If It’s a Windsor, It’s a Small Block

Written by Don Stewart | 30 November 2007

We talk all the time about small block and big block engines in the  early V-8 Mustangs. But strangely, we almost never talk about medium block motors. In our conversations, I think most of us relate engine size to displacement; I know I’m guilty of that. We have a gut feeling about cubic inches and we categorize the engines accordingly.

Much of the time we’re wrong. We’re wrong when we exclude the medium blocks. And we’re wrong when we arbitrarily assign an engine size based on displacement. That’s because cubic inches don’t necessarily define block size. Block size is related to architecture and physical size not cubic inches. Block size is fairly well defined by bore spacing; the closer together the bore centerlines, the smaller the block. In the classic era beginning with 1962, Ford used three bore spacings spread among several engine families. The bore centers were: small block at 4.38”, medium blocks at 4.63”, and big blocks at 4.90”. First generation Mustangs used engines from four of the families. There was a heavy concentration of small blocks that came mostly from the Windsor family and to a lesser extent from the 335 family. Next came medium blocks from the FE family. Finally, big blocks came from the 385 family which contributed the one and only  true big block used in the pony car.

This month I’m going to run through a brief historical summary of the small block Windsor V-8s. The Windsor bullets came in various displacements and various power levels. They crossed through the 320 cid boundary sometimes used to separate small block from medium block but with the 4.38” bore spacing, they were all small blocks.

When I think about the Windsor engine, it’s usually because I need to separate the 351 Windsor from the 351 Cleveland, both small blocks. But the 351W is only a small part of the Windsor story. By-the-way, if you didn’t know or hadn’t guessed, the Windsor designation came from Ford’s Windsor, Ontario, Canada engine plant. Somehow the name became irrevocably linked to the family and it didn’t matter that a lot of the Windsors actually came from the Cleveland, Ohio, engine plant, including all of the early ones up through 1966.

Nevertheless, staying on track, the Windsor engines were introduced before there were Mustangs to put them into. The new family replaced the old Y-block V-8s and it first hit the streets in 1962 with an L-code version displacing only 221 cid. The engine was offered as an option for Fairlanes and Meteors at a gross horsepower rating of 145 with a 2-barrel carburetor. It was gone after 1963, having been upstaged that year by the introduction of a 260 cid F-code rated at 164 hp and a 289 cid version available in three power levels: the 2-barrel C-code rated at 195 hp, the 4-barrel D-code at 210 hp, and the K-code HiPo at 271 hp.

When the ‘64½ Mustang came along in April 1964, the F-code 260, was the original V-8 option. It was dropped from the option list after a few months and replaced by the D-code 289. Also available was the K-code 289 HiPo.

For 1965 and 1966 if you wanted a V-8, the 289s were the only game in town. The top of the ladder saw the same K-code at 271 hp, preceded by a 4-barrel A-code rated at 225 hp, and a base 2-barrel C-code at 200 hp. Never mind the Shelby version. That’s a story for a different time.

Ok, before I get too caught up in this evolutionary stuff, let me back up and tie the 221, 260, and 289 Windsors together by touching on some of the things they had in common. The family shared a thin cast block with the aforementioned 4.38” bore spacing. They all had a 2.87” stroke and the heads had two valves per cylinder in wedge-shaped combustion chambers. The different displacements were strictly a function of bore diameter with the 221 at 3.50”, the 260 at 3.80”, and the 289 at 4.00”.

The same 289s were available again in 1967 but now with more room available in the engine compartment, a (physically) larger engine was added to the option list for the first time. It was a 390 medium block (4.63” bore centers) from the FE family. More on the FE in a future article.

Early in 1968, you could still order the C-code 289 but another member of the Windsor family, a 302 cid version, soon appeared as its replacement. The 302 was available as a 2-barrel F-code rated at 220 hp and a 4-barrel J-code rated at 230 hp. For the first time since its introduction in 1962, the Windsor’s stroke was increased to gain the extra cubes. The stroke was now 3.00” with the 4.00” bore carrying over from the 289.

Moving into 1969, the 302 F-code was the base V-8 but the J-code was gone, replaced by the 4-barrel G-code rated at 290 hp. With 290 hp, the G-code suggested something special. To many of us at the time, it was very special and today we still salivate over it. That’s because the G-code had a street name that would give you chills. It was the “Boss 302” and it was made available to the public so that Ford could homologate its use for the Trans Am road racing series. The Chevy Camaro Z-28 was Trans Am’s top dog at the time and Ford needed a better Mustang to compete at the front of the pack. As a bit of trivia, originally it was the engine that was the Boss 302, not the car. But almost simultaneous with the introduction of the car, the popular vernacular of the day blurred the distinction between the engine and the car so that from the beginning the car was known as a Boss 302.

