Cummins Big Cam 400 Max HP (400 Big Cam Cummins Specs)

The price tag for this top Cummins engine rivals the price tag of fully constructed small cars. But when you want a top engine under the hood, you should expect to pay more. This engine can survive up to 600 HP but only in rare instances.

The Cummins Big Can engine is powerful as its stated top HP is 450 but there will be times when you will produce more HP than the stated high. Its best application is for marine work but that shouldn’t stop you from placing this cheaper engine in your rig.

To learn more about this engine and its specs, just continue to read our article. It has the information you want to know about so you can make the important decision if this motor is right for you and your towing, etc., situation.

How Much Horsepower Does a 400 Big Cam Cummins Have?


This will depend on which model of Big Cam you are talking about. The old 855 Big Cam that was introduced in 1976 reached a high of 605 HP at 1800 RPM.

The Big Cam 400 has been said to reach 450 HP but it does not have the fuel efficiency other engines may have. The problem is this is a very old engine. Not as old as the 855 but old enough.

It was said to be released around 1982 and that is 40 years of hard labor. There have been several versions of the Big Cam 400, #1, 2, 3 & 4 and the #3 version was said to get 400 HP.

It is also said that the #4 version is not the best of the lot. It had some problems that took away its power and fuel efficiency. There is more praise for the Big Cam 855 motor and at least one repair company has said if you haven’t driven a vehicle with this engine in it, you are missing out.

Cummins Big Cam 400 Max Hp

Depending on the version of the engine you own, you can expect anywhere between 400 and 450 HP. That may be the best you will get unless you fine-tune it yourself and add a few more parts to it.

There is one YouTube video out there proclaiming that they were able to tune this engine to reach 700 HP. We did not watch the video so we can’t be sure what they did to reach that level.

Other owners have stated that they heard the engine was able to get to 600 HP stock but that was in a runaway situation. It is best to not try to get to those levels at any time under normal driving conditions. These motors may be old but they are still not cheap to buy or refurbish.

There are refurbished engines on the market and the selling price is almost $20,000. That tells you that the replacement parts are not going to be cheap either. The durability of the Big Cam 400 is not that high either so be careful and take good care of it if you own one.

Complete 400 Big Cam Cummins specs

Manufacturer - Cummins Engine Company, Inc.

Model - NTC-400

Type - 4-cycle, turbocharged diesel, compression ignition


Length - 58.88 in. (149.6 cm)

Width- 33.63 in. (85.4 cm)

Height- 50.91 in. (129.3 cm)

Net Weight, Dry- 2,600 lbs (1,180.4 kg)


Number - 6

Arrangement - In-line

Firing Order- 1-5-3-6-2-4

Bore - 5.5 in. (14 cm)

Stroke - 6 in. (15.2 cm)

Displacement - 855 cu-in. (14 L)

Compression Ratio- 13.5:1 (M915/Big Cam I) 14.0:1 (M915A1/Big Cam III)


Full Load- 2100 rpm

No Load- 2460 rpm

Idle Speed- 600 rpm


Type- Force-fed

Operating Pressure (Normal) - 35-45 psi (M915A1/Big Cam III)

50-70 psi (345-483 kPa) (M915/Big Cam I)

Operating Pressure (Minimum)- 15 psi (100 kPa) @ idle

System Capacity Including Bypass Filter - 44 qt (41.6 L) (M915A1)

46 qt (43.5 L) (M915)

Operating Temperature (Normal) - 200-250°F (93-121°C)

Oil Pump- Gear-type


Type- Liquid with fan and radiator

Operating Temperature (Normal)- 175-195°F (79-91°C)

Thermostat- 1


Maximum Torque- 1150 lb-ft @ 1500 rpm (M915/Big

Cam I)

1300 lb-ft @ 1300 rpm

(M915A1/Big Cam III)

Maximum Output - 400 BHP

Piston Speed @ 2100 rpm 2100 ft/min

{The source for these specs is found at this link}

What Liter is a 400 Big Cam Cummins?


The specs above and other sources confirm that this engine reached 14 liters. However, we have seen other websites stating that this engine only reached 8.9 liters. We do not give much credence to the latter number.

14 liters seems to be the standard most experts have reported. One of the drawbacks to this size of the engine was that it liked to smoke a lot. If you start it up inside a garage you want to get it outside as soon as possible as the garage will be filled with exhaust quickly.

This engine would also pump raw fuel out of the stacks until it reached its 160-degree F operating temperature. This is one of those engines that did not have to meet strict EPA regulations.

Getting to its operating temperature takes about 10 to 15 minutes depending on the temperature outside. As far as we can tell, there was not a wide range of changes made between the Big Cam 3 and 4 engines. It may still smoke a lot when just getting started.

