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Old 12-01-2009, 12:56 PM   #1
JET4x4
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2001 8.1L issues

I'm looking into buying a 2001 chevy crew cab with the 8.1 big block and an allison trans. The truck has 121,000 miles on it. I was just wondering about the durability of this engine and if there are any known issues. Also what kind of gas mileage can I expect? I'm guessing 11 mpg.
Thanks in advance, Jim
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Old 12-01-2009, 01:09 PM   #2
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Re: 2001 8.1L issues

I know some people that use the 8.1 in their farm trucks some have well over 200k. that equals to about 600k in regular miles. one in particular I know of is beat mercilessly and stand up well. Far a gas mileage don't hold your brath. 6-8 is more real world. Even the 6.0's normally get itno the 11 mpg range. Jim
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Old 12-01-2009, 01:25 PM   #3
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Re: 2001 8.1L issues

My brother has a suburban with the 8.1 and it has 190K and still goes great. I would love to have that set up in my 67.
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Old 12-01-2009, 02:03 PM   #4
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Re: 2001 8.1L issues

That's good to know. I'm not too worried about gas mileage, I've got a p.o.s. s10 for that. Thanks a lot.
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Old 12-01-2009, 06:55 PM   #5
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Re: 2001 8.1L issues

8.1L’s are the absolute best big block GM ever made…..PERIOD. I personally own 3, two in trucks and another hanging on a stand for the next project.

The certified 340 HP and 455 lb ft of torque are very conservative ratings on this engine. With some minor ECM tuning the engine is good for 400 to 425 HP without changing a single hard part. The number 1 improvement to the calibrations is to have a tuner turn off Torque Management. That alone will add around 60 HP.

I work for a manufacturer that builds stripped chassis to the RV and commercial industry. We have sold more 8.1L engines since 2000 than GM did in the Silverado/Sierra platform. The warranty exposure for 8.1L hard part failures is virtually nonexistent.

About the only problem with the 8.1L the crank position sensor is notorious for failing on 2001 and 2002 model year engines. GM created a new designed sensor starting with the 2003 model year. All service parts are of the later design. You can identify the new design vs. the old by the single O-ring, but you have to remove the sensor to see the O-ring(s). If this truck hasn’t already received a new sensor already in it’s like that would be the very first thing I would replace when you get it home. My 2001 Silverado got a new sensor at 47K miles when it broke down and had to be towed to a dealer while I was traveling on business, which was covered by the 5 year/50,000 mile emissions warranty. If you change the sensor yourself, be very careful as it can break off inside the engine block easily and it is in an ugly spot between the firewall and back of engine (about the same spot at the oil pressure sensors on the older big blocks). Soak it very well with penetrating oil before trying to pull out.

2005 was a bad year for oil pump shafts but when the shafts break, the engines are not damaged as the ECM turns off the fuel once oil pressure disappears. Other than that….they are awesome engines that nobody seems to notice as the Dirtymax stole the spotlight.

As far as fuel economy, my 2001 with a manual trans gets 10 MPG loaded, unloaded, idling, towing, being towed or just sitting in the garage with the engine off. My point is…you can count on 10 MPG, which my 6.0L Silverado doesn’t get much better. Throw a trailer behind the 6.0L and the MPG drops to 7 or 8, while the 8.1L doesn’t care and still gets 10 MPG. Hell, people with 20,000 lb motor homes are pulling down 8 - 10 MPG with this engine.

You can also count on dumping a quart of oil into the 8.1L like clockwork about every 1,200 miles or so. That is just the nature of a big bore gas engine…they like oil. That all said, I wouldn’t worry much about the 8.1L, I would worry about the rest of the truck falling apart around the engine. GM trucks as of the past 10 years haven’t impressed me much in the durability department.

While we are on this topic, we should have a moment of silence GM Powertrain stopped production of the beloved big block in Tonawanda, NY just a few weeks ago.
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Old 12-01-2009, 07:14 PM   #6
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Re: 2001 8.1L issues

Here is a summary from GM Powertrain on the 8.1L. Gives me wood every time I read this.