Was the Boss really a Windsor or did it just coincidentally have the same displacement as the F-code? The best answer is that it was definitely a Windsor but it was heavily modified for performance. Bore and stroke were the same. The block had the 302 dimensions but it was from the discarded tunnel port project with thicker cylinder walls and 4-bolt main bearing caps on 2, 3, and 4. It used a forged steel crankshaft, forged connecting rods, and forged pistons. The rotating assembly was balanced statically and then it was assembled and balanced dynamically. The pistons were similar in design to those in another small block engine family, the 335 series under development at the time. The heads also came from the 335 program.

The Boss’ nearly bullet-proof design and internals made it very reliable but the heads were the key to its power. They were free flowing and quench chambered with large canted and offset valves. For anyone keeping score, it was the first public appearance for heads that would very soon carry the name Cleveland. In addition to specialized Boss 302 duty, they would see mainstream use on the upcoming 4-barrel version of the new 335 engine.

Another new Windsor variant also made an appearance in 1969. In 2-barrel trim it was called the H-code and it developed 250 hp. With a 4-barrel and designated the M-code, it made 290 hp. It was the 351W and it was the beginning of one of Ford’s most successful engines, an engine that was used across much of the car and truck line, at one time or another, until 1997.

The 351W had the same 4.38” bore spacing as other Windsors but it had a deck height that was 1.3” taller to accommodate a longer 3.50” stroke, up ½” from the 302. The 4.00” bore was retained but the bottom end had larger main bearing caps and the connecting rods were more robust and, of course, longer. It had the largest displacement of any engine to come out of the Windsor family.

The 302 F-code and the G-code Boss configurations continued unchanged in 1970. The 351W in H-code trim was still available at the beginning of the year but it was in the process of being replaced by the 351 Cleveland also designated as H-Code and also rated at 250 hp, confusing to say the least. You had to look at the engine and know the difference between Windsors and Clevelands to tell which one you had. The M-code 351W was completely gone and in its place was another M-code. It was the 351C developing 300 hp trimmed out with a 4-barrel and the same heads used on the Boss 302. This was not as confusing as the H-code situation because if you had the M-code, you knew it was a Cleveland, there being no M-code Windsors in 1970.

Since I brought it up, here are some things you can easily check to differentiate between a 351W and a 351C:

351W

Upper Radiator Hose attaches to the water neck at the front of the intake manifold.

Valve Covers have six holddown bolts.

Spark Plugs are the larger 13/16” size.

351C

Upper Radiator Hose attaches to the top of the timing cover.

Valve Covers have eight screws.

Spark Plugs are the smaller 5/8” size.

For model years 1971 through 1973, the 302 F-code was the base V-8 and the only Windsor in the lineup. There were several other engines but none of them were Windsors.

That wraps up the summary of Windsors used in the first generation Mustangs. There’s no doubt that the family had a strong presence. Certainly, too, the family had two standout performance members and another member fitting a broad spectrum of needs. Respectively, they were the 271 HiPo and the Boss 302 performance engines plus the 351W that served Ford for 30 years.

There’s a bit more trivia to share. We know the 302 Windsor soldiered-on in the second generation Mustang II with the exception of the 1974 model year when no V-8s were available. And we know that it prevailed under the metric 5.0L designation throughout most of the third generation Fox years and then again during the fourth generation SN-95 years up through 1995. It was missing from the Fox option list only during model years 1980 and 1981 and that was due to EPA restrictions. But do you know what V-8 was offered during ‘80 and ‘81? Did Ford even have one that they could use? Well, no, Ford didn’t have one so they developed one. It carried D-code identity, it had 115 to 119 (net) hp depending on the model year, and it only had 255 cubic inches. But it was a member of the Windsor family and at 255 cid, it was the second smallest Windsor ever offered. Rather than develop the engine from the shorter stroke early Windsors, Ford chose to base it on the 302 with its 3.00” stroke. So with the stroke set, the 302 block was de-bored from 4.00” to 3.68” and the Windsor family had another iteration for three years. It was offered as the sole V-8 in ‘80 and ‘81 and in 1982, it was an option alongside the returning 5.0L (302).