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I haven't written a long article in quite a while.

SteveD recently started a thread about an intake manifold swap in which we discussed how to bring the 351C 4V up to pre-smog specification. Ever since then I've had this bit of history running around inside my head.

I hope you enjoy & I humbly submit the following historic info:

Few people realize that the state of California established automotive tailpipe emissions standards in 1959, the first tailpipe emissions standards found anywhere in the United States. The U.S. Clean Air Act of 1963 was the first federal legislation regarding air pollution “control”. All further federal air pollution control legislation has been enacted via a series of minor amendments and two major amendments (1970 and 1990). One amendment, the Motor Vehicle Air Pollution Control Act of 1965 established the first federal automobile tail pipe emissions standards, which became effective as of model year 1968. The new national standards for 1968 were modeled after California’s standards for model year 1966.

Model year 1968 was therefore a turning point for the thundering engines of the muscle car era. The tail pipe emission laws were written in such a way that they not only limited the percentage of pollutants in tail pipe emissions, they also limited the quantity of pollutants an engine was permitted to exhaust into the atmosphere over a given period of time, under prescribed test conditions. Limitations in the quantity of pollutants impacted high rpm performance engines and engines of larger displacement more than they impacted standard engines and engines of smaller displacement. High compression - high revving engines such as Ford’s dual quad 427 and high performance 289 were replaced in 1968 by a new breed of performance engine typified by the 428 Cobra Jet. As of 1968 camshafts had less duration and less overlap, compression ratios were lower, and carburetors were calibrated leaner. The amount of air pollution control equipment found on US automobile engines increased while the horsepower ratings generally decreased.

The concern for leaded gasoline’s effect upon public health was decades old even in the 1960s. Renewal of this concern lead to a movement in 1969 to eliminate lead in gasoline, and the auto corporations were supportive of the movement. Voluntarily lowering automotive engine compression ratios was a way for the auto corporations to support the movement since lead was used to boost gasoline octane. GM lead the way, model year 1970 was the last year for high compression engines at General Motors. Ford followed GM's example and eliminated high compression engines from their fleet before the end of model year 1971. If lead wasn’t utilized to boost gasoline octane, the prevailing belief was only low octane gasoline would be available. Engines equipped with 4 barrel carburetors were traditionally designed by the US automakers with higher compression ratios. Reducing the octane of gasoline obviously impacted high compression engines more so than low compression engines which were already designed for low octane gasoline.

Up until 1970 state and local governments had been primarily responsible for addressing the air quality issues identified by the Federal government. Implementation of air pollution reduction programs had been inconsistent from state to state and the enforcement of air pollution regulations had not been altogether effective. Testing revealed that more than half of the cars manufactured during model years 1968 and 1969 failed to meet the tailpipe emission standards set by the Federal government for those years. Improvements in air quality were not progressing at a pace acceptable to the public, lobbyists and politicians; therefore policymakers passed the Clean Air Act of 1970. Although technically an amendment to the original Clean Air Act of 1963, the Clean Air Act of 1970 was a complete make-over of the 1963 legislation and its subsequent amendments. It was very aggressive legislation which set more demanding standards that progressed at an accelerated pace. The Clean Air Act of 1970 also increased the role of the Federal government in implementing air pollution control programs and enforcing air pollution regulations. The Clean Air Act of 1970 was often referred to as the "Muskie Act" because Senator Edmund Muskie of Maine played a major role in drafting the bill.

The Muskie Act originally mandated that all states and regions of the United States had to attain clean air status by 1975, in terms of automobile tailpipe emission that meant most automobiles sold in the United States would be equipped with catalytic converters by 1975. Leaded gasoline poisons (i.e. renders ineffective) the catalyst in catalytic converters, so the use of catalytic converters became a secondary mandate for the elimination of lead in gasoline. The movement to eliminate lead in gasoline actually preceded the passage of the Muskie Act by more than a year however.

US Ford withdrew support from all racing in autumn 1970, "except for limited drag racing and off-road racing support on a divisional level and dealer level" to focus engineering resources (personnel, time and budget) on keeping up with government mandated safety regulations and tailpipe emissions regulations. To reduce tailpipe emissions to levels established by the new standards in the short period of time set forth by the Muskie Act placed unreasonable demands on the diminishing economic resources of the auto corporations and exceeded their technologic limitations. By mid-decade the government realized the deadlines set for auto tailpipe emissions were overly ambitious, and the emissions compliance deadlines set by the Muskie Act were extended.

