Vintage Smoke - Ford 6.9L IDI

Vintage Smoke – Ford 6.9L IDI

1983-87 International/Ford 6.9L IDI

Public and governmental outcry after the oil shortages of the early ‘70s forced U.S. auto, light truck and commercial truck makers towards economical diesel power. Inroads had already been made getting more diesels into the Class 3 through 6 commercial medium trucks, and the higher GVWs had good coverage, but Class 3 and 4 were still often powered by little more than beefed-up passenger car engines. To that time, there wasn’t much incentive to develop diesels for Class 3 and 4 because the thrifty buyers of those trucks, mostly in-city short hoppers, were not keen on the usual 20% price premium. Rising fuel costs changed those attitudes but lower cost diesels were needed to push the idea across the finish line.

01-copy — From 1980, here is one of the prototype 6.9L diesels. Compare it to the1983 image a little farther on. Looking to the right of the picture, you see a strange square corner. This was the Phase 1 oil cooler, which was a complex plate-type design. For production, a more compact tube-bundle style was used. Note also the differences in the upper timing gear cover. At 780 pounds dry and without ancillaries, it was a relatively light diesel.

This is the 1982 International version of the 6.9L, dolled up with chrome and snazzy blue paint. Initially, International had two ratings, 155 horsepower at 3000 rpm and 305 lbs-ft at 1600 rpm or 165 horsepower at 3300 rpm and 310 lbs-ft at 1800, both of those with the early 20.7:1 compression ratio. For ‘84, the common IH ratings were 155 horsepower at 3000 (305 lbs-ft @ 1800) and 165 horses at 3000 with 321 lbs-ft at 1600 rpm. Ratings up to 170 horsepower at 3300 in trucks were allowed. Advertised was a 180 horsepower rating for marine engines. The 6.9L had oil cooled pistons, four-bolt mains, roller tappets, oil cooler, gear driven cam and injection pump, inboard combustion chambers (injectors at top of engine), exhaust valve inserts and positive valve cooling. The crankshaft was a forged unit and the block was cast of nodular iron. The heads were tied down with five bolts for each cylinder.

Fuel economy concerns soon became a factor with Class 1 and 2 light trucks (half to one-ton) as well. Diesels were part of the answer there too but there were few suitable diesels available and the industry addressed it in a short-sighted, haphazard way. Examples of that in the mid-late ‘70s included the 80 hp 3.3L Nissan in International’s Scout SUV and pickup lines, the 100 hp 4.3L Mitsubishi inline in Dodge D/W150-250 trucks and the infamous 120 hp 5.7L Olds diesel in half-ton GM trucks. In the early ‘80s, GM stepped forward a little with the 130 hp 6.2L diesel but you can see the common theme. A high buy-in for the privilege of owning a gutless wonder.

The Ford version of the 6.9L differed in several respects from the International. The secondary fuel filter was mounted on the engine behind the alternator. The primary filter/water separator was mounted on the firewall next to the power brake booster. Also, the Ford had a vacuum pump mounted under the alternator (not shown here) for the vacuum boosted brakes. Ford used a lower profile air filter to fit under the lower pickup hood. Typically, the ‘83 model year Fords were rated at 161 horsepower at 3300 rpm and 307 lbs-ft at 2000 rpm. With the compression boost to 21.5:1, that rating went up to 170 horses and 315 lbs-ft at 1800 rpm. The compression boost to 21.5:1 may have come before the ‘83 Ford model year was over, but we haven’t confirmed that yet. Engine with serial numbers from 59209 and up had the higher ratio and some of those are said to have appeared in 1983 production. We’d like to verify that.

Few knew that International Harvester was working on a new diesel that answered the needs of truck owners from Class 2 through Class 6 (6,000 to 26,000 pound GVW). IH was in the midst of corporate upheavals and red ink but their medium-duty line was a high spot worthy of an investment. A new low-cost diesel was one of those investments. Like most medium-duty lines, the lower GVW end of the IH line was populated with gas V8s, many of those legacy engines from the ‘50s. Beyond the fuel economy angle, they were almost beyond hope of meeting future emissions regulations and being built on tooling that was worn out.

