TORO-FLOW

THE OTHER GM DIESEL

The ’70s TV talk show host Tom Snyder was known for asking, “What goes through their minds?” when confronted with inexplicable human behavior. That might apply when pondering why GMC executives directed the development of the Toro-Flow diesel. Given the array of diesels the GMC truck line had to choose from, most notably those built by GM itself, it seems an odd way to spend money. Well, GMC execs saw a low-cost diesel gap in the medium-duty truck market. Yes, the GM two-strokes were widely available, but they were expensive and noisy. GMC was not averse to going outside the company for an engine, but none of the choices quite met the low-cost criteria either. Introduced in 1964, the Toro-Flow was the answer, but it had some baggage.

The development process for a four-stroke, low-cost diesel began in 1953 and was eventually synchronized with the development of a new 60-degree V6 gasoline engine to be introduced for 1960. This is not to say the diesels would be “converted gas engines.” They weren’t. It’s more accurate to say the gas and diesel V6s were concurrent developments to be built with similar architecture and on similar tooling. There was very little actual parts changeover.

The well-regarded GMC V6 gassers were initially offered in 305, 351 and 401 ci, but by ’62 had grown to 478 ci and later 379 and 432 ci versions were offered. They were one of the first V6 engines offered in the United States, and the 305-powered GMC fleet of light trucks, a deliberate snub of the Bowtie Stovebolt inline. But enough gasser drivel!

The Toro-Flow diesels debuted in 1964 in two displacements, 351 ci (the D351, 130 hp) and 478 ci (D478, 150 hp). A high-output model was also offered, the DH478, cranking out 170 hp. It’s been reported that GMC toyed with the idea of a diesel 305 V6 in the light trucks but it isn’t clear how far the idea went. Probably not very, given the light truck market of the day. It was common enough to see D351s swapped into GMC pickups by the handful of owners motivated to do it. It was a relatively easy swap, sometimes done on new trucks by the dealer.

The D351 was seen in the lightest tonnage models of the medium duty line and the D478 was seen in the heavier 4000 and 5000 lines, with the DH478 as an option. For 1965, certain models in the Chevrolet medium-duty line also appeared with the same Toro- Flow V6 diesels as an option, in addition to the 53 Series Detroit two-strokes. Chevrolet labeled it the Torq-Flow in some 1965 literature but reverted to “Toro” in later publications. It isn’t known if this was an error, a return dig at GMC, or an ill-conceived notion to be different. Chevrolet continued to offer the Toro- Flow in its medium-duty line into 1974, but it was a rare option.

For ’66, the D637 Toro-Flow V8 was introduced and rated at 195 hp. Concurrently, a DH637 was introduced with 220 hp. A funny sideline to the D637 V8 is that the ’67-72 637 gasser was, in many ways, a converted Toro-Flow 637 diesel with a lower compression ratio and a carburetor. The combustion chamber was in the piston, like the diesel, and the heads were flat like a diesel.

The Toro-Flow II debuted for 1969 but it was little more than a few reliability updates and a new engine color, a Detroit-like green replacing the earlier GMC orange or Cat-like yellow. The D351 was eliminated, as well as the standard power D478 and D637, making them all “DH” models. For 1972, GMC renamed them again, adopting the “Turbium” moniker and this remained until the end of production in ’74.

The Toro-Flow became a relatively popular marine diesel in pleasure craft due to its low cost. Crusader Marine, American Marine, Barr Marine Products and Daytona Marine offered converted V6 and V8 Toro- Flows. There were twin-turbocharged marine versions that never saw use on the road. A marine DHT478 cranked out 220 hp and the turbocharged DHT637 V8 made 300 hp. A turbocharged DH478 V6 made the road in the late ’60s GMC bus lines, but finding one is rare. The available books don’t show a turbocharged Toro-Flow V8 in trucks, though some unconfirmed sources claim they existed.

The “Toro-Flow” name was derived from the engine’s toroidal combustion chamber action, designed to induce a swirl to better mix the air and fuel. The Toro-Flow engines were all narrow 60-degree V-type engines and could be built with both right- and left-hand rotation. Both the V6 and V8 Toro-Flows used balance shafts. All the Toro-Flows were over-square, with the D351 having a bore of 4.56 inches and a stroke of 3.56 inches. All the other engines shared a 5.125-inch bore and 3.86-inch stroke.