Vortec 8100 (L18) Truck Engine Summary

• Application in Chevrolet Kodiak, GMC TopKick (medium-duty trucks) and Workhorse Custom Chassis
• Chevrolet Express and GMC Savana
• Powertrain Control Module and Software with Additional Monitoring Functions
• Improved Denso O2 Sensors
• Solid-State Oil Pressure Sensor
• Revised Electronic Throttle Body
• Coolant Path to Heater Core Revised on Chevrolet Silverado and GMC Sierra
• Revised Catalytic Converters
• Revised Oil Fill Tube and Cap
• Revised Oil Level Indicator
• Sight Shield Revised for Chevrolet Silverado, Suburban and Avalanche and GMC Sierra and Yukon XL
• Starter for Chevrolet Silverado, Suburban, Avalanche and GMC Sierra and Yukon XL
• Exhaust Valves Revised on Marine Variant


FULL DESCRIPTIONS OF NEW OR CHANGED FEATURES

APPLICATION IN CHEVROLET KODIAK AND GMC TOPKICK
The Vortec 8100 8.1L V8 (L18) is now offered in the Kodiak and TopKick, or commercial duty Family II and Family III trucks. These chassis-cabs provide the foundation for a host of vehicles from delivery vans to small dump trucks. The Vortec 8100 will be available with three gross vehicle weight ratings (GVWR): 16,000, 18,000 and 19,500 lbs. The Kodiak and TopKick replace 3500 HD and medium-duty chassis cabs. The 8.1L was launched in Kodiaks and TopKicks built from early calendar 2002 as 2003 models.

Depending on how the vehicle is ultimately finished, Family II and Family III trucks can generate far greater electrical demands than the typical truck. For these applications, the 8.1L can be equipped with two 105-amp alternators rather than a single 140-amp alternator (the second alternator is mounted on the right side of the engine). The accessory drive belt is therefore longer in these applications.

POWERTRAIN CONTROL MODULE AND SOFTWARE WITH ADDITIONAL MONITORING FUNCTIONS
A new Powertrain Control Module (PCM), called P59, manages the 8.1L. With this new PCM, processor clock speed increases from 21 to 24 mHz and memory capacity doubles to 1.1 megabytes. The PCM also manages the 4.3L V6 (LU3) and all gasoline-powered Vortec V8 truck engines, and provides one of the most sophisticated engine control systems in the industry.

Commonality offers the advantage of reducing inventory complexity and increasing efficiency at various assembly plants. More important, P59 offers the most precise engine management possible, optimizing performance according to temperature or operating conditions and virtually eliminating unintended variation in every function it controls, from ignition timing to fuel delivery to transmission shift points. It also allows GM Powertrain engineers to monitor more engine operations and improves the accuracy and robustness of the OBDII (On-Board Diagnostics) system.

For example, the PCM now measures electrical current flowing to the oxygen or 02 sensors (crucial components of the emissions-control system) on vehicles equipped with the Vortec 8100. Previously, the O2 sensors were monitored with a time-to-activity algorithm, which required more measurement latitude to ensure proper operation. The new PCM more quickly reports a malfunction in an O2 sensor with virtually no margin for misreporting. It also allows a new Engine Off Natural Vacuum (EONV) diagnostic for the Onboard Refueling Vapor Recovery system (ORVR), which reduces evaporative emissions by preventing gasoline vapor from escaping the vehicle into the atmosphere. With EONV, the PCM continues to operate when the engine is turned off, monitoring pressure in the fuel tank and ORVR system. If pressure bleeds off more quickly than ambient temperature and other conditions indicate, the PCM can determine whether the system has a leak, even when the vehicle is parked. The new PCM ensures that the engine operates according government emissions regulations. And thanks to its precision, it will also reduce the number of false alarms— OBDII “service engine” warning lights—that require dealer intervention.

The new PCM is roughly the same size as the PCM it replaces and is installed in the same place as the previous PCM in various applications—in all applications on the firewall or inner fender, depending on the vehicle. There is no visible difference in the engine bay.

IMPROVED DENSO OXYGEN (O2) SENSORS
The Vortec 8100 has new oxygen (O2) sensors. These O2 sensors have the same 6.6-volt heat rating as the parts they replace, allowing them to achieve closed loop operation—and maximum exhaust emissions reduction--in minimum time. The new sensors allowed engineers to implement the current monitoring function provided by the new PCM, and they are common to other truck gasoline V8s.

SOLID STATE OIL-PRESSURE SENSOR
The 8.1L now has a fully electronic, solid-state oil pressure sensor, replacing an analog/mechanical sensor. The solid-state sensor is installed in the same location in the engine block, but it has no mechanical parts, increasing reliability. Its introduction coincides with a new electronic instrument package in some applications.