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Target Specifications

The engineering target was for a moderately priced V8 diesel in the 400-450 cubic inch range, making 165 net horsepower at 3200-3500 rpm. After engineering and marketing outlined the basics, execs approved the project in 1977. The serious design work started in March of 1978 with a goal of starting production in March of 1983. The development had a good shortcut, the recently developed medium-duty MV404 and MV446 gas V8s intended to eventually replace the old V-345, V-392 and even older V-478. The new diesel borrowed some of the basic MV architecture and allowed the new diesel to be built on the same new tooling. The proposed 420 cubic inch diesel used the same stroke as the MV-446 but had a smaller 4.00 bore (0.125 inches smaller).

When the suits come to pose, you know it’s a done deal. Here, from left to right, are three VPs; G.D. Aravosis from Marketing, W.A. Wallace from Engineering and V.P Spedale General Manager besides one of the prototype engines. The image accompanied an October 31,1980 press release from the IH Components Group, which incorporated the Indy Engine Plant. The Indy plant had long been IH’s gas engine factory and diesels were built up at Melrose Park, Illinois. As gas engine production slowed, more space was available and diesel production was ramped up at Indy until all the gassers were gone. Indy built all the light and medium-duty diesels for corporate use and those sold to Ford into the 6.4L era. The Indy plant closed in 2009.

In that era, Indirect Injection (IDI) was the easy answer to meeting upcoming diesel emissions requirements and it also delivered better fuel economy than the DI engines of the day. Probably the main reason was low cost, the IDI requiring a much less expensive injection system. In those days, the Ricardo Comet Mark V swirl combustion chamber was the rage. Sir Harry Ricardo had developed the basic design in 1931 and though advances in fuel injection technology would soon tilt the advantage to direct injection, the Ricardo Comet V was a viable answer for the 1980s and was used in many engines of the day.

First Engines

The first prototype engine was completed in August of 1979 and 160 more followed. Early tests highlighted the need for better injectors. The first ones tried were an outward-opening poppet injector that did not deliver anything near the target power level and failed quickly. A temporary breakthrough was achieved by installing a set of two-orifice nozzles from another IH application, getting them through the initial tests and into field testing. It took a while to figure out the right combination of injector, injector targeting, combustion chamber location and compression ratio. The orifice nozzles proved non-optimal from an emissions standpoint, and they were sooting up, so new inward opening pintle injectors were designed and they integrated well with the Stanadyne DB2 rotary pump.

The 6.9L owes it’s basic architecture to the 1975 MV-404 (2 and 4-barrel) and MV-446 (4-barrel) gas engines. No, the 6.9L was not a “gas engine with diesel heads” but the engines shared many features, the same basic dimensions and some parts. New tooling had been built for the MV engines and IH wanted to use it for the 6.9L. The 6.9L and MV-446 crankshafts were nearly identical, though inside sources tell us the heat treating was different. The MV engines had two-bolt mains and the diesel had four-bolt. Both the gas and diesels used the same gear drives for the cam and oil pump. The MV heads were tied down with four bolts per cylinder and the 6.9L with five. The rocker gear is similar as were the valve covers. The MV series engines had a relatively short life, just seven years (1975-81) to the tune of 120661 404 and 446 engines. This is also a dressed-up show engine. Normally, they were painted red.

A total of 21,000 dyno test hours were accumulated at 3300 rpm, full load, peak power and some 52,000 test hours total. Starting in September of 1980, prototype engines were installed into trucks and field tested, with over 813,000 test miles accumulated. Once all the bugs were discovered and dealt with, they built 10 preproduction engines on the new line and some were tested a further 1,000 hours at full power on the dyno and then out in the field. Actual production started in August of 1982, beating the original timeline estimate by seven months.

Enter Ford

Once the concept was proven and testing well underway, IH began actively shopping the engine around. International wasn’t interested in supplying other medium-duty manufacturers but light-duty was another matter since they had discontinued their own light line by then. Ford Motor Company was on the hook almost from the start. Being only slightly larger and heavier than their existing 460 bigblock V8, it was a sure fit in Ford light trucks. Ford opted to offer it only in light trucks with an 8,500 pound GVW, or more, meaning F250HD and F350 models. That included the Ford E250 and E350 vans but not Ford’s medium-duties. It began a business relationship that lasted 30 years, though it ended badly.

The ‘84-87 Ford sea level and high altitude power graphs show a flat torque curve from idle to about 1800 rpm. The 1400-1800 rpm range is the sweet spot for these engines.

