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

Dyno-Flogging GM’s Budget 350 Crate Engine

Jeff Smith Sep 1, 1999

Step By Step

The Goodwrench 350 engine comes as a long-block assembly complete with an oil pan, timing chain cover, and valve covers. This Goodwrench motor came from Scoggin-Dickey, delivered directly to our doorstep. Complete with a three-year/50,000-mile warranty, the price was right at $1,190 plus shipping.

This is a collection of the small parts we needed to complete the Goodwrench and get it running. A water pump, a fuel pump, a Fel-Pro intake gasket, a fuel pump mounting plate, a distributor hold-down, an ARP balancer bolt and fuel pump pushrod, and a timing indicator all came out of the PAW catalog. The oil filter adapter, dipstick, and tube all came from our local Chevy dealer. This particular HEI is a bone-stock distributor from GM Performance Parts. The only other miscellaneous parts you’ll need will be oil, a filter, spark plugs, plug wires, and fuel.

Whenever you start a new engine for the first time, it’s best to pressure-lube it. We used a 1/2-inch drill motor, a homemade pre-luber, and an oil pressure gauge. With the oil and filter in place, spin the oil pump clockwise until you read oil pressure on the gauge. It’s also a good idea to bump the engine over a couple of times while doing this to ensure everything is well-lubed.

In addition to the cast-iron 2-inch exhaust manifolds, our test included the right side heat riser valve as well. This is necessary to connect the stock exhaust pipes, but you could drill out the valve itself to improve flow. We chose to leave it in place for our test.

The Hooker headers are standard chassis headers for early Novas but represent a typical street header with 1-5/8-inch primary pipes and a 3-inch collector. We also intend to test the intermediate-length headers for this engine.

The baseline induction system consisted of a factory aluminum intake and a dependable Q-jet. The intake is an LG-4 305 style that has a decent reputation, but the only place it did well was under 2,700 rpm. This time-honored Q-jet has proven itself over many years of trouble-free operation. What many Chevy enthusiasts don’t know is that the Q-jet is rated at 750 cfm. At the 260hp level, however, the engine is barely using more than about 500 cfm.

All dyno work was performed at Ken Duttweiler Performance in Saticoy, California. All tests were performed using 92-octane pump gas, but at 8.1:1, we probably would have seen similar (if not better) results with 87-octane fuel.

Ignition duties were handled by an out-of-the-box Chevy HEI distributor along with a set of MSD wires and Bosch spark plugs.

We used a Fel-Pro 1256 intake manifold gasket to seal each intake to the engine. The silicon rings around the intake and water passage ports seal the ports to prevent vacuum leaks.

The Edelbrock Performer intake made a world of difference in our Goodwrench 350. Combined with the Hooker headers, we saw an excellent 265 hp at only 4,300 rpm and 350 lb-ft of torque at 3,600. The combination of the intake and headers was worth as much as 59 lb-ft of torque at 3,400 rpm!

Cast-iron exhaust manifolds are incredibly restrictive, even on a stock engine like the Goodwrench 350. The iron manifolds are connected with a set of 21/4-inch dual pipes bolted to a set of Hooker mufflers.

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.


Scoggin-Dickey Parts Center
Lubbock, TX 79424
Hooker Headers
Aberdeen, MS 39730
Performance Automotive Warehouse
Chatsworth, CA

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