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6.2L Buildup

Turning an old 20-Something GM Diesel Into a Modern Power Puller

Photography by Bruce Smith

They are plentiful, they are durable, and they are cheap. In addition, they're simple and economical. Those five factors are what make the venerable 6.2L Chevrolet diesel a very popular builder these days, especially if you are planning on plopping one under the hood of an older 1/2-ton pickup or SUV in place of a gas V-8. The engines were a mainstay in the '82-'93 GM light-duty truck line under the hoods of Chevrolet and GMC pickups, Suburbans, and fullsize vans. The 6.2L was replaced in 1994 by the 6.5L, which was subsequently replaced by the Duramax 6600 in 2001.

Finding a Good Donor
Even though they have been out of production for nearly a decade, there are still a lot of 6.2Ls on the road-and countless others sitting idle that could easily be put back on the road. What that means to the diesel-loving do-it-yourselfer is if you are in need of a good diesel engine for your older pickup or SUV, you can find the 6.2Ls with little effort. They are lying around everywhere you look. Literally. If you spot an old, beat-up GM pickup or big van sitting beside a barn, wedged in the farthest row of junkyard dogs, or serving as a trellis for a growth of blackberries, it probably has a 6.2L diesel under the hood. These parts trucks are fine for just that-parts. But, the ones you probably want to check out for rebuilding the diesel are not those rusting away, but rather those listed in the used vehicles section of any newspaper. You know the ones-those old GM diesel pickups that still run and can be had for less than the price of a set of new tires, or better yet, are being given away.

Many of these bargains are parked either because the truck around the engine has fallen apart or the engine itself, as the owner sees it, was nearing the end of its life and the owner simply moved on to other modes of transportation rather than deal with the cost of rebuilding either the truck, the diesel, or both. Believe it or not, most of the time, these trucks are being parted with because they will not start in cold weather because of a problem with the glow plugs or bad relays. If the truck isn't rusted completely into the ground and the engine hasn't been sitting under water, one person's junker becomes a diesel builder's treasure.

Builder/Buyer Beware
The caveat to this entire 6.2L rebuilding process rests on one thing: the year of the engine you use as your base. Heed this advice: If the engine you are contemplating as the builder is pre-'88, find a newer engine for the best performance and reliability from the rebuild at the cheapest price. As Warren Spears, the owner and co-builder of this project says, "If you raise the hood of the donor vehicle and you don't see a serpentine belt system, rapidly close the hood, thank the person for showing you the vehicle, and quickly walk away." We found that out the hard way on this rebuild. Our junkyard '82 C1500 diesel pickup cost $500. Warren sold the truck for parts, sans engine, for $400, so the C-model 6.2L ended up costing $100. However, as much of a bargain that was, it cost an additional $1,900 to upgrade the engine to the higher-performance, more reliable J-model by the time we bought reworked, later-model ('90-'92) heads for $900, the newer-model rocker arm assemblies for $200, and the brackets and drive accessories to convert the engine to the serpentine-belt drive for $800. That doesn't include the aggravation and time involved tracking down the better parts and figuring out how to upgrade the engine to the more reliable, later-style 6.2L. "We'd had been far better off spending $2,000 on a '93 model that had a good body and the latest version of the 6.2L," reminisces Spears. "But, hindsight, as they say, is always 20/20." Thankfully, Warren had several aces-in-the-hole. One was at the local Chevy dealer. Daryl "Woody" Woods, a superb parts counterman at DeRussy Chevrolet in Bay St. Louis, Mississippi, took the time and knew where to find all the parts to make the upgrade. The other great help in this rebuild was our local O'Reilly Auto Parts store in Long Beach, Mississippi, where Jason Carey, the store's manager, provided similar parts assistance, including providing a Federal Mogul Premium Master Engine rebuild kit-and a number of other must-have items that cropped up along the way.

Without those two guys, "The Diesel Page 6.2L Diesel Engine" reference manual, and a copy of Haynes Diesel Engine Repair Manual, undertaking a 6.2L rebuild for the first time would have been a lot more "interesting." The Diesel Page manual is a must-read before you undertake a 6.2L rebuild. Of course, if the engine you plan on giving new life to is an '82-'88, and it's still running, stay the course and rebuild it back to stock; the 25 extra ponies and 45 lb-ft of additional torque gained from the later-model, naturally-aspirated 6.2L might not be worth the time or cost needed to make the upgrade.

Rebuilding For Power
Rebuilding the 6.2L diesel is a comparatively cheap way to have reliable and capable diesel power. Instead of paying $6,500 for a crate 6.5L short-block, you can rebuild a 6.2L and kit it with a Banks turbo for about $4,500. As a note of interest, back in 1989, GM chose Banks as the 6.2L dealer-installed turbo option, and remained so until GM released its own 6.5L turbodiesel. This ultimate upgrade for the venerable 6.2L workhorses provides as much as 60-plus hp and 115-plus lb-ft of torque, plus 10 percent better fuel economy according to Banks.

Of course, we wanted everything we could get out of the ancient '82 we bought. That meant a lot of new parts and special attention to details to give it new life. In addition to the typical engine rebuild parts, we stepped up the power quotient on our builder by installing a Banks Sidewinder turbo kit-a dealer option GM offered in the latter days of the 6.2L. The $2,100 Banks kit includes everything from the Banks Ram-Air intake with cast air-filter housing to the Sidewinder turbo with turbocharger exhaust manifold, pressure-chamber-plenum boost tube, special radiator hose, and crankcase-vent duct. It also includes a complete 3-inch stainless exhaust system with a Dynaflow muffler.