Ford started installing 6.9L engines in August of 1982, first at the Twin Cities Assembly Plant and at all the relevant truck plants shortly thereafter. Until about March of 1983, you could only get it with a manual trans until the tooling was ready to mount the C-6 behind it. Ford advertised 161 horsepower at 3300 rpm and 307 lbs-ft at 2000 with a 19.7:1 compression ratio. These specs come from Ford Data Books, brochures and Ford Facts Books dated August and September of 1982. The early magazine tests listed these specs as well. International documents from the same era show the engine with a 20.7:1 compression ratio and it’s very likely the 19.7:1 ratio listed is either a preliminary number that was changed or incorrect. As it was, the 20.7:1 ratio delivered cold starting issues and it was increased to 21.5:1 for 1984 with piston and cylinder head changes.

Impact on History

In the medium-duty market, the 6.9L added an entry-level diesel into International’s 1600, 1700 and 1800 lines, both busses and trucks, with GVWs up to 26,000 pounds. That was good for International’s bottom line but it didn’t rock the medium-duty world and other manufacturers followed suit with similar engines. It sounded the death knell International’s medium-duty gas engines, including the relatively new MV series. Production of gassers at IH (later Navistar) dwindled into the hundreds of engines by the mid ‘80s and had ended completely by 1988.

The lower end is very stout for the era. Shown is a 1986 engine during an overhaul. You can see the four-bolt mains and gear drives.

The 6.9L was replaced by the 7.3L IDI in 1988, which acquired turbocharging in it’s final year of production, 1994. A total of 436,868 6.9L engine were built from August of 1982 to August of 1987. The HEUI diesel emerged in ‘94, called the T444E by International, and Powerstroke by Ford. By then, International Harvester had been broken up. The Motor Truck Division, including the engine manufacturing component, became Navistar International.

The weakest link of the 6.9L are the head gaskets and head bolts. Modern head gaskets with an ARP head stud kit cures this weakness.

The 6.9L had more significance in the light-duty market and talking about it forces us to risk inciting GM versus Ford rivalry. GM beat Ford to the punch with the intro of the 6.2L diesel for 1982. It was a far better engine than the 5.7L it replaced but was still low on power. The 1982 6.2L GM diesel emerged with 130 horses and 240 lbs-ft. (135 hp in HD emissions) and stayed at those ratings until later in the ‘80s. The 6.9L emerged for ‘83 at 161 horsepower and 307 lbs-ft but was up to 170 horses and 315 lbs-ft by 1984. The 6.2L was available in all GM trucks into the C/K 30 realm and did pretty well in the half-ton lines. It was less stellar mounted in hard-working 3/4 and 1-tons where low power delivered mediocre loaded performance and some significant degradation in reliability.

Two 1986 Ford F-250HDs. Left: What was done. Right: What Gale Banks did and Ford/Navistar should have done to rock the world. Banks came out with a non-wastegated turbocharger kit for the 6.9L in 1984. It made about 10 psi boost, and Banks advertised 255 horsepower and 550 lbs-ft. The first generation kit on the right was installed by the original owner when the truck had 7,000 miles. It’s still there and can still put 200 horses to the rear wheels.

The buy-in was still pretty high for both engines (vs a big block which was around a $500 for both FOrd and GM) so recovering those costs from fuel and maintenance savings could take a while. The 1983 GM 6.2L diesel option was $2375 ($1334 engine plus $1041 for the required diesel equipment package). For ‘83, the complete Ford 6.9L option at $2225 for the 4×4 and $2543 for the 4×2. Considering the power difference, which was the better deal? Not to disparage the 6.2L, but in looking back, and using boxing metaphors, you could say the 6.2L was a lightweight or welterweight in it’s output and construction. The 6.9L was a solid middleweight or maybe a light heavyweight. The GM 6.2L was a good and economical choice in a half-ton but if you towed or hauled, the Ford 6.9L was the better choice. Today, most would sneer at a 170 hp NA diesel with 315 lbs-ft, but in the early ‘80s those numbers gave you some braggin’ rights.

FREQUENTLY ASKED QUESTIONS

What are the typical wear items to check on a 6.9l IDI diesel engine?

Typical Wear Items on a 6.9L IDI Diesel Engine

When maintaining a 6.9L IDI diesel engine, several components tend to wear out over time and should be checked regularly to ensure optimal performance.