The injection system came from American Bosch in the form of the PSJ rotary pump. That’s not one many people remember but it was used on a few engines in that era and is similar to the better-known PSB. It fed Bosch injectors that popped at 3,000 psi. Max full-load rpm was 3,200 for the V6 engines, 2,600 rpm for the D637, and 2,800 for the DH637.

The Toro-Flow has a rather notorious reputation and is known for two main problems, the American Bosch PSJ injection pump and head gasket failures. The word from back in the day was that regular head re-torquing eliminated most problems relating to head gaskets. The reputed PSJ pump issues are not clear. Various failures are also attributed to continuous hard use and high revving. Overall, Toro-Flows did better in the lighter duty applications than they did in the higher GVW trucks. They fared better in marine applications because those were mostly in pleasure craft. In either case, many parts are incredibly difficult to find, although there seems to be no shortage of remaining engines.

The Toro-Flow’s bad rap was rooted in reality but also needs to be viewed in context. They were some of the first diesels designed and built specifically for the medium-duty truck market of the ’60s, which at the time was a market still dominated by very well-proven gasoline engines. Strange as it sounds, that market was skeptical of diesels and not 100-percent ready for the change to diesel. Could GMC have done better, even on the tight budget they set for themselves? Sure. Let’s call just call the Toro-Flow an evolutionary step with some stumbles and give it a little respect for being first. DW

FREQUENTLY ASKED QUESTIONS

How did the Toro-Flow engines influence the development of future diesel engines?

The Toro-Flow engines played a pivotal role in shaping the future of diesel engine innovation. Just like a pioneer stepping forward to undertake a new challenge, these engines were among the first to explore new possibilities in diesel technology. Although not without their imperfections, the initial shortcomings of the Toro-Flow engines served as valuable lessons for the industry.

By identifying and analyzing the flaws in these early models, manufacturers were able to enhance the design, functionality, and efficiency of subsequent diesel engines. The lessons learned from the Toro-Flow’s experiences directly informed the development of more robust, reliable, and performance-oriented diesel engines that followed.

This process of trial and improvement helped set a foundation for continuous innovation, ultimately leading to the advanced diesel engine technologies we see today. Just as those learning from someone else’s first attempt can make their approaches better, the Toro-Flow engines catalyzed progress and paved the way for future advancements in diesel engineering.

What is the historical timeline and evolution of the Toro-Flow diesel engines?

The Historical Timeline and Evolution of Toro-FlowDiesel Engines

The Toro-Flow diesel engines have a fascinating history of development and adaptation from the mid-1960s to the early 1970s. Let’s explore the changes and milestones in their evolution.

1964-1968: Introduction of Toro-Flow

During this period, the Toro-Flow engines were first introduced, showcasing models such as the D351, D478, DH478, D637, and DH637. These engines were notable for their diverse range, providing various options for different output needs.

1969-1971: Transition to Toro-Flow II

In 1969, the line saw significant changes, transitioning to the Toro-Flow II. This phase marked the discontinuation of the D351 and several non-high output models. The focus shifted to enhancing performance primarily through the DH478 and DH637 engines. Although detailed technical modifications remain unclear, a prominent change included the engine color, transitioning from a Caterpillar-like yellow to a Detroit Diesel green.

1972-1973: The Emergence of Turbium Diesel

The evolution continued with the introduction of the Turbium Diesel line. By this time, only the DH478 model was prominently featured, with records of the DH637 models becoming scarce. While some sources suggest that Turbium engines were still mentioned in 1974, documentation from this period is limited, leaving certain aspects of these engines shrouded in mystery.

Overall, the Toro-Flow engines underwent significant transformations within a decade, adapting to changing performance demands and industry aesthetics. This evolution represents a noteworthy chapter in diesel engine history.

What are some anecdotes or experiences shared by users of Toro-Flow engines?

User Experiences with Toro-Flow Engines

Many users who had hands-on experience with Toro-Flow engines have shared their insights over the years. One user operated a DH478 in a Ford pickup for two decades and relied on the trusty old Motor’s Truck manual to maintain it. Though not having official documentation often meant improvisation, this didn’t deter passionate enthusiasts.

Reputation and Performance Challenges

The Toro-Flow engine was often humorously nicknamed with variations like “Toilet-Flow,” “Trouble-Flow,” and “Turdo-Flow,” highlighting its rocky start. Initial issues plagued these engines, primarily because they were run at 3200 RPM, leading to reduced lifespan. Once users adjusted the RPM to 2800, engine durability improved significantly.

