[DirtyLarry]

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.