I began this story summarizing the US tailpipe emission laws and the conversion to unleaded gasoline because Ford began manufacturing the 351C in August 1969, a few months after the beginning of model year 1970. It came on the scene as compression ratios were being lowered and lead was being removed from gasoline. The Muskie Act became law only months after the 351C went into production. Each year of its 5 year production history was impacted by the removal of lead from gasoline and the Muskie Act’s demanding standards and accelerated pace. It was an era of rapid and continual change for the auto industry. The performance goals Ford had for the 351C 4V were superseded by the need to adapt its engines to the use of un-leaded gasoline and to comply with the mandates of the Muskie Act. For reasons already explained the specification of the low compression 2 barrel carburetor version of the 351C remained basically unchanged throughout the 5 years it was manufactured in the US, but the 4 barrel carburetor equipped 351C was offered in 3 distinct versions in that same time period, and each version was subjected to annual changes.

For the readers not familiar with the terminology, the 351 Cleveland engines equipped with 4 barrel carburetors were manufactured in 3 versions we refer to using Ford's engine codes for those engines; i.e. the M-code engine, the Q-code engine, and the R-code engine. The 2 barrel carburetor version is referred to as the H-code engine for the same reason. In Ford terminology a 351C equipped with a 4 barrel carburetor was referred to as a 351-4V; 4V did not mean 4 valves as it does today, rather it meant the carburetor had 4 venturis. For the same reason a 351C equipped with a 2 barrel carburetor was referred to as a 351-2V. All 3 versions of the 351-4V were tuned for higher rpm with cylinder heads having raised intake ports of larger cross section than the heads found on the 351-2V. Those heads were known as 4V heads because they were designed for engines equipped with four barrel carburetors. The 4V heads were also initially equipped with larger 2.19" intake valves and 1.71" exhaust valves. The cylinder heads installed on 351-2V engines were referred to as 2V heads, they were equipped with 2.04” intake valves and 1.65” exhaust valves.

Engineers believed the lead contained in gasoline cushioned valves and valve seats as engines were operating, thus reducing valve and valve seat wear. Ford engineers decided to apply an aluminized coating to the valve faces to cushion the valves and valve seats in place of the cushioning that had been provided by lead. The 351 Cleveland valves were of two piece construction wherein the heads are joined to the stems by a friction welding process. This should not be considered inferior or unusual; it is standard practice to manufacture automotive valves this way. The 351 Cleveland valves were manufactured to the same standards of quality and durability Ford valves had always been manufactured. However as a final step in the manufacturing process the aluminized coating was applied to the valves by heating up the heads and spraying liquid aluminum on the valve faces. When this was done it crystalized the metal in the heads which made them brittle and therefore more prone to breaking. The factory OEM 351 Cleveland valves (both 2V and 4V) have a history of the heads developing cracks and breaking off the stems while the motor is running; not because the valves were of two piece construction, but because the heads were brittle.

In model year 1970 the M-engine code designated a 351 cubic inch 4V motor with a low-lift hydraulic tappet camshaft and a small 630 cfm 4 barrel carburetor. It was the lowest priced, entry level performance engine. The first couple of months of production the 351-4V was actually a 351W, the 351 V8 manufactured in Windsor Canada. The 351C, manufactured at Cleveland Engine Plant number 2, was a little delayed going into production. The Q-engine code in 1970 designated the 428 Cobra Jet. And the R-engine code designated the solid tappet 428 Super Cobra Jet. The 351-4V was equipped with 4V cylinder heads having quench style combustion chambers and was rated at 11:1 compression, which would have required super premium fuel, a commodity which was on its way out. So while Ford did not revise the rating on paper, the 351C-4V went into production with an actual compression ratio of 9.95:1. The output was rated at 300 SAE "gross" horsepower.

The 1971 engine manuals list both the M-engine code (351-4V) and the Q-engine code (351-4V-GT) in the engine code data section. This indicates the Q-code engine was planned from the beginning of the model year. However, although the Q-code designation had been assigned to the new 351-4V-GT, the engine manual contained no details about the engine. This indicates the Q-code engine's specification had not been determined at the time the engine manuals were printed. Whether or not it was planned to happen this way I don't know, but the Q-code engine was not made available until May 1971. From the point of view of vehicle production data I am satisfied to say that rather than wait for 1972 to introduce the new 351 Cobra Jet it was "phased-in" at the end of the 1971 model year.