Injection Pumps
These are crucial for the engine’s performance, typically lasting anywhere from 100,000 to 150,000 miles. If you notice any decline in fuel efficiency or power, it might be time to consider re-manufacturing the injection pump, which could cost around $500.
Glow Plugs
Essential for cold weather starting, glow plugs can deteriorate over time. It’s advisable to use high-quality glow plugs, as cheaper alternatives may swell, become stuck, or even break off, causing serious damage to the engine. Consider installing them with a push-button system to enhance durability and reliability.
Fuel Filters
Regularly replace fuel filters to prevent contaminants from affecting engine performance. Clogged filters can lead to reduced power and efficiency.
Belts and Hoses
Inspect belts and hoses for any signs of wear, cracks, or leaks. Over time, these components can degrade, leading to potential engine overheating or failure.
Battery and Electrical System
Ensure the battery and electrical systems are functioning well, as poor connections or a weak battery can cause starting issues.

By keeping a close eye on these wear items, you can help extend the life of your 6.9L IDI diesel engine and maintain its performance over time. Regular maintenance and timely replacements are key to avoiding costly repairs down the road.

What is the typical fuel efficiency (mpg) of the 6.9l IDI diesel engine?

When evaluating the typical fuel efficiency of a 6.9L IDI diesel engine, you can expect varying performance depending on the load and terrain. For towing scenarios, this engine often delivers around 11 miles per gallon (mpg). On the other hand, when not towing and driving under normal conditions, the fuel economy can improve significantly, reaching between 16 to 18 mpg.

It’s important to note that while this engine generally performs well in most situations, challenges can arise on onramps and steep inclines. The diesel’s limited RPM range can necessitate downshifting to maintain speed, sometimes to third gear at speeds as low as 45-50 mph. This can affect fuel efficiency and momentum, especially when climbing.

For those using an automatic transmission, you might see consistent fuel mileage of around 16-17 mpg when the vehicle is unladen. Adjustments in driving habits and road conditions can influence these figures, but these estimates provide a baseline for understanding what to expect from a 6.9L IDI diesel engine’s fuel consumption.

What are the differences between the 6.9l IDI and the 7.3 IDI engines?

When comparing the 6.9L IDI and the 7.3L IDI engines, several key differences stand out. While both are part of the International Harvester’s line of indirect injection (IDI) diesel engines, they have distinct characteristics and applications.

Engine Displacement

6.9L IDI: As its name suggests, this engine has a displacement of 6.9 liters. It features a smaller bore compared to the 7.3L version.
7.3L IDI: This engine boasts a larger 7.3-liter displacement, derived from increasing the bore size of the 6.9L.

Power and Performance

6.9L IDI: Recognized for its reliability, it’s favored when running high boost levels, as the smaller bore can handle stress effectively.
7.3L IDI: Generally, this engine provides more power than the 6.9L due to its increased displacement, which makes it a better choice if higher power output is desired without modifications.

Boost Handling

6.9L IDI: Its smaller bore makes it preferable for applications with elevated boost, as it performs well under pressure.
7.3L IDI: Though capable, it is less optimized for high boost conditions compared to the 6.9L due to the larger bore.

Application Preference

For users focusing on power and performance without extensive modifications, the 7.3L IDI stands out. However, if stress management under high boost is a priority, the 6.9L IDI would be advantageous.

In summary, the choice between a 6.9L and a 7.3L IDI often depends on the specific needs of performance, reliability, and how much boost the engine is expected to handle.

What are the benefits of manual transmission over automatic for the 6.9l IDI diesel engine?

Benefits of a Manual Transmission for the 6.9L IDI Diesel Engine

The choice between a manual and automatic transmission can significantly impact your driving experience, especially with a robust engine like the 6.9L IDI diesel. Here’s why opting for a manual transmission might be advantageous:

Enhanced Control and Performance

Precision in Gear Selection: A manual transmission allows you to choose the gear that best suits your driving conditions, giving you greater control over the engine’s power. This can be particularly useful when towing heavy loads or navigating challenging terrain.
Improved Fuel Efficiency: By manually selecting gears, you can optimize fuel consumption based on your driving habits and conditions. This efficiency can lead to cost savings over time, which is an important consideration for diesel engines.

Mechanics and Maintenance

Simplicity and Longevity: Manual transmissions are mechanically simpler than their automatic counterparts. They often require less maintenance and tend to have a longer lifespan, which can be beneficial for the durability-focused design of the 6.9L IDI.
Cooling Advantage: Manuals are less prone to overheating compared to automatics, which often require additional components like transmission fluid coolers. This stability under stress makes manuals ideal for heavy-duty and long-distance driving.