Another challenge was the engine’s initial application in excessively heavy trucks. They didn’t handle hard lugging well, which contributed to their damaging reputation. However, some industries, like artesian water hauling, found them quite effective in water tankers, successfully operating fleets for around two decades once the kinks were sorted out.

Maintenance Tips

Maintenance was crucial for longevity. Users needed to regularly monitor the oil pump drive gear, which drove off the back of the camshaft similar to a gas engine. This particular component was prone to wear and tear, occasionally stripping out altogether. One user shared the best practice of inspecting this gear annually, which proved vital in preventing engine failure.

In summary, while Toro-Flow engines had a challenging debut, with proper tuning and maintenance, they served their purpose well in specific applications. Such shared experiences provide valuable lessons for enthusiasts and mechanics alike.

How did the Toro-Flow engines perform in terms of reliability and popularity?

The Toro-Flow has a rather notorious reputation and is known for two main problems, the American Bosch PSJ injection pump and head gasket failures. The word from back in the day was that regular head re-torquing eliminated most problems relating to head gaskets. The reputed PSJ pump issues are not clear. Various failures are also attributed to continuous hard use and high revving. Overall, Toro-Flows did better in the lighter duty applications than they did in the higher GVW trucks. They fared better in marine applications because those were mostly in pleasure craft. In either case, many parts are incredibly difficult to find, although there seems to be no shortage of remaining engines.

Reliability Challenges

The Toro-Flow engines, initially introduced with high hopes, faced significant reliability challenges. Designed as a diesel conversion of robust V6 gasoline engines, they were expected to capture the medium-duty truck market. However, they encountered numerous issues when put to the test.

• Performance Under Stress: The engines were notorious for not holding up under heavy workloads, especially in larger trucks requiring more power. This often led to critical failures, necessitating replacements with less efficient gasoline counterparts.
• Reputation and Adjustments: The engines suffered from a damaged reputation due to their initial shortcomings. Attempts to rectify these included reducing the engines’ RPMs, which improved longevity but couldn’t fully restore confidence.

Popularity and Market Reception

Despite notable engineering efforts, the Toro-Flow struggled to gain popularity. The trucking industry, demanding reliability and power, found the engines lacking. They were often over-applied, placed in vehicles too heavy for their capabilities, which compounded their issues.

Yet, there were those who appreciated the Toro-Flow for what it was—a noble effort that, while failing to meet its potential, showed promise in less demanding scenarios. Anecdotal evidence suggests they performed well in lighter duties and even in marine applications, where stress levels were lower.

In summary, while the Toro-Flow engines displayed some potential, they ultimately never achieved the reliability or popularity needed to dominate their intended market.

How did the Toro-Flow engines compare to other diesel engines of the same era?

The Toro-Flow diesels debuted in 1964 in two displacements, 351 ci (the D351, 130 hp) and 478 ci (D478, 150 hp). A high-output model was also offered, the DH478, cranking out 170 hp. It’s been reported that GMC toyed with the idea of a diesel 305 V6 in the light trucks but it isn’t clear how far the idea went. Probably not very, given the light truck market of the day. It was common enough to see D351s swapped into GMC pickups by the handful of owners motivated to do it. It was a relatively easy swap, sometimes done on new trucks by the dealer.

Toro-Flow vs. Competitors

The Toro-Flow engines were designed as a cost-effective solution for medium-duty trucks at a time when diesel engines were gaining traction in the market. Unlike other engines of the era, which were often expensive and challenging to fit into medium-duty chassis, the Toro-Flow was developed concurrently with the GMC 60-degree V6 gas engines. This shared tooling offered significant cost savings, though there was minimal parts interchangeability; the gas V6 and diesel V6 components were distinct.

In the late ’50s and early ’60s, diesel engines faced significant hurdles in the medium-duty market. They were plagued by issues such as cranky cold starts, low power, and a lack of fueling infrastructure. Despite these challenges, the Toro-Flow’s compact nature made it an attractive option for retrofitting in medium-duty applications.

The D and DH637 V8 Toro-Flows shared the V6 architecture. At 195 and 220 hp respectively, they compared to the bigger V8-265 Cummins of the era (785 ci, 265 hp @ 2,600) and the Caterpillar 1160 V8 was nearly the same displacement and output as the DH637 and, like the Cummins, was seen in the upper end of the medium-duty range. Strangely, both the Cat and the Cummins V8s also shared a somewhat tarnished reputation.

