Ford 300 Inline Six

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mayhugh1

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The tappets in Ford's inline six are accessed through a recess cast into the starboard side of the block just above the camshaft. They're located behind a tappet cover that fully encloses them and is hopefully leakproof. Simulated stiffeners on the cover's outside surface are a nice cosmetic touch, and the rear face has a sealing lip around its periphery.

Machining began with the cosmetic detail on the cover's outside face. This was machined into the top surface of a .185" thick aluminum workpiece while clamped in the vise on tall parallels. After band sawing the semi-finished cover free, it was flipped over and temporarily glued to a piece of MDF using a quick setting Devcon Epoxy Gel. The workpiece was indicated with the MDF clamped in the vise while the epoxy cured. After all the machining was finished, the part was released with a half hour bake in a 300F oven.

There's a possibility of interference between the cover and the distributor, and so the lower edge of the cover was relieved just above the distributor's mounting boss. This may have to be revisited after the distributor is machined and its bore in the case is finally drilled.

The cosmetic detail on the front face of the timing cover is another nice touch. Changes were required to the timing cover to accommodate earlier modifications made to the front ends of the block and oil pan for the front ballbearing. Hopefully, oil will find its way into the timing gears through a small hole drilled between them through the front of the block. The front pulley's hub will be grooved for a rotating 0-ring seal to prevent oil from leaking around the shaft. Both covers were bead blasted in preparation for painting. - Terry

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Basil

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Hi Terry, On the timing cover are you gluing the aluminum to the MDF and holding the MDF in the vice for the full operation?
Cheers
Mike
 

mayhugh1

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Hi Terry, On the timing cover are you gluing the aluminum to the MDF and holding the MDF in the vice for the full operation?
Cheers
Mike
Mike,
Yes, the workpiece was on the MDF for the entire machining of the cover since the rear face was flat and didn't have to be machined. - Terry
 
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mayhugh1

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It's not a good idea to finish all the fun stuff at the front end of a long build, so I decided to work on the mundane cylinder liners. After lapping, they'll be installed in the block with .004" (diameter) slip fits and sealed with Loctite. When machining the water jackets earlier, generous top and bottom sealing rings were left behind for Loctite, and hopefully coolant leaks won't be an issue.

The first step in construction was to machine a Delrin plug gage that was trial-fitted in each cylinder location to verify the liners' dimensions. With those dimensions in hand, eight 2" long starting blanks were band-sawed from a 1" diameter Stressproof rod. Each workpiece included a 3/4" holding spigot. One of the two extra cylinders will be completely finished and used later for the piston ring light tests.

The liners' 3/4" bores were initially opened up to about .65" with two drilling operations. Their o.d.'s including the top sealing lips were then turned and finished. A grooving tool turned a sharp inside corner and a slight undercut immediately below the lip. Stressproof is a joy to turn with its beautiful surface finishes so easily obtained with little effort.

However, boring Stressproof is an entirely different matter. Its 2X hardness demands a very rigid boring bar setup for acceptable results. I was finally able to get nice surface finishes using a 1/2" bar with a 1.5" stick-out and high rake CCGT inserts designed for aluminum. Chip evacuation was a major problem however. The boring had to be split into three separate operations with the workpiece being removed after each so chips could be unpacked from both the workpiece and collet.

A final operation using a fresh insert removed the last .020" from each bore. Since the piston rings aren't yet machined, the exact bore diameter wasn't important. In order to minimize the lapping effort, however, I was keen on starting out with all the bores nicely finished and as close as possible to an identical diameter.

After parting off the tooling spigots, the parts were marked with unique numbers in preparation for lapping. A worksheet containing a running history of the top and bottom bore measurements was set up so the lapping progress could be tracked for each liner. Although the starting diameters were within a thousandth of one another, each liner had a slight taper running in the wrong direction.