Speaking of the power from a rebuilt 6.2L, we ran our "new" Banks' turbo'd engine on the dyno at Vanderley Racing Engines in Lyman, Mississippi, not far from where Karl Hagar and Warren Spears did the overhaul. Here's what we found: The original '82 6.2L delivered 130 hp and 240 lb-ft torque. Our "new" 6.2L delivered 58 hp more than the stock engine did and 110 lb-ft of torque between 1,100 and 1,800 rpm, and 40 hp and 85 lb-ft more power at 2,800. That puts our builder engine in the same power range as the 6.5 turbo found in today's GM heavy-duty pickups.

So, as you can see, the end result of a 6.2L GM rebuild is a stout, reliable, fuel-efficient diesel that runs as good as or better than the popular 6.5L turbodiesel. We expect to get a decade or more of service from this one-and a lot of raised eyebrows when we open the hood to show off how fine a 24-year-old turbodiesel looks. You should see similar results.

Our rejuvenated "High-Output" 6.2L is ready for the accessories and then off to the dyno. A little powdercoating for color gives the new engine just the right look to go with its performance gained from the rebuild and addition of the Banks Sidewinder turbo kit.

SOURCES
Karl Hager's Engine Service Diesel Service Group
Spears Auto Repair Federal Mogul/Sealed Power
O'Reilly Auto Parts
8-00/-755-6759
oreillyauto.com
The Diesel Page
Gale Banks Engineering
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216 comments
Layne Crea
Layne Crea

I had a 6.2 that I put over 200k miles on. About the only thing I had to do to it was replace glow plugs occasionally, and change the oil. It was reliable, and you could work on it yourself. It was also a dog.

Andrew Robertucci
Andrew Robertucci

Good luck keeping the head gaskets from blowing if you actually use it.

Josh Mecham
Josh Mecham

Save some time and money and do the right thing just drop a Cummins in it enough said!

Andrew Hershfeld
Andrew Hershfeld

Calvin only reason people say that the Powerstrokes are junk after the 7.3L is cause everyone thought they could work them to death with out doing maintenance to them. Using the wrong oils, fluids, after market filters, tunes....if ya did a few minor things and didn't use a tune these engines would last a long time.

James Slykhuis
James Slykhuis

I'd love an old 6.2 or 6.5 truck, good old Detroit diesels

Joel Case Sr.
Joel Case Sr.

Got 3 6.2s and one 6.5 its a constant job to keepm runnin all 3 cummins 7.2 cat and 7.3 idi IH just maintenance

Joel Case Sr.
Joel Case Sr.

Dmax Is assembled in moraine not manufactured parts r forged and founded in japan

Gaven Kemp
Gaven Kemp

The old 6.2 and 6.5 were seriously the worst diesel motors built. I've worked on several and not only are they a nightmare, the parts are getting more scarce as well. The thing I never understood about them is why didn't they have an I/C. Would've been beneficial.

Nitish Kurup
Nitish Kurup

Should've added another Turbo on the other side aswell, would've been a class apart.

Michael Raleigh
Michael Raleigh

No they don't. Lol go research something. Literally everything you just said is wrong. The duramax is built ENTIRELY in moraine ohio by DMAX corp. which is owned by GM. The only thing Isuzu ever did was CO-DESIGN the motor with GM. I swear you people are idiots.

John McDaniel
John McDaniel

I'd own one of these over any 6.0 powerstroke that's forsure gutless powerless lasts forever tows anything and can get mpgs just not fast from a to b but definitely gets there

Hunter Davis
Hunter Davis

I have a 1991 Chevy that's begging for yall to put that beautiful beast into

Griffin Krage
Griffin Krage

An old dog not much power but u couldn't kill it

Tyler Coulson Cooter
Tyler Coulson Cooter

Got a 93 6.5td 1ton. Making 325hp 510tq gets 23.8mpg hwy. 350000miles running like a clock

Seth Esparza-Vanpelt
Seth Esparza-Vanpelt

well isuzu was a big part of the development of the lb7 but builds them? no. they are not even the majority owner of the name today

Randy Bahl
Randy Bahl

Still take my old Idi 7.3 with the hypermax turbo set up

Travis Womack
Travis Womack

I got a 84 blazer with 1 ton axles on 44" tires 6.2 around 450k still runs fine.. have a 93 dodge 1 ton 4x4 cummins its broken.. at 253k had a 95 dodge cummind blew motor at 237k yea 6.2 reliable just not most power

Jeff Kramer
Jeff Kramer

I bet it makes more than 148 horse power now. My suburban has a 6.2 and thats all it makes

Nick Fischer
Nick Fischer

more stuff like this!!!!! maybe a gm 5.7 build just to see some sweet carnage .. just more odd ball builds

Eli Jack Douglas Stone
Eli Jack Douglas Stone

Smh. That article in the last mag about "That Guy" is so spot on. So many "That Guy" comments being made.

Zachary Stein
Zachary Stein

I've got a 6.5 2500 that is my daily driver, to be honest I love it, great power and sound, rides like a dream, and does what I need it to do without a fuss.

Jeff Ragland
Jeff Ragland

I had 4 new GMC's back in the 80's with the 6.2 i loved them 26 and more MPG on the HY and i was getting 22 around town

Jesse Stone
Jesse Stone

The 6.2 was a great motor not your modern day power house but most people on here prolly dont use their trucks like trucks anyway Cant go wrong with a Detroit Diesel!