Driving Experience

Engaging Drive: Many drivers appreciate the more involved experience of driving a manual. The connection between the driver, vehicle, and road can lead to a more enjoyable journey, turning every trip into an engaging experience.
Cost-Effectiveness: Generally, manual transmissions are more budget-friendly both in terms of initial purchase and potential repairs. The investment can be particularly wise for those keen on maximizing value without sacrificing performance capabilities.

In summary, choosing a manual transmission for your 6.9L IDI diesel engine enhances control, efficiency, and longevity, making it a compelling option for those who value both performance and practicality.

How do the 6.9l IDI diesel engines perform with alternative fuels like waste motor oil or waste vegetable oil?

Performance of 6.9L IDI Diesel Engines with Alternative Fuels

The 6.9L IDI diesel engines are increasingly recognized in the alternative fuels community for their adaptability and robust performance. If you’re considering using these engines with alternative fuels like waste motor oil or waste vegetable oil, here’s what you need to know:

Versatility with Alternative Fuels: These engines handle a variety of fuels excellently. Waste motor oil and waste vegetable oil are popular choices, thanks to their accessibility and cost-effectiveness. By making minor modifications, the engine can efficiently process these alternative fuels, reducing your dependency on traditional diesel.
Performance Insights: A turbocharger kit can significantly boost the engine’s output. Although their indirect injection design doesn’t allow for the same high boost pressures as direct injection engines, a turbo can still revitalize the engine, increasing power and efficiency.
Adaptations Needed: To run smoothly on waste oils, the engine typically requires some adaptations. You may need to install additional filtration systems to handle impurities and adjust the fuel lines to accommodate the different viscosity levels of alternative fuels.

In conclusion, the 6.9L IDI diesel engines prove to be a formidable choice for anyone interested in alternative fuel options, offering credible performance and the opportunity for efficiency gains with suitable modifications.

What should be considered when purchasing a used 1985 F350 with a 6.9l IDI diesel engine?

What to Consider When Buying a Used 1985 F350 with a 6.9L IDI Diesel Engine

Glow Plugs
One of the key components to keep an eye on is the glow plugs. They need to be replaced periodically, as they tend to wear out over time. Using high-quality glow plugs is crucial; cheaper options may swell or break apart in the cylinders.

Transmission Types
Consider whether the truck has a manual or automatic transmission. A manual transmission often enhances performance. If it’s equipped with a 4.10 rear gear ratio, expect higher RPMs at highway speeds, especially with an automatic transmission.

Odometer and Mileage
These trucks come with 5-digit odometers, which don’t reveal the full mileage if it’s rolled over. However, mileage isn’t always a significant issue if the vehicle has been well-maintained.

Fuel System
Be aware of potential air intrusion in the fuel system, a common issue that can sideline the truck. Fortunately, you can resolve this by replacing the return lines, which is a straightforward fix.

Injection Pump and Maintenance Costs
Watch out for the injection pump, a critical component that typically lasts 100,000 to 150,000 miles. Rebuilding or replacing it can cost around $500. Knowing the condition of this part can save you from unexpected expenses.

Starting System
For quick and reliable starts, ensure the truck has two good batteries and quality cables. Many of these vehicles have been retrofitted with a pushbutton starter, bypassing the likely worn-out stock glow plug timer.

Engine and Cooling
Although some owners report issues with head gaskets and coolant consumption, these problems aren’t universal. Regular checks and maintenance can prolong the engine’s life and performance.

By considering these aspects, you’ll be better prepared when purchasing a used 1985 F350 with a 6.9L IDI diesel engine.

What modifications can improve the power and efficiency of a 6.9l IDI diesel engine?

Two 1986 Ford F-250HDs. Left: What was done. Right: What Gale Banks did and Ford/Navistar should have done to rock the world. Banks came out with a non-wastegated turbocharger kit for the 6.9L in 1984. It made about 10 psi boost, and Banks advertised 255 horsepower and 550 lbs-ft. The first generation kit on the right was installed by the original owner when the truck had 7,000 miles. It’s still there and can still put 200 horses to the rear wheels.