An Acro barrel lap and 280g Cloverleaf grinding grease was used for all but the final lapping steps. The final pass used 600g grease and removed a negligible amount of metal. A silicone pipe cap was slit open and wrapped around each liner so it could be safely gripped in one hand while the lap was spun by a battery powered drill in my other hand. Drill speed was 200-300 rpm while the part was oscillated over the lap at about 1 Hz.

Bore measurements were made using an inexpensive dial bore gage that had a repeatable resolution on the order of a tenth. After zeroing the gage on an arbitrarily selected liner, plus/minus deviations were recorded after each minute or so of lapping. The liners were thoroughly cleaned with kerosene (the smelly part of the messy process) before being measured.

The tapers were slowly removed by dwelling in the tight end of each liner. After the tapers were removed, all seven liners were carefully brought to the same diameter within the measurement resolution of the gage. Total lapping time worked out to be about four hours with about a thousandth removed from each liner.

The liners were installed with Loctite 620 and the block assembly set aside to cure overnight in my 130F welding rod oven. After an additional 24 hours, the excess uncured adhesive was washed off the liners' exterior walls by pumping solvent into the drilled inlet for the water pump with a syringe.

Before finally facing the deck, I looked at my options for compression ratio. The combustion chamber's shape is fairly complex, but SolidWorks was able to compute its volume. Modeling showed the compression ratio to be 5.7 with no head gasket and 5.4 with a .010" head gasket. I plan to use a .020" head gasket and would like to wind up with a c.r. closer to seven, and so I'll likely increase the heights of the pistons as needed. - Terry


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Willyb

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Hi Terry
Wanted to say that I'm very impressed with your project and your attention to detail is just amazing. Thank you for allowing us to follow along with your progress of this project. Thanks again
Willy
 

petertha

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A Diacro barrel lap and 280g Cloverleaf grinding grease was used....
Is this just a typo and you mean Acro brand lap?

Re the insert, I've noticed the exact same thing about my CCMTs - sometimes my uncoated 'for aluminum' inserts cut with more uniform surface finish & seem to hold DOC better. They are also Korloy (or so says the Ebay/AliExpress label). I wasn't quite sure if it was absence of typical gold coating for steel alloy or sharper nose radius or maybe rake related to boring specifically. The uncoated don't seem to degrade noticeably faster but are a bit more prone to chipping if you push them as would be expected. I recently bought some 'for stainless' inserts with black coating & selected a smaller radius than normal. I'll get the specs if you are interested. They seem to behave nice on stainless from what I recall making my valves. But now I will give it a go on 1144SP. Part of the mystery is you never really know what you're getting (at least the dark alleys I've been shopping). And probably machine & tool rigidity factors too.
 

mayhugh1

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Is this just a typo and you mean Acro brand lap?

Re the insert, I've noticed the exact same thing about my CCMTs - sometimes my uncoated 'for aluminum' inserts cut with more uniform surface finish & seem to hold DOC better. They are also Korloy (or so says the Ebay/AliExpress label). I wasn't quite sure if it was absence of typical gold coating for steel alloy or sharper nose radius or maybe rake related to boring specifically. The uncoated don't seem to degrade noticeably faster but are a bit more prone to chipping if you push them as would be expected. I recently bought some 'for stainless' inserts with black coating & selected a smaller radius than normal. I'll get the specs if you are interested. They seem to behave nice on stainless from what I recall making my valves. But now I will give it a go on 1144SP. Part of the mystery is you never really know what you're getting (at least the dark alleys I've been shopping). And probably machine & tool rigidity factors too.
Thanks, you're right. I've corrected it to Acro.
Those high rake Korloy inserts produce beautiful surface finishes, but they wear quickly on ferrous metals. When I absolutely need to use them on stainless or a tough steel, I'll save the dulled carcass for a later aluminum roughing operation. - Terry
 

mayhugh1

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A lot of full-size detail was included on the model's head making it an interesting mini-project of its own. For completeness, George even designed his own 8-40 threaded spark plugs. Fouling became an ongoing issue however, and he recommended I try something larger. I had good results with the Viper VR-1's in my Merlin, and the changes required to fit them in this head were relatively minor. Turning down the end of a 6 mm socket for use as an installation tool minimized the necessary modifications, but the plug depths inside the combustion chambers did have to be corrected.

