Where to find a usable shop manual for a 1966 F100
The original Factory Shop Manual for the 1966 Ford F100 covers the chassis, drivetrain, braking, steering, and electrical systems. It is mostly useful for engine work on the 240 cubic inch six and the 300 V8, though the 352 and 390 V8s are covered in brief sections. The 302 didn't exist yet in '66, so if you're swapping in a small-block later, the manual won't help much beyond basic torque specs. You can buy a reprint from several sources. Haynes publishes a third-party manual that is easier to read but misses some factory-level detail like the wiring diagrams for the dash panel and the cowl area. The original Ford manual is available as a PDF through vendors like FordPartsNow, eBay sellers who scan originals, and the Ford Owners Club archive. The OEM reprints are usually sold as 8.5 by 11 inch booklets with black and white photos and line drawings. They look dated. They work fine. I've used both the Haynes and the Ford OEM reprint on the same truck. Here's the practical difference: the OEM manual has the correct sequence for checking valve clearance on the 240 six, including the timing marks on the harmonic balancer and the exact rotation method. The Haynes simplifies it to "rotate the engine" without explaining which mark to use. That detail matters when your feeler gauge keeps slipping because you're turning the wrong way.
Download and source notes for Shop Manual 1966 Ford F100
I don't host files, and linking to pirated copies isn't something I do. Search for "Ford Shop Manual 1966 F100 PDF" and you'll find the OEM version on sites like fordmanuals.info, etracmanuals.com, and eBay listings for physical reprints. The PDF versions floating around are usually scans of the 1966 Ford Truck Shop Manual, service publication number CMA-2003 or similar. File sizes run between 25 and 60 MB depending on scan quality. Lower quality scans make the wiring diagrams hard to read, so look for a listing that mentions high resolution or full page color. For the wiring diagrams specifically, the OEM manual's appendix on electrical diagnosis is where you want to spend time. Most people skip it and go straight to the wiring in the back, but the diagnostic sections for the lighting circuit, charging system, and starter relay are worth reading first.
What the manual actually covers in practice
The manual breaks into chapters roughly the same way every Ford service book from that era did: Chapter 1 — Engine mechanical: Valve adjustment, timing chain, oil pump removal, block deck milling clearances. The 240 six gets the most attention because it was the volume seller. Torque specs are listed in foot-pounds, not Newton-meters. The head bolt sequence is critical here, and it's shown in a diagram that isn't always intuitive. I once torqued the heads in reading order because the diagram was grainy, and ended up with a small leak at the intake manifold gasket that took three days to track down. Chapter 2 — Lubrication and cooling: Water pump removal is straightforward, but the manual doesn't emphasize that the upper radiator hose on the 1966 F100 is a known failure point. The original rubber hardens and cracks internally while looking fine externally. Replace it regardless of appearance. Same for the thermostat housing gasket — it's a paper gasket, and reuse is a bad idea.
Get the Full Details
Chapter 3 — Fuel and exhaust: Carburetor rebuilding for the Autolite 1B and 2B is covered, but the jet sizes aren't always listed for every emission level. If your truck was a California model, the carb setup differs from the rest-of-country version. Check your VIN decode or the emissions sticker under the hood before buying a rebuild kit. I bought a standard Autolite rebuild kit for what turned out to be a California 240 six, and the main jet was too large. Engine ran rich, smoked on deceleration, and wasted fuel until I found the correct part number cross-reference. Chapter 4 — Transmission and drivetrain: Manual transmission tear-down is detailed for the three-speed top-loader and the early four-speed. The floor shift linkage adjustment is often missed. The manual gives the spec but doesn't stress that the detent plate wear causes vague shifting, and new bushings alone won't fix it if the plate is already elongated at the gear positions you use most. Chapter 5 — Rear axle: Ring and pinion adjustment is covered, but the manual assumes you have a dial indicator and proper fixtures. If you don't, the section becomes theoretical at best. Setting backlash by feel with a prying bar and a feeler gauge works in a pinch, but the result won't be as good as a proper setup. Axle bearing preload is another area where the manual is light on practical guidance. Ford specified a break-in procedure that most people skip, and that's why rear ends whine after a rebuild.