REVISED ELECTRONIC THROTTLE BODY
The Electronic Throttle Control (ETC) system on the 8.1L uses a new throttle body and Throttle Actuator Control (TAC) module. The throttle body’s diameter (75 millimeter) has not changed, but the new part features a ``wrap around’’ throttle motor. The electric motor that operates the throttle plate is literally built around the throttle body and responds more quickly to commands from the TAC. The new throttle body is now common to all gasoline-powered GM truck V8s.

Before the Vortec 8100, ETC was largely reserved for premium passenger car engines and some heavy duty trucks. There is no mechanical link between the accelerator pedal and the throttle. Besides throttle pedal angle, the PCM measures other data, including the transmission's shift points, in determining how far to open the throttle. ETC delivers outstanding throttle response and can be calibrated to match demands in different applications.

COOLANT FLOW FROM HEATER CORE REVISED ON SILVERADO AND SIERRA
In the 8.1L applications, the flow pattern for engine coolant has been revised to heat the cab more quickly during cold temperature operation.

The heater core is a small radiator inside the vehicle’s instrument panel, behind the engine firewall. Hot coolant from the engine flows through the heater core, where the ventilation fan forces heat through ductwork to the dash vents and into the cab. In extremely cold temperatures, large displacement engines such as the 8.1L can take some time to reach a temperature sufficient to heat the cab. GM engineers have developed a simple, effective method to increase customer comfort by shortening the time it takes to heat the cab.

On Silverados and Sierras, the heater return hose is now routed into the radiator return hose rather than the radiator itself. That means the coolant flowing in and out of the heater core bypasses the radiator, where coolant is at its coldest temperature anywhere in the cooling system. Coolant flowing to the heater core stays out of the radiator until the engine reaches full operating temperature and the thermostat opens. This allows the cab to heat more quickly, meeting GM’s stringent time standard, without reducing cooling capacity during high-temperature operation.


CATALYTIC CONVERTER REVISED
The mix of precious metals in the 8.1L catalytic converter has been revised for all applications to meet more stringent 2003 exhaust emissions standards. The new converter has the same volume as the one it replaces, with similar architecture. The difference lies in the combination of platinum, palladium, rhodium and other rare metals in the converter substrate, or core. These metals create the chemical reaction that turns the majority of exhaust emissions into oxygen and water vapor. The combination has been optimized to achieve emission standards with more of the common varieties of these metals and less of the rarest types. This process limits environmental impact and keeps cost to the customer as low as possible.

REVISED OIL FILL TUBE AND CAP
The oil fill tube on 8.1Ls built for Silverado and Sierra has been revised to accommodate the new throttle body. The tube is angled more sharply as it rises from the engine block. It is also manufactured from molded plastic rather than steel, and sealed with an O-ring rather then a press-fit seal (the fill tube on L18s built for Workhorse Custom Chassis is still made of steel). Finally, the fill tube on all 8.1Ls except those built for the Chevrolet Kodiak and GMC TopKick, have a new corporate cap with a global symbol rather than the word ``oil.’’

REVISED OIL LEVEL INDICATOR
The word “Oil” stamped on the dipstick has been removed to comply with global labeling laws.

SIGHT SHIELD REVISED FOR CHEVROLET SILVERADO, SUBURABAN AND AVALANCHE AND GMC SIERRA AND YUKON XL
The thermoplastic sight shield or ``Vortec 8100 cover’’ around the 8.1L intake manifold and fuel rail has been revised to fit over the new throttle body. The sight shield dampens mechanical noise from the engine and gives the Vortec 8100 its up-to-date, finished look.

STARTER FOR SILVERADO, SUBURABAN, AVALANCHE, SIERRA AND YUKON XL
8.1Ls built for these applications are equipped with a different starter than other applications. Specifications are virtually identical, but this starter motor requires no heat shield and offers mass and packaging advantages. These applications now require a smaller heat shield for the knock sensor.

EXHAUST VALVES REVISED ON MARINE VARIANT
Exhaust valves on 8.1Ls built for marine applications are no longer treated with a Stellite surface hardener. There is no functional change for the customer. The Stellite-faced valves for marine use date to the leaded-fuel variant of the engine. Production of leaded-fuel 8.1Ls ended after the 2001 model year. All export engines are now built to U.S federal emission standards, which ensures that all Vortec 8100s produce the fewest exhaust emissions possible and allows GM Powertrain to focus further development on a common engine.