George machined his head from cast iron and used integral valve seats. Cutting seats directly into a head after it's accumulated tens of hours of machining time seemed too risky to me. Since I also don't like machining cast iron, I elected to use 7075 aluminum and to install pre-tested bronze valve cages.

Machining began with the outside perimeter of the head as well as the drilling and reaming of the numerous holes through its bottom surface. Three coolant passages also run lengthwise through the head and were drilled using Gurling deep hole drills. These small passages were machined by drilling half-way through each end of the workpiece.

The model's coolant system is very similar to the one in the full-size engine. The water pump drives coolant into the front of the block so it can flow sequentially through the water jackets surrounding the cylinders. At the rear of the block, it crosses the head gasket and returns through three lengthwise head passages to the front of the engine and back into the radiator.

The larger two of these passages run through the port side of the head just above the spark plugs and theoretically account for 70% of the return volume. The remaining 30% is handled by a smaller .112" diameter passage that must be snaked through a number of obstacles inside the starboard side of the head.

Looking into the ends of the drilled-through holes, the hole pairs making up the two larger port-side passages appeared to be dead straight and to meet up as expected. However, both holes making up the smaller starboard-side passage appeared to curve downward toward the face that will eventually contain the combustion chambers. The two holes appeared to meet as expected, but their curved trajectories were worrisome since this passage passes within .037" of the yet to be machined combustion chambers.

Next to be machined were the intricate surfaces around the spark plug wells which required a lot of port-side machining time. Since the plugs screw into the head at 39 degree angles, they needed their own machining setup. The bores were drilled and threaded and their mounting surfaces finished in a separate angle block setup to minimize plug leaks.

The pent roof combustion chambers were machined next. It was during this operation that I discovered the troublesome coolant passage had indeed wondered into the space reserved for three of the six combustion chambers. Looking at the depths of the resulting grooves, it was clear the passage had wondered off some .050" from its intended trajectory.

Normally, I'd have scrapped the part and started over. But, I couldn't come up with a drilling technique that I could be sure wouldn't have the same problem. The first inch of those holes were drilled with an almost new jobber length drill and then completed with a brand new (and expensive) Gurling drill designed especially for deep holes. Peck drilling (.1" pecks) was used along with plenty of WD-40 and compressed air for chip control. In addition, the workpiece had been well supported and indicated to the quill.

After a couple days of rationalizing, I managed to convince myself that tiny passage probably wouldn't have flowed its full share of return coolant. And, compared with cast iron, aluminum's 5X thermal conductivity might make up for not having the passage at all.

I eventually decided to continue on with the current workpiece. Two lengths of snug-fitting drill rod augmented with high temperature Loctite were pressed into each end of the wonky passage in order to fill it and to seal the three affected combustion chambers. After a couple days cure, the surfaces inside the combustion chambers were re-machined to blend in the filler rod.

The top-side of the head was machined next and wound up being its own significant project. Although it turned out well, I caught myself not necessarily dreading another error that might force me to scrap the part and start over.

The front end of the block included a raised boss for the coolant return fitting and was machined next. An o-ring'd 90 degree elbow was designed at the same time to insure compatibility, but it will be machined later.

The intake and exhaust manifolds will eventually attached to the head's starboard side. Their ports will be drilled after the valve cages are installed. - Terry

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gbritnell

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Terry,
An absolute thing of beauty! You did the head proud! When making complex parts I always start to pucker when I have many hours spent and get to the final operations knowing that at any minute disaster could happen.
gbritnell
 

johnmcc69

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Incredible detail all around!
Hats off to both of you & George for your wonderful design & build skills!

John
 

Willyb

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Absolutely amazing work Terry. It's going to be a winner.
Cheers
Willy
 

kvom

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Do you put screws in the threaded holes before bead blasting?
 

propclock

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That is beautiful. It needs a clear lexan valve cover IMO.
Thanks as always for sharing .
 

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