To enhance the power and efficiency of a 6.9L IDI diesel engine further, consider making some precise adjustments:

Fuel Adjustment: Turning up the fuel can provide a noticeable boost in power. This modification increases the amount of fuel injected, leading to more energy output.
Timing Optimization: Nudging the timing can also improve engine performance. Adjusting the timing ensures that the fuel is ignited at the optimal moment, maximizing efficiency and power.
Monitoring with a Pyrometer: It is crucial to have a pyrometer installed. This device monitors exhaust gas temperatures, allowing you to keep an eye on potential overheating issues that could arise from these modifications.

These steps, paired with the turbocharger kit, offer a comprehensive approach to unleashing the full potential of your diesel engine, ensuring not just power, but also a reliable and efficient performance.

What precautions should be taken when modifying the engine?

It’s crucial to use a pyrometer to monitor the engine to ensure that the modifications do not lead to overheating or damage.

What specific modifications can be done to improve performance?

Adjusting the fuel levels and tweaking the timing can significantly enhance engine performance.

What are common problems or repairs needed for the 6.9l IDI diesel engine?

The weakest link of the 6.9L are the head gaskets and head bolts. Modern head gaskets with an ARP head stud kit cures this weakness. However, there are other aspects to consider for a well-rounded understanding of maintenance needs for this engine.

Glow Plugs are a common area of attention. Over time, they can become slower and produce more smoke, eventually failing. It’s advisable to install high-quality glow plugs to prevent issues such as swelling or breaking, which can lead to further engine damage.

Fuel System Issues, particularly air intrusion, can sideline the engine. Addressing this involves redoing the return lines to ensure they are airtight, which is a relatively straightforward fix.

Injection Pumps are notable wear items, typically lasting between 100,000 to 150,000 miles. When replacement is necessary, a remanufactured pump can cost around $500.

Starting System reliability hinges on having two robust batteries and good cables. This ensures the engine starts quickly and reliably, especially if the original glow plug timer has been replaced by a pushbutton system.

While some owners report problems with head gaskets and water usage, many have not experienced these issues extensively. Nonetheless, being aware of these potential areas can help in maintaining the longevity and efficiency of the 6.9L IDI diesel engine.

What are potential issues with head gaskets and water usage?

Some owners report problems with head gaskets and excessive water usage. However, not everyone experiences these issues, suggesting variability in how these components perform across different engines.

What considerations are there for starting the engine reliably?

To ensure reliable starting, it’s crucial to have two high-quality batteries and robust cables. Additionally, the stock glow plug timer might be unreliable, so switching to a pushbutton system could be beneficial.

What is the lifespan and cost of injection pumps?

Injection pumps typically last between 100,000 and 150,000 miles. If they need replacement, a remanufactured unit generally costs around $500.

What is a common issue related to the fuel system?

A frequent problem in the fuel system is air intrusion. This can often be resolved by redoing the return lines, which is a relatively straightforward fix.

What are the signs that glow plugs need to be replaced?

Glow plugs should be replaced when they cause the engine to start slower and produce more smoke. These are key indicators that the glow plugs are becoming ineffective and may soon fail.

How does altitude affect the performance of the 6.9l IDI diesel engine?

The ‘84-87 Ford sea level and high altitude power graphs show a flat torque curve from idle to about 1800 rpm. The 1400-1800 rpm range is the sweet spot for these engines.

However, when you take these 6.9L IDI diesel engines to higher altitudes, such as the Rockies, you might notice a significant change in performance. At elevation, the engines tend to become seriously smokey, a phenomenon known as “rolling coal.” This increase in smoke can indicate less efficient combustion due to the thinner air, which can cause issues not only with performance but also with emissions compliance.

To address these challenges, one potential modification is the addition of a turbocharger. A turbo can help improve air intake, thus enhancing combustion efficiency, even in high-altitude environments. This modification can help maintain the engine’s performance and reduce excess smoke, keeping it running smoothly regardless of elevation.

What are the legal or regulatory considerations when operating this engine at high altitudes?

Operating the engine at high altitudes with increased smoke emissions could lead to legal issues, such as receiving a ticket for excessive smoke output, often referred to as “rolling coal.” It’s important to be aware of local regulations regarding vehicle emissions.

Are there any modifications recommended to improve engine performance at high altitudes?

To enhance performance at elevation, adding a turbocharger is suggested. This modification can help the engine maintain power and efficiency in thin air conditions.

How does altitude affect emissions or visibility when using the 6.9L IDI diesel engine?

At high altitudes, the 6.9L IDI diesel engine may produce more smoke, which can lead to visible emissions that might be concerning from an environmental or regulatory standpoint.