What happened is this. The 351-4V-GT was delayed going into production. No doubt the new mid-size performance engine was originally intended to be a high compression engine, but Ford had to scramble and revise the engine's specification for lower compression and lower tail pipe emissions. So the M-code engine was offered at the beginning of the 1971 model year as a low-priced, entry level performance engine. Its specification was similar to its 1970 specification; it was equipped with a small 630 cfm 4 barrel carburetor and rated at 285 SAE "gross" horsepower. The advertised compression ratio was lowered to 10.7:1 although the actual compression ratio was 9.59:1; this was accomplished by increasing the volumes of the 4V cylinder head quench style combustion chambers by 3.3cc per cylinder. If you wanted the top performance motor in your Ford or Mercury at the beginning of model year 1971 you purchased the C-code engine, which got you the 429 Cobra Jet rated at 370 SAE "gross" horsepower. There was also a J-code solid tappet 429 cubic inch motor option, i.e. the 429 Super Cobra Jet, rated at 375 SAE "gross" horsepower.

The big changes occurred about May 1971, almost the end of the 1971 model year. The C-code and J-code engines, which were high compression engines, were both "phased-out" of production, as the new low compression (rated at 9.0:1) Q-code 351-4V-GT, i.e. the 351 Cobra Jet, was “phased-in”. The 351 Cobra Jet was rated at 280 SAE "gross" horsepower, it was equipped with a high-lift hydraulic tappet camshaft, 4V cylinder heads having open style combustion chambers, and a 750 cfm Autolite carburetor. The 1971 Q-code engine was manufactured less than 2 months. It became Ford’s top performance motor aside from the 330 SAE "gross" horsepower R-code 351 HO engine (i.e. Boss 351) which was a limited production "homologation" engine.

The 1971 engine manual did not list an R-code engine in the engine code data section; it listed the G-code 302 HO engine (Boss 302). Ford was making the transition to low compression engines however, which meant model year 1971 was the last opportunity to homologate a high compression 351C racing engine. So the plans to use the 302 HO engine in the 1971 Boss Mustang were dropped, and Ford engineers quickly designed a 351 HO engine to replace it. The R-code engine was therefore a little late in being offered to the public (along with the Boss 351 Mustang); it appears to have been manufactured in low numbers between November 1970 and July 1971. The timeliness of this decision made it possible for Bud Moore to race the "Boss 351" in NASCAR beginning 1972. This also left Boss 302 enthusiasts with a good supply of service parts having 1971 casting codes. The R-code engine was equipped with a solid tappet camshaft, a 750 cfm Autolite carburetor, 4V cylinder heads having quench style combustion chambers, 8cc pop-up dome pistons and it was specified as having 11.1:1 compression, although the actual compression was about 10.63:1.

The Q-code and R-code engine codes, which had been assigned to the pair of high performance 428 engines in 1970, were thus re-assigned to the 351 engines in 1971. Ford accomplished what it had been planning to do for at least half a decade; they replaced the 7 liter high performance motors with smaller mid-size V8 performance motors. The output of the 351 Cobra Jet must have been originally intended to be about 330 horsepower, which was close to the output rating of the 428 Cobra Jet, but the Muskie Act took its toll on the output of the 351 Cobra Jet.

1971 was the last year for high compression engines at Ford; they had in fact phased-out many of them before the end of the 1971 model year. There were no high compression engines in Ford's engine line-up in model year 1972. The last two months of the 1971 model year were also the only months in which all 3 versions of the 4 barrel carburetor equipped 351C were offered simultaneously. Although the M-code 351-4V could have occupied the middle ground between the high performance Q-code 351 Cobra Jet and the H-code 351-2V, no such engine was manufactured in 1972. The M-code designation was not assigned to any engine in model year 1972 or later.