OVERVIEW
Introduced in the 2001 Chevrolet Silverado and Suburban and GMC Sierra and Yukon XL, the 8.1L is the legendary GM Big Block for a new millennium, with a longer expected useful life and horsepower and torque that surpass the competition. GM's leadership in big-block V8 technology dates to 1958, when the Vortec 8100's progenitor was launched with 348 cubic inches of displacement, in the full-size 1958 Chevrolets. The 348 was followed by several variants, including a 409, 366 and 427. In 1970, the 454-cubic-inch big-block was introduced. It was retooled in 1991 as the Vortec 7400--a truly powerful pickup engine that met stringent 1990s emission requirements. The Vortec 8100 bears little resemblance to those engines, beyond its bore centers and bore diameters, but it maintains a tradition of outstanding durability and class-leading power. Based on published figures in January 2002, the engine delivers more horsepower and torque than any gasoline engine in the heavy-duty pickup market.

After extensive analysis of competitors' engines, the 8.1L development team set a goal of 200,000 miles of useful life without major repairs--and then achieved it. The engine has been tested and validated to meet this 200,000-mile durability standard. Before it was ready for production, the 8.1L had to pass the ``Marine Dock'' test, in which it is run at full throttle for 300 consecutive hours, and a minimum of 1000 hours at full-throttle operation for truck applications. .

Durability is only one component of success in the heavy-duty pickup market. Another is outstanding power, and measured by both horsepower and torque, the Vortec 8100 beats its V10 competition.
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Old 12-08-2009, 02:05 PM   #7
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Re: 2001 8.1L issues

Thanks for all the info. I bought the truck and will post some pics when I pick it up on saturday.
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Old 12-09-2009, 04:20 PM   #8
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Re: 2001 8.1L issues

is the 8.1 a 454 if so why is a 7.4 a 454 or is the 8.1 a 502
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Old 12-09-2009, 04:34 PM   #9
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Re: 2001 8.1L issues

Quote:
Originally Posted by munger View Post
is the 8.1 a 454 if so why is a 7.4 a 454 or is the 8.1 a 502
7.4L is 454c.i, 8.1L is 496c.i., 502c.i. is a 8.2L
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Old 12-09-2009, 11:43 PM   #10
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Re: 2001 8.1L issues

ok thanks
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Old 12-10-2009, 12:07 AM   #11
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Re: 2001 8.1L issues

One way to figure out cubic inches from liters is to multiply the liters by 61.3. Or divide when converting C.I.D. to liters.

7.4L x 61.3 = 453.62 C.I.D

8.1L x 61.3 = 496.53 C.I.D

502 cid / 61.3 = 8.189 Liters
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Old 12-11-2009, 07:09 PM   #12
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Re: 2001 8.1L issues

Quote:
8.1L x 61.3 = 496.53 C.I.D

502 cid / 61.3 = 8.189 Liters
this cant be right..

if you do multiply by 61.3... how come 8.1L x 61.3 = 496..
and 502 / 61.3 = 8.1?
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Old 12-11-2009, 11:49 PM   #13
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Re: 2001 8.1L issues

Quote:
Originally Posted by 69halfton View Post
this cant be right..

if you do multiply by 61.3... how come 8.1L x 61.3 = 496..
and 502 / 61.3 = 8.1?
Dude, you got to take off your other shoe and count those toes too.

Actually, if you want to be nit-picky about it….

8.1 x 61.3 = 496.53
(rounds up to a 497 CID)

502 / 61.3 = 8.1892333789559543230016313213703
(rounds up to a 8.2L)

I doubt 61.3 is actually the natsazz conversion but it is pretty darn close. There really isn’t a big CID displacement change when you get down to tenths of liters. That said, 61.3 still gets you pretty dang close to what they are. Unless you want to go out and measure the bore and stroke of all these engines with ISO certified measuring devises and post up your results.

Keep in mind no two engines will be manufactured exactly the same with the exact same bore and stroke and there will be upper and lower spec limits spread over large quantities of engines manufactured that will need to be factored into your equation. Plus you will need to recertify your ISO certified measuring devise after 100 engines. So, when you’re all done averaging your ISO certified tool results and averaging all the bore and stroke samples of engines like the manufactures do you would probably come up with 496 CID for the 8.1L and 502 for the 8.2L.