Technical Features

The “Toro-Flow” name was derived from the engine’s toroidal combustion chamber action, designed to induce a swirl to better mix the air and fuel. The Toro-Flow engines were all narrow 60-degree V-type engines and could be built with both right- and left-hand rotation. Both the V6 and V8 Toro-Flows used balance shafts. All the Toro-Flows were over-square, with the D351 having a bore of 4.56 inches and a stroke of 3.56 inches. All the other engines shared a 5.125-inch bore and 3.86-inch stroke.

The injection system came from American Bosch in the form of the PSJ rotary pump. That’s not one many people remember but it was used on a few engines in that era and is similar to the better-known PSB. It fed Bosch injectors that popped at 3,000 psi. Max full-load rpm was 3,200 for the V6 engines, 2,600 rpm for the D637, and 2,800 for the DH637.

Market Performance and Reliability

There isn’t a whole lot to dislike here, at least on paper: four-bolt mains, a chrome-nickel alloy block, and six bolts per cylinder to tie the head down. With a 950-pound long block assembly weight (D478, the D351 was 10 pounds less), it seems like there was plenty of beef to work with.

However, the Toro-Flow engines are known for two main problems: the American Bosch PSJ injection pump and head gasket failures. The word from back in the day was that regular head re-torquing eliminated most problems relating to head gaskets. The reputed PSJ pump issues are not clear. Various failures are also attributed to continuous hard use and high revving. Overall, Toro-Flows did better in the lighter duty applications than they did in the higher GVW trucks. They fared better in marine applications because those were mostly in pleasure craft. In either case, many parts are incredibly difficult to find, although there seems to be no shortage of remaining engines.

Conclusion

Ultimately, while the Toro-Flow had its shortcomings, it was a practical choice for certain medium-duty applications. It offered a compact design and ease of retrofit, making it a feasible alternative during a period when diesel engines struggled to gain widespread acceptance. Despite its notorious reputation, the Toro-Flow held its ground among its peers, particularly when cost and packaging efficiency were major considerations.

How did the Toro-Flow fit into the medium-duty market compared to other options?

The Toro-Flow was considered a practical choice in the medium-duty market due to its compact size and ease of installation. While not the most powerful or advanced, it offered a balance of cost-effectiveness and utility that made it a viable option against more cumbersome and costly alternatives.

What were the historical market perceptions of diesel engines during the development of the Toro-Flow?

During the development of the Toro-Flow, the market was just beginning to recognize the potential of diesel engines in terms of reliability and longevity. However, the prevailing sentiment was still cautious, as diesel engines had not yet fully proven themselves to surpass gasoline engines in these aspects.

What was the reliability perception of contemporary diesel engines?

Contemporary diesel engines, including options like the Cat 1160 and V8-265 Cummins, often had mixed reliability records. While some engines offered better performance, their higher costs and packaging difficulties, alongside reliability concerns, were significant drawbacks in the medium-duty segment.

How did the Toro-Flow compare in terms of cost and packaging?

The Toro-Flow was engineered to be a cost-effective choice, using similar tooling to GMC’s gas engines, which helped keep production expenses low. Its compact design made it easy to install in medium-duty vehicles, unlike other diesel engines of the time that were more expensive and challenging to fit.

Why were diesel engines a tough sell in the medium-duty market during the era?

Diesel engines faced several challenges in the medium-duty market of the late ’50s and early ’60s. Buyers were hesitant due to issues like difficult cold starts, limited power, scarcity of fueling stations, and higher initial costs. These factors made diesel engines less attractive compared to reliable and well-established gasoline engines.

How did the market’s perception of diesel engines affect the acceptance of the Toro-Flow?

The Toro-Flow’s bad rap was rooted in reality but also needs to be viewed in context. They were some of the first diesels designed and built specifically for the medium-duty truck market of the ’60s, which at the time was a market still dominated by very well-proven gasoline engines. Strange as it sounds, that market was skeptical of diesels and not 100-percent ready for the change to diesel.