For model year 1970 Ford had manufactured a total of 7 different performance engines as standard equipment or optional equipment for various models among its fleet of automobiles; for model year 1972 it manufactured only two … the 351 Cobra Jet and the 351 HO. The US automakers adopted specifying the output of their engines as SAE “Net” horsepower in model year 1972, thus the output of the 351 Cobra Jet was specified as 266 "Net" horsepower. The camshaft timing of the 351 Cobra Jet was retarded by four degrees, which lowered the "dynamic" compression ratio a small amount. The 1972 R-code 351 HO engine was not listed in the engine manual’s engine code data section for the second year in a row; and there was no 1972 Boss Mustang planned, the Boss Mustangs were a thing of the past. But engineers at Ford, determined to offer something better than the Q-code version of the 351C, found the time and budget to modify the R-code 351 HO for low compression & lower emissions. They equipped it with 4V cylinder heads having open style combustion chambers, flat top pistons and a solid tappet camshaft having shorter duration but higher valve lift. This revised 351 HO engine was made available late in the model year rated at 275 "Net" horsepower. It was manufactured in even more limited numbers than it had been in 1971; it was manufactured between January 1972 and about June 1972.

In model year 1973 Ford manufactured only one performance engine … the Q-code 351 engine. The compression ratio of the Q-code engine was lowered to 8:1 by increasing the volumes of the 4V cylinder head open style combustion chambers by 3cc per cylinder and adding 5.8cc dishes to the tops of the pistons (two valve notches plus a 5.8cc dish gave the 1973 piston tops a total volume of 8cc). It was equipped with exhaust gas recirculation, and smaller 2V size valves were installed in the large port 4V cylinder heads to restore the low rpm power lost when the compression ratio was reduced. The engine was rated at 246 "Net" horsepower which was the highest output engine offered by Ford outside of the big 460 V8 offered for the "biggest and heaviest Fords". The output of the 460 V8 was rated about 268 horsepower in that model year. There was no R-code 351 HO engine manufactured in 1973.

Model year 1974 was the last year the 351C was manufactured in the US, the Q-code engine's specification was unchanged from 1973 but the output rating rose to 255 horsepower. Ford never manufactured the 351C in a version that realized the engine’s full potential due to the tail pipe emission regulations which impacted the engine’s specification year by year since its introduction. The 351C did acquit itself admirably however when it is compared to other engines manufactured in the same era. Here’s the outputs of the competition’s top V8’s for 1974:

• Pontiac Trans Am Firebird (Super Duty) 455 cubic inch V8 – 290 horsepower (limited production)
• Chevrolet Corvette (LS4) 454 cubic inch V8 – 275 horsepower (limited production)
• Chrysler (Magnum) 440 cubic inch V8 – 275 horsepower (limited production)
• American Motors 401 cubic inch V8 – 255 horsepower
• Buick 455 cubic inch V8 – 255 horsepower
• Ford 351 cubic inch V8 – 255 horsepower
• Chevrolet Corvette (L82) 350 cubic inch V8 – 250 horsepower
• Chrysler 400 cubic inch V8 – 250 horsepower
• Pontiac 455 cubic inch V8 – 250 horsepower
• Chevrolet Camaro Z28 350 cubic inch V8 – 245 horsepower
• Chrysler 360 cubic inch V8 – 245 horsepower
• Chevrolet 454 cubic inch V8 – 235 horsepower
• Chrysler 440 cubic inch V8 – 230 horsepower
• Oldsmobile 455 cubic inch V8 – 230 horsepower
• Pontiac 400 cubic inch V8 – 225 horsepower
• American Motors 360 cubic inch V8 – 220 horsepower
• Cadillac 472 cubic inch V8 – 220 horsepower
• Ford/Lincoln 460 cubic inch V8 – 220 horsepower
• Cadillac 500 cubic inch V8 – 210 horsepower
• Oldsmobile 350 cubic inch V8 – 200 horsepower
• Pontiac 350 cubic inch V8 – 200 horsepower
• Buick 350 cubic inch V8 – 195 horsepower

The Q-code engine was not smog certified for California for 1974; California certification was a complete separate process from federal certification. Therefore the Q-code engine was not available as an option in cars sold in California. The Q-code 351 was standard equipment in Panteras however, not an option, and California was the largest market for the Pantera. Therefore Ford re-documented all 1974 Panteras destined for California as 1973 vehicles in order to get around California's 1974 tail pipe emissions certification.
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It is a sad quirk of history that the 351C was introduced right at a time when all of it's beneficial design features had to be curtailed due to legislative reasons.

It was the right thing at the wrong time.

If it had been able to hang on until the modern era of electronic control, fuel injection and engine management as did the smallblock Chev and smallblock Ford, all of it's difficult pollution control issues could have been eliminated without the detrimental effects on it's performance.

