GM 350 Crate Engine Build - The Goodwrench Quest, Part 1

In the world of small-block Chevys, there are literally hundreds of engines to choose from. The choices range from cheapie backyard rebuilds to $10,000-plus race motors. Among all of these engines clamoring for your attention, there is one that may be the deal of the century. For years, Chevrolet has offered the Goodwrench 350 as a brand new service replacement engine. While you can purchase this engine from any GM dealer in the country, there are a few dealers like Scoggin-Dickey that are offering Mr. Goodwrench for the outstanding price of $1,190! This isn’t some slapped-together rebuild, it’s an all new 350 long-block assembled with new parts. And better still, it comes with a warranty.

If you’re looking for a basic small-block that will deliver years of trouble-free operation, you’ll be hard-pressed to find a better buy. But since this magazine is called Chevy High Performance, we thought it would be fun to see what kind of voodoo we could do to extract more grunt from our Goodwrench Mouse. The plan was simple: borrow a Goodwrench 350 engine from Scoggin-Dickey, bolt it on the dyno, and run the wee out of it.

This first of several episodes started with a test of the basic engine package with a factory Q-jet intake, cast-iron exhaust manifolds, HEI ignition, and a full dual-exhaust system. The next test added a set of Hooker headers and finished with the addition of an Edelbrock Performer intake. All the tests were run on 92-octane pump gas.

The Engine

The Goodwrench 350 is unquestionably bread-and-butter basic. While all production small-blocks have employed a one-piece rear-main seal design since 1986, the Goodwrench 350 is assembled in Mexico and retains the classic two-piece pre-’86 design. This makes it an excellent choice for a basic hot rod motor for all pre-’86 cars since you don’t have to purchase a new flexplate or flywheel.

Starting with a four-bolt main cap block, the 350 employs a standard cast crank and cast-aluminum flat-top pistons with ductile-iron 5/64-inch rings. Chevy claims the compression is a wheezy 8.1:1, but after the test was over, we measured everything and came up with a slightly better 8.4:1. The good news with this low compression is that the Goodwrench engine should even run on 87-octane gas. The downside is that this low compression certainly sacrifices power. The long-block comes complete with an oil pump and pan, as well as a timing-chain cover and valve covers. The cam is a simple flat-tappet hydraulic with specs that are bone-stock tame. The 76cc chamber cast-iron heads (casting number 83417368) are fitted with 1.94/1.50-inch intake and exhaust valves and stock stamped-steel rockers.

Beyond the mechanical aspects, there’s also the GM warranty. According to Scoggin-Dickey, GM offers a three-year, 50,000-mile warranty on the engine as long as it has not be internally altered; this means that the warranty would be void if a performance camshaft was added or if the compression was increased. However, a performance intake manifold and/or headers are acceptable modifications. There are other warranty details too numerous to mention here, which you should investigate if you are considering purchasing one of these engines.

With shipping costs ranging from $125 to $165, depending on how far the engine must travel, you could have a Goodwrench 350 at your doorstep for $1,355 or less. One other important point is that Scoggin-Dickey buyers outside the state of Texas do not have to pay sales tax, which can represent a savings in excess of $100.

Dyno Testing

Freelancer, engine builder, and CHP’s man-about-town, Ed Taylor, ram-rodded the Goodwrench Mouse project for us at Ken Duttweiler Performance in Saticoy, California. The first test was to cork the 350 with a stock aluminum intake manifold, a Q-jet carburetor, and cast-iron exhaust manifolds connected to a pair of Hooker 2-¼-inch turbo-style mufflers. As you can see from the Test 1 results, the engine performed much better than GM’s stock 190hp rating, making 239 hp at 4,300 with peak torque coming in at 3,700 rpm with 324 lb-ft. This is a rather narrow powerband between peak torque and peak horsepower, and it was obvious that both the intake and exhaust systems were extremely restrictive. Remember, this is a stone-stock 350 with kerosene-compatible compression and a camshaft that barely bumps the valves off their seats. On the plus side, the engine made more than 250 lb-ft of torque from 2,500 to 4,800.

It was obvious the engine needed to breathe, so we pitched the cast-iron exhaust manifolds and bolted on a set of Hooker 1-5/8-inch headers. We retained the 2-¼-inch exhaust pipes and Hooker turbo mufflers, all obtained from PAW. The engine responded immediately to the exhaust system upgrade with as much as 53 lb-ft more torque at 3,400 rpm! To put that in perspective, that’s like a mild shot of nitrous. As you might expect, horsepower also improved, with 17 more horsepower at 4,500 rpm. We were certainly on the right track, but now the engine needed help with the induction side.

The route to adding more horsepower was obvious—the Goodwrench motor needed a better intake manifold. So, we unbolted the factory aluminum piece and bolted on an Edelbrock Performer intake. The Performer is drilled for both the square-flange Holley-style bolt pattern and the spread-bore Q-jet pattern, which makes installation easy. Within a few minutes, Taylor fired the engine back up and ran it through the 2,500- to 5,300-rpm power test. Looking at the power curves, the Performer lost a little power below 3,000 rpm, but more than made up for it with improved power in the mid-range. This is probably not a problem with the manifold as much as it reflects a calibration difficulty with the Q-jet that could have been solved with a bit more tuning. But overall, the combination of the Goodwrench 350, a set of 1-5/8 headers, an Edelbrock Performer intake, and a painfully stock Q-jet was worth 350 lb-ft of torque and 265 hp. Not bad for a stock motor and bolt-on parts!

Where Do We Go From Here?

We’re done for this installment, but hang on because we’re not nearly done beating on this little Chevy. The Scoggin-Dickey Goodwrench 350 will return in the next story, when we will pocket-port the stock heads and then try a better camshaft. Down the road, we’ve also got a set of aluminum Corvette heads and a set of Vortec production iron heads we’re going to swap into place as well as other parts combinations, bigger cams, different carburetors, and even some variations on the header theme. The Vortec heads and other GM hi-po parts come from GM Performance Parts, which can also be obtained directly from Scoggin-Dickey. So stick with us—we plan on beating the snot out of this Goodwrench crate engine to find out just how much power we can squeeze out of a budget small-block.