How well does the 6.9l IDI diesel engine tow?

“Today, most would sneer at a 170 hp NA diesel with 315 lbs-ft, but in the early ‘80s those numbers gave you some braggin’ rights.”

Yet, the true strength of the 6.9L IDI engine lies beyond mere numbers—it’s in the way it tows. While a modern truck, like an early 2000’s 5.3 Silverado, might outpace it in a sprint, towing isn’t just about speed. The IDI engine is built for endurance, effortlessly handling the load without constant gear shifts, unlike the Silverado that might find itself dropping to second gear and revving up to 4500 RPM frequently.

Here’s how to make the most of your IDI engine for towing:

Keep it wound up: The engine performs best when kept at higher RPMs.
Adjust the fuel and timing: A slight increase in fuel and timing adjustments can yield noticeable improvements in towing performance.
Monitor with a pyrometer: This is essential for keeping an eye on exhaust gas temperatures and ensuring the engine operates within safe limits.

With these adjustments, the 6.9L IDI doesn’t just tow well—it does so with a reliability that endures for decades, making it a stalwart choice for those who value long-term performance over quick bursts of power.

What is the key to effective towing with an IDI engine?

Maintaining higher engine RPMs is crucial for effective towing with the IDI engine, as it helps in delivering consistent power and performance.

What equipment is necessary for safe towing with the 6.9L IDI?

It’s essential to use a pyrometer to keep track of the exhaust gas temperature, ensuring the engine stays within safe operating limits during towing.

What specific modifications can enhance the towing performance of the 6.9L IDI?

To boost towing power, adjustments such as increasing the fuel quantity and fine-tuning the timing can significantly enhance the engine’s performance.

What are the operational characteristics of the 6.9L IDI when towing?

The 6.9L IDI diesel engine operates steadily at around 2800 RPM during towing, minimizing the need for frequent gear changes and providing a reliable towing experience.

How does the towing performance of the 6.9L IDI compare to another engine?

When comparing the 6.9L IDI diesel engine to an early 2000’s 5.3L Silverado, the Silverado has the upper hand in terms of speed and acceleration with a trailer. However, the IDI engine excels in longevity and consistent performance over time.

What maintenance issues are common with the 6.9l IDI diesel engines?

The weakest link of the 6.9L are the head gaskets and head bolts. Modern head gaskets with an ARP head stud kit cures this weakness. However, maintaining these engines involves more than just addressing head gasket issues.

Glow plugs are another critical component. Over time, they can slow down and produce more smoke, signaling the need for replacement. Opt for high-quality glow plugs and consider using a pushbutton to ensure reliable performance. The original glow plug timers often fail, so upgrading to a manual system is a common practice.

Air intrusion into the fuel system is a frequent problem, leading to performance issues. Regularly redoing the return lines can prevent this, keeping your engine running smoothly. Injection pumps are another significant wear item, typically lasting between 100,000 to 150,000 miles before needing a remanufacture, which can cost around $500.

To ensure quick and reliable starts, invest in two good batteries and quality cables. Although some owners report concerns about head gaskets and coolant usage, these issues can often be managed with proper maintenance and upgrades.

By addressing these common maintenance areas, you can extend the life and reliability of your 6.9L IDI diesel engine.

What are the electrical requirements for reliable starting?

To ensure the engine starts quickly and reliably, two high-quality batteries and robust cables are essential.

What is the best approach to replacing glow plugs?

It’s advisable to use Motorcraft glow plugs and install them on a pushbutton system to prevent swelling and prevent tips from dropping into the cylinders.

What maintenance is required for the injection pump?

The injection pump typically lasts between 100,000 to 150,000 miles, and remanufacturing it costs approximately $500.

What are the potential issues with the fuel system?

Air intrusion is a notable issue within the fuel system, but this can be addressed by redoing all the return lines.

What are common symptoms of aging glow plugs in the 6.9L IDI engines?

As glow plugs age, the engine tends to become slower in performance and emits more smoke until the glow plugs eventually fail.

How does the 6.9l IDI diesel engine compare to modern engines in terms of power and speed?

“Today, most would sneer at a 170 hp NA diesel with 315 lb-ft, but in the early ‘80s those numbers gave you some braggin’ rights.”

Back then, the 6.9l IDI diesel engine was a workhorse, known for its steadfast reliability rather than blistering speed. While it doesn’t compete with the high-speed capabilities of modern engines, it has its own unique charm and advantages.