It could have taken it's rightful place as a "super engine" and been in far more widespread use.

The pre-historic pollution control devices and procedures of the seventies were responsible for the view that it was not viable to continue with it.

It hung on in Australia because pollution control legislation was not as strict as the US at the time and Ford Australia had discontinued smallblock production and put everything into retooling for the 351C.

The Australian market is small and Ford Australia, after such intensive investment, could not afford to go backwards so they were going with the 351C come hell or high water. So it lasted on for another ten years or so.

Some silly view in the eighties that nobody wanted to buy a car with a V8 led to it's demise in Aus.
There is something quite baffling about Ford's decision to discontinue the 351C.

It is apparent that they felt the 351C was not a viable power plant to adapt to the new pollution control measures being implemented at the time. Preferring to go back to the Windsor engines as they felt that design was more easy to adapt.

But then they continued on with the 400C and later the 351M, both using many 351C components and designs.

Surely those two engines would have been as difficult to modify, from a production viewpoint, as the 351C when it came to pollution issues ?
When the 351C was introduced Ford informed the press and their own employees that the engine was planned for 5 a year production run. I don't know why it was only going to be produced for 5 years, but since the announcement was made in 1970, I suspect it had nothing to do with tailpipe emissions compliance.

It was emission that finally lead to the engine's demise in the US (351M & 400) however; and probably Australia too (302C & 351C). The engines were cancelled the same year (1982) on both continents. Of course the engine lingered on in Australia at least through 1984, 2 years after its production officially ceased. The notch in the piston dome providing clearance for the canted intake valve made it necessary to situate the ring package lower on the piston. Hydrocarbons collect in the gap between the piston & cylinder wall above the top ring. Since the ring package sits lower in the clearance, more hydrocarbons collected, thus raising the engines hydrocarbon emissions.

If they had modified the Cleveland intake valve geometry just enough to eliminate the notch in the side of the piston, thus allowing the ring package to be raised, the head would have made a nice performance head for the 5.0 HO engine. A 1985 version of the Boss 302. I think it would have made sense from a marketing stand point, and made a few extra horsepower too.
Yes with a carb & exhaust change. Unlike the engine in the 1971 GT HO Phase III, the 1971 Boss 351 was equipped with cast iron exhaust manifolds and an emissions carb. I've run a Boss 351 on a chassis dyno with the following changes:

Removed rev-limiter
Hi rpm points
Boss 302 Holley 780 carb, over the counter from Ford
Ford aluminum manifold for the Holley carburetor D1ZX-9425-DA
Headers grafted in to the factory exhaust system.

The car made 290 bhp at about 6000 rpm on the chassis dyno, which equates to about 370 bhp at the flywheel. That's with the factory mufflers which were rather restrictive, the water pump & power steering pump were running too. We could have squeezed a few more ponies out of it with a Shelby (Blue Thunder) intake manifold and Cadillac mufflers.

The car had 3.91:1 gears and a 4 speed top loader off the showroom floor, it was a nice strong running street car. It needed traction bars however. The engine ran just as strong with the factory "505" hydraulic cam too.
Last edited by George P
Originally posted by George P:
When the 351C was introduced Ford informed the press and their own employees that the engine was planned for 5 a year production run. I don't know why it was only going to be produced for 5 years, but since the announcement was made in 1970, I suspect it had nothing to do with tailpipe emissions compliance.

It was emission that finally lead to the engine's demise in the US (351M & 400) however; and probably Australia too (302C & 351C). The engines were cancelled the same year (1982) on both continents. Of course the engine lingered on in Australia at least through 1984, 2 years after its production officially ceased.

A 5 year production run....That is bizarre.

It seems like a lot of design work and tooling up for such a short run, unless the 351C was planned as a intermediate step before the release of a more advanced design.

But that didn't occur, Ford seemed as if they were not sure of what to do at the time and went backwards to the older Windsor design. But then funny decisions get made by management !

In Aus it was not so much the emissions (although i imagine it would have played a part) but rather fuel economy issues that brought the 351C to a end.

Some genius in Ford Aus decided gasoline was getting to costly and big gas guzzlers were no longer appealing to the public.

So Ford Aus went to a all 6 cylinder line up for their large body cars and convinced themselves that no V8s would ever be sold again.

Of course GM had a different view and absolutely cornered the V8 market until Ford came to their senses some years later and started offering the imported 5 liter Windsor in some models.

