6.5L DIESEL SPECS

G’day Jim,

I have an old 6.5 naturally aspirated mechanical engine, and I believe it to be underpowered. Is there a way of finding out how old the engine is and/or whether it’s a 160 hp version or a detuned version removed from a Post Office delivery van?

I’m having trouble getting specs from anywhere for testing. Where can I find out what year model my engine is and a source for a service manual? Please help.

Cheers, Tom Munns

Tom,

The non-turbo, light-duty 6.5L diesels were (mostly) rated at 160 hp. The 6.5L diesel engines used in delivery vans (Post Office) were rated slightly lower. However, power and torque are determined more by fuel injection system calibration than by vehicle application.

The best cure for an underpowered 6.5L diesel is a turbocharger. A GM or Holset turbocharger (such as that used for the 1994–1998 Dodge Cummins), along with a fuel calibration, will add 50 percent more horsepower and torque. That’s huge!

If this is a 1990s engine, you’ll find a four-digit block casting date code cast into the bellhousing flange behind the passenger-side cylinder head (right-side head). The code will begin with a letter—a=january, B=february, etc.—followed by three numbers. The center two numbers are the day of the month, and the last digit is the year in which the block was cast. For a 6.5L diesel cylinder block cast in the 1990s, a “6” as a fourth digit would indicate a 1996 casting date. A C106 code would translate to March 10, 1996. (The 6.5L diesel casting date codes transitioned to five digits in late 2001.)

As for a service manual source: Aside from genuine GM service manuals, available through www.helminc.com, you can also access an online subscription service through www.alldatadiy. com for the GM literature. For a less-expensive source for a physical book, have a look at www. thedieselpage.com/t&rguide.htm or www.haynes. com. Good luck.