During the late ’50s and early ’60s, the medium-duty market was understandably hesitant. Gas engines were a known entity, offering reliability and ease in urban environments. In contrast, diesel engines were still overcoming several hurdles:

• Cranky Cold Starts: Diesel engines of the era often struggled to start in cold weather, causing frustration for users.
• Low Power Output: This was a significant drawback, as the power levels didn’t meet the demands compared to gasoline counterparts.
• Limited Infrastructure: A shortage of diesel fueling stations made it inconvenient for users.
• Lack of Expertise: Mechanics were generally more familiar with gas engines, leaving diesel owners with fewer options for repairs.
• High Initial Costs: The buy-in cost for diesel engines was steep, discouraging potential buyers.

Despite these challenges, diesel engines promised better fuel economy. However, this advantage was frequently overshadowed by their drawbacks. Over time, diesel engines began to match and even surpass gasoline engines in reliability and longevity. Yet, the market’s perception lagged behind these improvements, making it a difficult transition for the Toro-Flow to gain widespread acceptance.

How did users modify or maintain the Toro-Flow engines to improve their performance?

The word from back in the day was that regular head re-torquing eliminated most problems relating to head gaskets. Once this maintenance step was incorporated, many users found a significant improvement in engine reliability. In addition to this, adjusting the RPM was another key factor. Setting engines back to 2800 RPM from an initial 3200 RPM not only enhanced their lifespan but also improved overall performance.

Users learned that these engines weren’t suited for overly heavy trucks and performed best in lighter applications, such as water tankers. This strategic application choice prevented the engines from being lugged too hard, which was a common issue that affected their reputation.

Another crucial maintenance tip was to keep an eye on the oil pump drive gear. It was essential to regularly inspect this component, as it drove off the back of the cam like a gas engine and had a tendency to strip out. Regular checks—at least once a year—helped prevent catastrophic engine failure.

By combining these maintenance practices—head re-torquing, RPM adjustment, suitable application, and vigilant gear inspection—users managed to extend the life and enhance the performance of these engines significantly.

What was the user experience with these engines over the long term?

A fleet owner operated these engines successfully for about 20 years, indicating they could be reliable with proper care and maintenance.

What specific component required regular maintenance to prevent engine failure?

The oil pump drive gear needed regular inspection because it could wear out and lead to engine failure if neglected.

What types of applications were suitable or unsuitable for the engines?

The engines were not ideal for heavy trucks as they did not perform well under heavy loads, but they were effective in lighter vehicles like water tankers.

What RPM adjustments were necessary for better engine performance?

Lowering the RPM from 3200 to 2800 helped improve the engine’s durability and performance.

What were some of the cost-saving measures in the production of the Toro-Flow engines?

The development process for a four-stroke, low-cost diesel began in 1953 and was eventually synchronized with the development of a new 60-degree V6 gasoline engine to be introduced for 1960. This is not to say the diesels would be “converted gas engines.” They weren’t. It’s more accurate to say the gas and diesel V6s were concurrent developments to be built with similar architecture and on similar tooling. There was very little actual parts changeover.

The strategic intent behind this engineering effort was to create a cost-efficient, medium-duty diesel that would fill a gap in the market. At that time, diesel engines were just starting to gain attention from buyers interested in fuel efficiency and lower operational costs. By aligning the diesel engine’s development with that of the V6 gasoline engines, the production process benefited from shared tooling, significantly reducing manufacturing costs.

Moreover, the approach allowed for streamlined production without the need for extensive new infrastructure investments. This design philosophy not only made the diesel engine affordable but also positioned it as a competitive alternative to existing options that were neither economical nor quiet.

In summary, the cost-saving measures were embedded in the engine’s very design and production strategy—leveraging shared architecture and tooling, and aligning with market trends to offer a compelling, budget-conscious product.

What were the development and production strategies for cost savings?

By utilizing the same tooling as the V6 gas engines, the Toro-Flow’s production was made more economical, which contributed to its low-cost positioning.

Was the Toro-Flow a conversion of an existing engine?

The Toro-Flow was not a conversion of the V6 gas engines but was instead designed alongside them, ensuring it was a distinct product built on similar production lines for efficiency.

Why was the timing of the Toro-Flow’s introduction significant?

The engine was launched during a period when diesel engines were beginning to attract interest from consumers in its target market, making its introduction timely and potentially impactful.

How did the Toro-Flow compare to existing diesel options at the time?

Unlike GM’s existing two-stroke diesels, which were costly, less economical, and noisy, the Toro-Flow aimed to improve on these aspects, offering a quieter and more budget-friendly alternative.