As i said: funny decisions get made by management !
I was doing some research on the date code of a 351. I could not understand why all the references showed them as starting in 1970 but the date code indicated the Cleveland was a 1969 block; specifically I think Dec 15th.

After a little research I found a handful of Mustangs got a 1969 block from the last two weeks of December; so if you have a Pushbutton it would be worth seeing what the date code of the engine is. I believe Dec 15 1969 would have been one of the first Cleveland blocks ever in production.
What is the FIRST production date of any C engine installed in anything. Deduct three weeks and that is the date one would expect to see on the block casting date.

That is how Ford works. They change for no one.

Inquire with MCA. Ask what is the earliest known production date of a 351c Mustang.

The truth lies within that answer presuming the Mustang was the first line to get the C?

The 70 4v C's are D0...casting numbers. That is a 70 MODEL year. DEPENDING on when that model first was assembled, the castings were done earlier.

Is the Cleveland a half year introduction? That would make the only sense on the late casting dates.

Incidentally, the 71 Boss 351 4 bolt block is a modified 2 bolt D0AZ (I think it's AZ) block.
They are very rare and hard to find.

They offer NO benefit to using as a "performance block". The D2 block was intended to be the "performance block" and is the one that was "legal" for NHRA Pro Stock back then.

That's where the history of cracking through the main web into the bore comes from.

10,000rpm launches don't do a body good?
The earliest 351C "production parts" have August 1969 casting date codes. But it was a couple of months later in the year before assembled engines started showing-up in cars. Whatever source Gary is quoting is fundamentally correct, the engines weren't installed in anything until around November or December.

The 351C 4V was marketed in magazine ads and other media during the second half of 1969. But if you went to a Ford dealer in September 1969 and ordered a 1970 Mustang with an M code engine, it arrived at the dealership 6 weeks later equipped with a 4 barrel version of a 351W engine. By January 1970 the supply of 351C engines was rolling, just in time for one to be installed in that yellow Pantera that made its public debut in March 1970, at the Monza race track near Milan, Italy; then debuted in America at the New York and Los Angeles Auto Expos in April and May of 1970.

Cleveland engine plant #2 went through a very expensive renovation and expansion in preparation for producing the 351C. Those improvements took a little longer to complete than anticipated, delaying the beginning of production. Ford installed all new machinery, the latest most accurate machinery on the market, and they installed an all new computerized manufacturing system, which had to be programmed, started-up, tested, revised, etc. Typical of any computerized manufacturing system.

The cracking of the block mentioned by Doug was a result of operating the engine, equipped with the stock "partially counterweighted" crankshaft, at engine speeds in the range of 8000 to 10,000 RPM. Partially counterweighted cranks exert a tremendous bending force which impacts the mains at bearings no. 2, 3, and 4.
Ford had a lot of "irons in the fire" in 1969.

The second half of 1969 was a time of change for Ford. It was the beginning of a new fiscal year, and the beginning of model year 1970. The 1969 racing season was in full swing. The US economy was in a recession, unemployment would rise from 3.5% in October 1969 to 6.0% in October 1970.

CEO Henry Ford II believed the time had come for him to make changes that would improve Ford's public image, to align the corporation with the changing social climate of the US, and to bolster the corportation against financially hard times.

(1) He fired Bunkie Knudsen in September (19 months after his arrival in Feb 1968)

(2) He announced the corporation would spend millions of dollars to place emission controls on the smoke stacks at its factories (something the citizens of Dearborn had lobbied for over many years)

(3) He announced the corporation would spend millions of dollars on a new facility to study the reduction of automobile tail pipe emissions

(4) He announced the corporation was cutting its 1970 racing budget by 75%. The racing budget was administered by the Special Vehicle Department, which had been part of the Engineering Division since 1967. By reducing the racing budget the Engineering Division would have more funds available to work on improving passenger safety and reducing tailpipe emissions.

Don Frey (known as the man behind the Mustang's creation, and the Bronco as well) was also one of the men behind Ford's performance cars and racing programs. When Don Frey moved from the Marketing Division to the Engineering Division in 1967 he took the Special Vehicle Department with him. This is how the budget for racing was relocated in 1967 from "marketing" (where it belonged) to "engineering". Some feel the racing program may have survived this era if its budget had remained in marketing.

The picture below is Henry Ford II on the left, Don Frey on the right.