61.3 sounds like an easy conversion now don’t it?

Last edited by DirtyLarry; 12-12-2009 at 03:40 AM. Reason: word order
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Old 09-27-2010, 12:05 AM   #14
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Re: 2001 8.1L issues

I know this is an old thread, but I came across looking for info for an 8.1 conversion i would like to do. Noce work DirtyLarry

and BTW

the most correct conversion for CID to Liters is

CI X 61.023=Liters
(from my auto book)
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Old 03-20-2011, 01:13 PM   #15
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Re: 2001 8.1L issues

Quote:
Originally Posted by 63chevyll View Post
CI X 61.023=Liters
(from my auto book)
That's backwards. It should read:

CI=Liters*61.023
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Old 07-08-2014, 11:25 AM   #16
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Re: 2001 8.1L issues

DirtyLarry, I know i'm again looking up at an old thread, but do you just use local tune shops for your PCM or do you run a handheld programmer or EFI LIVE?

Thanks,

Jack
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Old 08-10-2015, 05:48 PM   #17
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Re: 2001 8.1L issues

Quote:
Originally Posted by DirtyLarry View Post
8.1L’s are the absolute best big block GM ever made…..PERIOD. I personally own 3, two in trucks and another hanging on a stand for the next project.

The certified 340 HP and 455 lb ft of torque are very conservative ratings on this engine. With some minor ECM tuning the engine is good for 400 to 425 HP without changing a single hard part. The number 1 improvement to the calibrations is to have a tuner turn off Torque Management. That alone will add around 60 HP.

I work for a manufacturer that builds stripped chassis to the RV and commercial industry. We have sold more 8.1L engines since 2000 than GM did in the Silverado/Sierra platform. The warranty exposure for 8.1L hard part failures is virtually nonexistent.

About the only problem with the 8.1L the crank position sensor is notorious for failing on 2001 and 2002 model year engines. GM created a new designed sensor starting with the 2003 model year. All service parts are of the later design. You can identify the new design vs. the old by the single O-ring, but you have to remove the sensor to see the O-ring(s). If this truck hasn’t already received a new sensor already in it’s like that would be the very first thing I would replace when you get it home. My 2001 Silverado got a new sensor at 47K miles when it broke down and had to be towed to a dealer while I was traveling on business, which was covered by the 5 year/50,000 mile emissions warranty. If you change the sensor yourself, be very careful as it can break off inside the engine block easily and it is in an ugly spot between the firewall and back of engine (about the same spot at the oil pressure sensors on the older big blocks). Soak it very well with penetrating oil before trying to pull out.

2005 was a bad year for oil pump shafts but when the shafts break, the engines are not damaged as the ECM turns off the fuel once oil pressure disappears. Other than that….they are awesome engines that nobody seems to notice as the Dirtymax stole the spotlight.

As far as fuel economy, my 2001 with a manual trans gets 10 MPG loaded, unloaded, idling, towing, being towed or just sitting in the garage with the engine off. My point is…you can count on 10 MPG, which my 6.0L Silverado doesn’t get much better. Throw a trailer behind the 6.0L and the MPG drops to 7 or 8, while the 8.1L doesn’t care and still gets 10 MPG. Hell, people with 20,000 lb motor homes are pulling down 8 - 10 MPG with this engine.

You can also count on dumping a quart of oil into the 8.1L like clockwork about every 1,200 miles or so. That is just the nature of a big bore gas engine…they like oil. That all said, I wouldn’t worry much about the 8.1L, I would worry about the rest of the truck falling apart around the engine. GM trucks as of the past 10 years haven’t impressed me much in the durability department.

While we are on this topic, we should have a moment of silence GM Powertrain stopped production of the beloved big block in Tonawanda, NY just a few weeks ago.
hi D L

do you have a tuner you could recomend for my 2002 GMC 2500HD 4x4 8.1 vortec allison...
thank you for the great info about a great engine...
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Old 04-25-2017, 10:18 PM   #18
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Re: 2001 8.1L issues

Newbie to the board.

Have to say...Dirty Larry provided the motivation.

1972 K2500 4x4. With Dirty Larry power.

Some day..I'll figure out how to post pics
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