On the Road: When tackling hills, this engine thrives on patience. You might not be the first to reach the summit, but by following behind big rigs with your 4-way flashers on, you’ll always get there. The key is to feed it as much fuel as it can handle without smoking.
Towing Capability: It’ll tow nearly anything—but don’t expect to do so at 70 mph. Instead, it prefers a steady pace, offering a sense of security and longevity in its performance.
Comparative Power: To put it in perspective, if you hooked up the same car trailer to this engine and a contemporary 5.3-liter gasoline engine, the latter would likely outpace it. Yet, where the 6.9l IDI shines is in its ability to perform consistently over decades, cruising comfortably at lower RPMs.
Driving Experience: Driving an N/A diesel can feel like having the parking brake engaged. It’s not about rapid acceleration; it’s about a steady, unyielding journey.

In a world obsessed with horsepower and speed, the 6.9l IDI diesel serves as a reminder that sometimes, endurance and reliability are the true measures of an engine’s worth.

What are the benefits of this engine in terms of longevity?**

The engine is designed for endurance. It can perform effectively over decades, maintaining a low RPM range that reduces wear, unlike some modern engines that might stress their components with higher RPMs during towing.

What are the trade-offs between this engine and modern engines?**

While modern engines may provide higher speeds and power, they often require more frequent gear shifts under load. The 6.9 IDI, in contrast, focuses on durability and steady operation, even if it’s not the fastest option.

What is the driving experience like with this engine?**

Driving this engine can feel somewhat sluggish, akin to having the parking brake engaged. It may lack the responsiveness and quick acceleration of newer engines.

How does it compare to a modern engine in terms of towing capability?**

Compared to a modern engine like an early 2000’s Silverado, the 6.9 IDI might not match in speed or acceleration. However, it offers reliable, consistent performance over time without the need for frequent gear changes.

How does the engine perform under load?**

The engine requires you to reduce speed and optimize fuel intake to prevent issues like smoking when tackling hills. It’s capable of towing heavy loads, but does so at more manageable, slower speeds.

How reliable are the 6.9l IDI diesel engines?

The weakest link of the 6.9L are the head gaskets and head bolts. Modern head gaskets with an ARP head stud kit cures this weakness. Beyond this, these engines are known for their robust performance and durability. They might not be the fastest on the road, but they are built to last and handle heavy-duty tasks with ease.

For those interested in alternative fuels, the 6.9L IDI is a popular choice, capable of running on waste motor oil and veggie oil. While turbo kits can enhance performance, it’s important to remember that these engines operate best at lower boost pressures compared to direct-injected counterparts.

However, be aware of some common maintenance needs. Air intrusion into the fuel system is a frequent issue, easily addressed by redoing the return lines. Injection pumps typically require replacement every 100,000 to 150,000 miles, with remanufactured options available around $500. Also, consider upgrading to high-quality glow plugs, like those from Motorcraft, to prevent swelling or tip damage.

A manual transmission can improve drivability, though many units come with a C6 automatic. Pay attention to the rear gear ratio, especially if it’s a 4.10, as this can push the engine near its limits at highway speeds.

Finally, ensure you have two good batteries and quality cables to guarantee reliable starts. Despite some concerns about head gaskets and water usage, many owners find these engines to be exceptionally dependable over the long haul.

What are the important maintenance tips for ensuring reliability?

To maintain reliability, it is advised to use high-quality glow plugs and maintain good battery health. Checking the rear gear ratio, especially if it’s 4.10, is crucial to avoid running near the governor at highway speeds.

What are the common issues and how can they be resolved?

A frequent problem is air intrusion in the fuel system, which can be resolved by redoing the return lines. Another issue involves the injection pumps, which typically last between 100,000 to 150,000 miles and cost about $500 to rebuild.

What are some practical experiences and real-world mileage with these engines?

Owners have reported driving these trucks for over 100,000 miles without major issues, showcasing their long-term reliability and robustness.

What is the overall performance and efficiency of the engine?

The 6.9L IDI is known for being slow but notably efficient for a full-size truck. It’s designed to handle heavy work, albeit at a leisurely pace, emphasizing durability over speed.

What are the common uses and modifications for the 6.9L IDI engines?

These engines are popular in the alternative fuels community, frequently used with waste motor oil and veggie oil. Turbo kits are also available to enhance performance, even though they require lower boost pressures compared to direct-injected engines.