What was the intended market position of the Toro-Flow engine?

The Toro-Flow was designed to be an affordable and fuel-efficient option for medium-duty diesel applications, filling a gap in the market that hadn’t been fully addressed.

What was the designation of the rare DH478 turbo road engines used in buses?

The available books don’t show a turbocharged Toro-Flow V8 in trucks, though some unconfirmed sources claim they existed. The Toro-Flow became a relatively popular marine diesel in pleasure craft due to its low cost. Crusader Marine, American Marine, Barr Marine Products, and Daytona Marine offered converted V6 and V8 Toro-Flows. There were twin-turbocharged marine versions that never saw use on the road. A marine DHT478 cranked out 220 hp and the turbocharged DHT637 V8 made 300 hp.

A turbocharged DH478 V6 made the road in the late ’60s GMC bus lines, but finding one is rare. The designation of these rare DH478 turbo road engines used in buses has sparked some debate. While “DHT478” appears in some sources, it’s important to note that this isn’t confirmed by primary sources. This uncertainty adds to the intrigue and rarity surrounding these engines.

Both the on-road and marine versions of the Toro-Flow engines highlight a fascinating chapter in automotive history, underscoring the versatility and adaptability of these power plants across different industries.

Is there any confirmation of the designation from primary sources?

No, the designation “DHT478” was not confirmed by primary sources.

What is the designation of the rare DH478 turbo road engines used in buses?

The designation might be “DHT478,” though this information lacks confirmation from primary sources.

What were some unofficial names and perceptions of the Toro-Flow engines?

The Toro-Flow engines were all narrow 60-degree V-type engines and could be built with both right- and left-hand rotation. Both the V6 and V8 Toro-Flows used balance shafts. All the Toro-Flows were over-square, with the D351 having a bore of 4.56 inches and a stroke of 3.56 inches. All the other engines shared a 5.125-inch bore and 3.86-inch stroke.

The injection system came from American Bosch in the form of the PSJ rotary pump. That’s not one many people remember but it was used on a few engines in that era and is similar to the better-known PSB. It fed Bosch injectors that popped at 3,000 psi. Max full-load rpm was 3,200 for the V6 engines, 2,600 rpm for the D637, and 2,800 for the DH637.

There isn’t a whole lot to dislike here, at least on paper: four-bolt mains, a chrome-nickel alloy block and six bolts per cylinder to tie the head down. With a 950-pound long block assembly weight (D478, the D351 was 10 pounds less), it seems like there was plenty of beef to work with.

Despite these promising specifications, the Toro-Flow engines earned a series of unflattering nicknames, reflecting the mixed perceptions among users. Terms like “Toilet-Flow,” “Trouble-Flow,” “Turdo-Flow,” and “Toro-Flush” were coined by those who encountered frequent mechanical issues. The unofficial moniker “Terrible Flow” further encapsulated the sentiment that these engines were fraught with problems.

The Toro-Flow has a rather notorious reputation and is known for two main problems: the American Bosch PSJ injection pump and head gasket failures. The word from back in the day was that regular head re-torquing eliminated most problems relating to head gaskets. The reputed PSJ pump issues are not clear. Various failures are also attributed to continuous hard use and high revving.

Overall, Toro-Flows did better in the lighter duty applications than they did in the higher GVW trucks. They fared better in marine applications because those were mostly in pleasure craft. In either case, many parts are incredibly difficult to find, although there seems to be no shortage of remaining engines.

These engines, while innovative in some respects, clearly left a divisive legacy, remembered as much for their engineering quirks as for their colorful nicknames.

What community or group holds these perceptions?

The Detroit Diesel Yahoo group is mentioned as a community that holds these negative perceptions of the Toro-Flow engines.

Why might certain communities have had negative perceptions of these engines?

The negative perceptions likely stemmed from the engines being problematic and not meeting expectations, which is reflected in the alternative names given to them.

What are the general perceptions or reputations of the Toro-Flow engines among users or communities familiar with them?

These engines were largely perceived as unsuccessful and problematic, leading to the development of various negative monikers.

What are some of the unofficial or colloquial names given to the Toro-Flow engines?

The Toro-Flow engines were humorously referred to with names like “Toilet-Flow,” “Trouble-Flow,” “Turdo-Flow,” “Toro-Flush,” and “Terrible Flow,” reflecting a less-than-stellar reputation.