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  • deuce_and_frey
Here was a site which talked about it some:

"We receive many phone calls from classic Mustang enthusiasts inquiring if the engine in their 1969 or 1970 Mustang or the 1969 or 1970 Mustang they are contemplating purchasing is a 351 V-8 Windsor or a 351 V-8 Cleveland. First of all, virtually all 1969 351 V-8 engines were Windsors and virtually all 1970 351 V-8 engines were Clevelands. There are a few exceptions. Over the years we have seen a few 1969 Mustangs with factory installed Cleveland engines. By checking the build dates of these Cleveland 1969’s we found that in every case these Mustangs were produced in the last week or two of 1969 production when perhaps the factory ran out of Windsor engines."
OK, after readings Gary's last post, here's my issues with K.A.R.

During 1969, 1970, 1971 there was an M code engine option. It was a 351 V8 with 4 barrel Autolite/Motorcraft 4300A carburetor, 11:1 advertised compression, and ostensibly 300 BHP. Ford doesn't specify where that engine was manufactured.

The earliest 351C "production" castings more or less had August 1969 date codes (9H). Apparently there are "some" 4V heads out there with late July 1969 casting dates (9G22 specifically).

Here's a link to an old spread sheet for 4V cylinder head castings, including dates. The data was collected from the members of the Clevelands Forever Forum: 4V Cylinder Head Spread Sheet

Ford's production year is a fiscal year. This is where confusion often arises. The 1969 production year ended approximately June 30, 1969. As of approximately July 1, 1969 Ford geared-up to begin production of 1970 models. In spite of what Doug has written, a 1970 model year part, such as a D0AE block, can and frequently does have a casting date of the previous year ... like 9H (9 meaning 1969, H meaning August) in this example. Check-out the cylinder head data linked above for many examples. The explanation is simply that the 1970 model year began mid-1969.

However for a 1969 Mustang to have been factory equipped with a 351C was basically impossible ... since "production" 351C engine parts weren't being cast until August 1969. I know beyond a doubt that the "early" 1970 Mustangs ordered with M code engines were equipped with 351W 4V engines. Those 1970 models went on display at dealerships in September 1969, and were thus manufactured sometime in July 1969.

Unless of course those 1969 Mustangs were equipped with engines manufactured from SK & XE parts, which I strongly doubt. The experimental (SK & XE) 351C parts, which were also race parts, pre-dated the production parts by YEARS. But that's a whole different batch of parts from the production parts.

One last tidbit of history and then I'm off. The first production engine to be manufactured with Cleveland cylinder heads was not the 351C, it was the 1969 Boss 302. That car was late going into production, the 1969 Boss 302 Mustangs were manufactured in approximately Spring 1969. The Boss 302 engines pre-date the production of the first 351C by about 6 months. But the Boss 302 engine castings (including the heads) were not cast at the Cleveland casting plant, nor were the Boss 302 engines assembled at Cleveland Engine Plant #2.

The 351C 4V ad below, from a Fall 1969 magazine, says you can order the "new" 351 4V for your 1970 Torino, Montego, Mustang or Cougar. It makes it seem Donnie Allison won the Alanta 500 with a car powered by a 351C, but it really only says they were testing "better ideas" found in the 351C with their race cars.


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  • 351C_4V_ad
Last edited by George P
I agree with George. Unless you have the Marti report or documentation to prove your 69 Mustang came with a 351C, then you do not have one. People often mix up casting numbers and casting dates. Manufactures did not switch and retool for the new model year over night. And the manufacturing year/model year is not the same as our calendar year. I do not believe any 69 Mustang ever came through with a 351C. Yes in 1970 an H-code 2 barrel could come through with a Windsor but not a M- code. These tales are often helped by early literature that was wrong and then continues to be misprinted. Just like the odd 68 GT 500 Shelby sneaking through with a 390 instead of a 428 or ordering a Galaxie with a 427 SOHC. Both legitimately dis-proven by their respective clubs and sanctioned judging associations, through research and actual manufacturer paperwork.
If your getting casting dates in the late months of 69 that is already well into 1970 production. Shelby's were considered late production and even them with casting dates starting in Aug and Sept of 67 are in 1968 model year cars. so a regular production Mustang with Nov/Dec 69 casting dates is definitely 1970 production.
Even now 2017 models of most manufacturers will be heading onto your local dealership lots fairly soon.

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