Chapter 6 — Suspension and steering: Front spring replacement, ball joint inspection, and power steering box adjustment. The power steering pump relief valve adjustment on the 1966 model uses a specific tool that isn't mentioned by name in the manual — it's just referenced as "special tool." That tool is basically a small hose and a pressure gauge adapter that you can fabricate or borrow from a parts store loan program. Chapter 7 — Brakes: Drum brake adjustment procedure, wheel cylinder rebuilding, and proportioning valve location. The proportioning valve is mounted on the frame rail behind the driver side front wheel. It fails more often than people expect, and the manual's troubleshooting section is thin on this component. If your rear brakes are locking up prematurely during moderate stops, check the valve before replacing hardware.
Wiring diagrams — the part everyone dreads
The 1966 F100 uses a brown ground system with a single wire running from the battery negative to the frame, then from the frame to the engine and body. The dash wiring is notoriously difficult to trace because the factory used color codes that changed mid-year. Tan becomes light green in some harnesses. The manual's wiring section shows the colors but doesn't always flag this switch. I spent a weekend tracking down a phantom intermittency in the turn signal circuit on my truck. The manual pointed at the multifunction switch, which I replaced twice. Third time around I went back to the diagram and noticed the ground at the steering column was corroded under a bracket I hadn't seen before. Cleaned the ground, problem gone. The manual is accurate, but the diagrams assume you can see every connection point in a well-lit, disassembled engine bay. That's rarely the case.
Common mistakes when using this manual
The biggest issue I see is people treating the manual as a parts catalog rather than a procedure guide. The fastener sizes and torque specs are there, but the manual doesn't always list the replacement part numbers for wear items. You'll find the torque for the exhaust manifold bolts, but not the correct gasket part number. Cross-reference using a parts database or the Ford parts manual separately. Another mistake is ignoring the model-specific variations. A 1966 F100 with the Ranger trim has different interior panel fasteners than the base model. A Flareside bed uses different rear shock mounting hardware than the Stepside. The manual acknowledges these differences in footnotes, but they're easy to miss when you're reading quickly. The electrical section also assumes familiarity with Ford's color coding system. Hot wires are red, yellow, blue, etc. Ground wires are green or brown depending on the circuit. If you're not familiar with this, print the color code chart and keep it next to the manual while you work.
When the manual falls short
There are genuine gaps. The 390 V8 is covered but with less detail than the 300 and 240. If you have a 390, plan to supplement with engine-specific resources. The manual also doesn't cover any of the later emissions equipment additions that some 1966 trucks received at the factory or through dealer retrofit programs. If your truck has an evaporative emissions canister or a diverter valve, those parts and their routing are not in the book. For suspension work, the manual gives teardown steps but doesn't address the common rust issues that come with a 58-year-old truck. Frame rail repair, control arm mounting bolt extraction, and leaf spring eye bushing removal all require techniques the manual doesn't discuss because they're field problems, not factory procedures. The transmission sections are adequate for manual units. The automatic transmission coverage — particularly for the C4 and C6 — is superficial. If you're doing a complete rebuild, you'll want a dedicated transmission manual in addition to the Ford shop book. The Ford manual will get you through a drop-and-reinstall. It won't help with valve body machining or drum reconditioning.
How I actually use it
I keep a printed copy on a shelf next to the truck and use the PDF on my phone for quick reference when I'm under the vehicle. The OEM manual's diagrams are clear enough to read on a 6.5 inch screen if the lighting is decent. I bookmark the chapters I use most — engine mechanical, brakes, and suspension — and skip the rest unless I need them. When I'm doing a job I haven't done before, I read the entire relevant section first. Not just the steps, but the notes and cautions at the bottom of each page. Ford's service literature from this era includes warnings about things that will go wrong, and those warnings are usually accurate. The caution about not reusing the oil pan gasket on the 240 six, for example, is important. The original gasket is cork-rubber composite, and it compresses permanently on first installation. New gasket required. The manual is a reference tool, not a substitute for judgment. It tells you the sequence and the specs. It doesn't tell you that the bolt on the passenger side exhaust manifold bracket is seized and will snap if you just crank on it. You figure that out by being and paying attention.
