations to its fabrication and extended the machining time of each to just under two hours. The lifter bodies and shoulder bolts were machined from drill rod but left unhardened. The connecting straps were hardened and so will the pushrods when they're machined.

In order to test the roller setup, a pair of cam lobes were roughed into the test rod I've been using as a dummy camshaft. The camshaft's design hasn't yet been finalized, and so the lobe pair used was taken from the solid tappet placeholder in my SolidWorks assembly model. Its linear ramped lobes have 260 degrees of duration and a lobe separation angle of 112 degrees.

The prototyped roller pair was installed in the block and run against the dummy lobe pair for operational and clearance checks. This was an important step because although I wasn't expecting problems, roller cam hardware is new to me, and if a problem should show up later during final assembly it could scrap a lot of parts that would be miserable to re-machine. The lift, rocker arm ratio, and final seated spring force were verified and the final pushrod length determined. With the lifter hardware finalized I went back into production mode and machined the some 70 parts (including spares) associated with it. The pushrods will be machined later once the finished camshaft is in hand since they will offer my last opportunity to make minor tweaks to the valve train.

The next step is to machine the camshaft whose design has been giving me fits. The interleaved lobes resulting from the offset 90 degree heads add a mind-twisting complication for someone who has never before machined a Ford V-8 camshaft from scratch. Before making chips, I had been trying to compare my model to online photos of early Ford camshafts. I had to combine several photos to create a composite showing all the lobes. As luck would have had it, one of these photos was of a camshaft with an alternate firing order (I wasn't even aware that there were two small block Ford firing orders), and another photo evidently contained a reversed marine camshaft. After a frustrating week, George Britnell was kind enough to send me a drawing that allowed me to sort all this out. - Terry

 

[petertha]

I've been waiting for just the right application to use some of the high-rel bearings purchased from an industrial surplus outlet years ago. They're fully sealed 440C stainless steel units with a convenient raised shoulder on either side of the inner race and supposedly rated for an incredible 60k rpm.

This is very timely. I was looking at putting bearings into rocker arms of my next build but was starting to get fussed about shim washers between the inner race & vertical cage & spacer tube between bearings. Does 'high-rel' (=relief? =reliability?) always infer this raised shoulder feature or does one look for its presence specifically? What is the size of your bearings.

 

[mayhugh1]

This is very timely. I was looking at putting bearings into rocker arms of my next build but was starting to get fussed about shim washers between the inner race & vertical cage & spacer tube between bearings. Does 'high-rel' (=relief? =reliability?) always infer this raised shoulder feature or does one look for its presence specifically? What is the size of your bearings.

Petertha
I used the term hi-rel to mean high reliability. The bearings are .250" dia and .223" wide including the shoulders. I've never before seen bearings with these raised shoulders, and that was one of the reasons why I bought them.

They were a one-off lot purchased from the CDD Surplus Store in Richardson, Texas. - Terry

 

[oldCB]

Blown away Mayhugh.......beautiful work.