Redefining Classic: The 300HP Cummins Heartbeat of a ’72 K5 Blazer

An Excellent Cummins Swap in a Vintage Classic

We’ve all heard the expression that something is so clean you could “eat off it,” but it’s hardly ever true. Even in show trucks, there’s usually parts that are dusty, or oily, or have secret rusted bolts. We can confidently say that this is not the case for Jim Martin’s ‘72 K5 Blazer from Northern California. The paint is gorgeous, the engine bay is pristine, and even the underside is absolutely immaculate. It’s probably one of the cleanest Cummins swaps we’ve ever seen, and that’s saying something.

Now Blazers are classics, but they’re also known to not have a ton of power, and to get horrible fuel economy with the factory gas engine. Guess what solves all that, a diesel! Jim’s Blazer has been swapped with a classic 12-valve Cummins out of a ‘91 Dodge. The factory 160-hp engine is kind of a snoozer, so Jim’s Cummins has been upgraded with a turned-up fuel screw, governor spring kit, upgraded compressor wheel, and now makes approximately 300hp along with 800 lb-ft of torque. Reliability issues like the killer dowel pin have also been addressed. Power is routed out through a custom muffled dual 3-inch exhaust system.

Jim likes to shift his own gears, so he chose an ultra-strong NV4500 out of a ‘94-’98 12-valve Dodge as a suitable manual box. The five-speed transmission was adapted to the First-Generation engine with a starter, engine plate, and flywheel out of a Second-Generation donor truck. This manual was then further adapted to an NP205 transfer case out of a First-Generation truck. As you can see the driveline is a mishmash of First and Second-Gen parts, but it works.

With the diesel engine and trans swapped in, there was still the issue of getting the truck to go down the road. Jim accomplished this with such niceties as a Readhead steering box with a crossover link, while the clutch and hydroboost braking system were adapted from a ‘94 Dodge donor truck. Axles that were study enough to handle the diesel power were swapped in too, with a GM 14 bolt in the rear, along with a Dana 60 out of a 1-ton truck up front.

Now we get on to what Jim calls “the glitter stuff,” which makes the truck look the way it does. There’s 17-inch polished wheels by US Indy Wheels, and Ididit steering column, Car Tunes custom stereo, and Taylor Wings cargo box. A lot of it is functional too: like the Autometer gauges, and the Speed Hut Speed Box electric-to-mechanical conversion for the speedometer. The interior itself also has a 6-point rollcage built by David Virga and custom bikini top by West Coast Custom Interiors. Jim sits in comfy Corbeau seats, and there’s LED lightning throughout. You might also think the paint is custom but it’s actually a factory Medium Blue PPG hue.

You have to stand there for a minute to take Jim’s Blazer all in. It’s not just one thing that attracts your attention but everything that is so well-done. He’s modified virtually every part of the vehicle, but the fact that he’s retained a factory-style look is perhaps the best of all. Jim would also like to credit Ken Imler from Imler Diesel and the original owner Andy Byrne for their help. We’d like to credit Jim for building such an awesome ride, one that’s definitely worth featuring in the pages of Diesel World.