6.5L Turbo Diesel Blazer Project

[More Power]

Here is a photo from the archive showing what the Blazer looked like in the year 2000 when I owned it the first time, and then again (below) in 2010 when, like the prodigal son, it found its way home...



The Blazer's original engine/parts were out of view in the bed of my truck here. We used a combination of tow straps and a come-along to get the Blazer onto the trailer. Sorta reminded me of my teen years when most of my vehicles came home the first time in much the same way (towed home without an engine)... It's amazing that way back then my parents and neighbors responded with some degree of tolerance... and patience... Luckily, the HOA Karen hadn't been invented yet...

Engine numbers:



This Blazer's original (and current) engine incorporated a "599" block (last 3 digits of the block casting number). The above photo is a shot of the engine valley, which is one place where the number "599" appears. The next photo shows where the number "599" also appears.



The complete block casting number "10149599" can be found on the upper left side of the bell-housing flange. The "599" is, in my opinion, the best GM block casting produced for the 6.5. These blocks were also used in the naturally aspirated and mechanically injected (DB2 fuel injection pump) 1991-1993 6.2L diesel equipped vehicles (mostly Canadian pickup truck market and utility vehicles here in the U.S., such as Postal vans). The only known difference between the 6.2L and 6.5L "599" blocks was bore diameter. So, a "599" 6.2 can be bored to a 6.5 without fear of thinning the cylinder walls too much.

Some years ago, there was a company in Georgia that acquired about 1,500 retired 6.2L diesel-equipped U.S. Postal vans. They all had a naturally-aspirated "599" 6.2L diesel installed. As far as I know, all of these "599" engines were bored to 6.5L specs by that Georgia company, and then sold to eager buyers. Our Dr. Lee acquired one of those engines for his 1984 Chevy C10. Dr. Lee has since sold his truck, but you can still see the article that explains how his was built, including how the engine was assembled. See: https://www.thedieselpage.com/article/leestruck.htm

Another distinguishing feature of the 599 was the introduction of a one-piece rear main seal. All earlier engines used a 2-piece rear main seal. Curiously, all of the 1994 6.5 vehicles I've checked all had a "599" block. Even the spare/used 1994 6.5L engine I bought in 2021 is also a "599". The casting foundry apparently produced a lot of them.

It's considered a bonus to acquire a 6.2L "599" because of the added flexibility offered during a rebuild... You can either keep it a 6.2 or bore it to a standard bore diameter 6.5. Most go the 6.5 route, especially if you're installing a turbocharger because the 6.5 piston crowns are all anodized, making them a bit more tolerant of high combustion temperatures.

I've used modeling clay a time or two in the past when I needed to "see" the casting number or date code of a 6.5 engine that was still sitting in the vehicle. You can't see the casting numbers by looking over the rear of the engine, but you can feel them (from beneath the vehicle), which allows you to make an impression of the casting numbers using modeling clay.




This is the block's 4-digit casting date code "M033" for the Blazer's original engine, which was rebuilt for this project. The "M033" date code indicates a December (M) 03, 1993 casting (the letter I is not used in the alphabet list due to a possible confusion with a number 1, A=January, B=February, C=March, etc. all the way to M=December).



These casting numbers appear on the block surface just forward of the passenger side block deck. Being cast in 1993, and as a "599", this block could have been used in the 6.2L diesel equipped vehicles produced in the 1991-1993 model years and then in the 6.5L turbo diesel's introductory model year of 1992 through possibly as late as the early 1995 model year depending on how many 599 blocks had been cast/used.

Because this block casting could be used in either a 6.2L engine or a 6.5L engine, GM chose to leave the displacement numbers out of the alpha-numeric identification as shown here in the above image. This meant there would be a space between the two sets of letters i.e. "GM LD". Turns out, this gap between letter pairs is another identifier of the "599". In earlier 6.2L and later 6.5L castings, there would either be a "6.2" or "6.5" in that gap, i.e. "GM 6.2 LD" or "GM 6.5 LD". The "LD" refers to "Liter Diesel", not "Light Duty"/"Heavy Duty".

The yellow arrow on the right points to a "005" stamping on the machined deck surface, indicating that the block deck had been machined .005". I installed +.010" Fel-Pro head gaskets during the rebuild to help ensure piston protrusion wouldn't be a problem.

There will be a pop quiz later...