Big Cam 400 Cummins Torque

According to the specs above, you should be seeing this torque range: Maximum Torque -1150 lb-ft @ 1500 rpm (M915/Big Cam I)

1300 lb-ft @ 1300 rpm (M915A1/Big Cam III)

Maximum Output- Piston Speed @ 2100 rpm 2100 ft/mi

That is still fairly powerful for an engine as old as this one. The torque figures you receive may be slightly different depending on the version of the Big Cam 400 you own. Plus, it will depend a lot on the type of maintenance the motor received over the years.

Another source reported a maximum torque: Up to 1,118 lb-ft. That will [prove that what you get may differ from what other people get. As we said it will all depend on several factors including the condition of the engine.

If you want expert advice on the torque for this engine, you need to contact the people at Pittsburgh Power. They seem to be the experts on this engine and have over 150 years of combined work experience.

It is said that they know how to tune up an older engine and get more HP out of it than anyone else.

400 Big Cam Cummins Fuel Mileage

If anyone reports that they got double-digit MPG then you know they are lying. They may want to sound impressive but their reporting is not factual. The real figures are much lower than double digits.

The owners who are reporting their fuel mileage are saying they are lucky to get above 6 mpg and usually they are down around 4 to 5 mpg. That sounds more realistic than double digits.

Of course, if you are driving a lot in the city, then you can expect to be on the lower end of that range. Maybe just over 4 mpg will be close to what you would get.

One owner is reporting he is getting between 6.6 and 7.8 mpg but he also encounters a lot of wind and he may have wind power help or wind resistance depending on his direction.

Also, if you are driving a lot of hills expect to get less than 4 mpg per trip. The driving conditions and geography will play a large role in your totals. Rarely are the driving conditions ideal and you may be spending a lot of money on fuel, especially with today’s fuel prices.

400 Big Cam Cummins Weight

According to the specs above, you are looking at an engine that weighs more than a ton. The dry weight of this engine is 2600 pounds and dry weight means without all the liquids inside.

Expect to reach close to 2800 to 3000 pounds when all the liquids have been added to this motor. This weight should keep your top speed from reaching very high figures.

One owner reported seeing only 72 mph as his top speed. But that is just one model of the 400 and one configuration. Other owners have reported getting a top speed of over 100 mph but they said their engine was coupled with a 13-speed transmission and 3.73 rear end.

Your top speed will depend on several factors especially if you are going down a steep grade. Some owners are reporting only receiving a top speed of 70 mph with a 4.11 rear. The ratio will play a large role in how fast you can go at any time as well.

400 Big Cam Cummins Years Made


The closest we can pin this engine’s production years is the 70s and the 80s of the last century. Since there have been production changes to the Big Cam 400 you may see some as young as the 1990s and as old as 1975.

The N14 was supposed to be its replacement and the early production years were the late 1980s and released to the public somewhere around 1991. All figures are approximations.

This production era means that fuel efficiency as well as environmental regulations were not at their strongest levels. This was an engine that used a lot of fuel and spewed a lot of exhaust when getting up to its operating temperature.

Plus, it was not a very durable engine compared to the N14. But many owners liked the way it pulled and felt it had a lot of power for an older engine. The recommendation is that this motor is best used in marine applications.

But if it is in your truck, you have a very good engine under the hood.

The Price For a Refurbished Big Cam 400

Even though it is old, this engine still retains a lot of value. For some models for sale, the companies that own them and may have rebuilt them are saying to contact them for their price.

That is understandable as they do not want to scare away customers. But to give you an idea of their overall cost used, we have seen these refurbished engines sell for as low as $3600 to $7400 to $16,000 and almost $20,000.

Most of the engines for sale currently at one location are the Big Cam 3 motors. There is some good news in all of this though. Some used engines are selling for as low as $2500 to $3500.

The price will depend on the condition and what has been done to it.

Where To Find a 400 Big Cam For Sale


One location will be the My Little Salesman website. They seem to be just a listing agency and trying to connect potential customers with sellers. Another place is called Machinio and they seem to be selling the vehicle with the engine installed.

Their prices will range between a few hundred dollars to close to $30,000 depending on if you want parts or a whole truck with the engine. Other locations seem to be engine-rebuilding shops that have made a substantial investment in rebuilding these top engines.

A quick internet search should turn up some near you.

Some Additional Words

This Big Cam 400 seems to come with a lot of praise. It is one of the better engines made and rivals its competitors in power and more. Many people like the engine and have given it high marks.

If taken care of properly it should have a long lifespan. But do not be surprised if they have been rebuilt by now. They are very old engines and their parts are wearing out.

When you are going used, a good Cummins engine like the Big Cam 400 series is a good place to start.

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