Everyone's looking for a deal. It used to be that the only way to save money on an engine was to build it yourself. But today, crate engines are so plentiful and cost effective that unless you really want to build your own engine, it makes sense to buy a crate engine. We've spent some time researching the small-block Chevy market and it's tough to beat the 350 H.O. engine for the dollar-per-horsepower potential it represents.
We liked this engine so much that we decided to bolt one up to the dyno and flog on it for a few months to see just how much streetable power we could squeeze out of this little Mouse. The operant word here is "streetable." Over the next three months, we'll run several different combinations across this engine searching for solid overall power with decent idle quality. The goal here is an engine that can make 400 hp but still be docile enough for a daily driver. So with our navigation set, let's take a look at what goes into a basic GM Performance Parts 350 H.O. engine and how much power it makes.
350 H.O.Our plan was simple-find the highest quality small-block Chevy mail-order engine that has the best power potential for the least amount of money. After searching through the GM Performance Parts catalog, it quickly became clear that the 350 H.O. engine is an excellent deal. The engine is based on a block featuring a four-bolt main, one-piece rear main seal, cast pistons, forged powdered-metal 5.7-inch rods, and a nodular cast-iron crank. With 9.1:1 compression and a set of Vortec heads, this engine has a ton of potential. The long-block also comes with a flat-tappet hydraulic cam with stamped-steel guided 1.5:1 rockers. This is a decent cam, and combined with a dual-plane intake, 600-cfm carburetor, and headers, GM Performance Parts claims the engine will make an honest 330 hp.
Looking into this a little further, we also discovered a 350 H.O. short-block for about $800 less than the long-block. But after we added up all the parts we'd have to buy to assemble the engine, the long-block deal looks very attractive at Scoggin-Dickey's price of $2,300. You would need a one-piece rear-main-seal oil pan, timing cover, gaskets, a cam, lifters, pushrods, rockers, heads, and all the other gaskets plus a few other minor items. Frankly, the price of the 350 H.O. cam, lifters, pushrods, heads, and valve covers is the price difference, making the long block a pretty good deal.
The deluxe package stacks even more parts on the long-block with an aluminum dual-plane intake, 600-cfm Holley carb, HEI distributor, water pump, damper, dipstick, chrome valve covers, oil filter, and even spark plugs. This is a ready-to-run package where all you'd have to do is hook up the accessory drive and add oil and water. The deluxe package is significantly more money at $3,485, but you also don't have to run all over town searching for all the parts to piece this engine together.
The key to this package and why it represents such a power bargain isn't really the 330hp number as much as it is the potential it promises with the Vortec heads. From previous experience, we know that this engine is capable of 390-plus horsepower with a slightly bigger cam, intake, and carburetor. Yet the basic short-block and rotating assembly remains exactly the same. This is outstanding power for the money and for very little effort.
The TestFor testing, we bolted a complete GM Performance Parts 350 H.O. Deluxe engine up on Ken Duttweiler's dyno and let dyno whiz Ed Taylor run it through its paces. For a baseline, we decided to see how well this engine would do with cast-iron manifolds and a dual exhaust with generic 211/44-inch turbo mufflers. This is actually not the way GM baselined this engine (the company used 131/44-inch headers and the deluxe 600-cfm Holley carb for the 330hp rating). After some initial experimentation with ignition timing, we ended up with 37 degrees of total lead, and on 91-octane pump gas, the 350 pumped out 354 lb-ft of torque at 3,800 and an impressive 320 hp at 5,600 rpm. This is an 1,800-rpm powerband between peak torque and peak horsepower, and anytime you can crank out over 300 hp with iron exhaust manifolds, you're doing well.
The obvious next step was to toss on a set of headers, so Taylor bolted on Hedman 151/48-inch long-tube headers with no other changes. This delivered an amazing increase in both torque and horsepower, pumping the peak torque up to 383 lb-ft-a stout 29 lb-ft of torque increase at 4,000 rpm. The horsepower also jumped to 341 at 5,400, an increase of 21 hp over our stock exhaust baseline. But perhaps most importantly, the average torque increase with just the headers alone was a thumpin' 23 lb-ft of torque and 17 hp. If you do nothing else, headers are the best bang-for-the-buck-bolt-on for the 350 H.O.
We also decided to try a couple more things for this first episode of our street 350 H.O. Since the addition of the headers performed so well, we upgraded the exhaust system to a pair of Borla Pro X/S stainless steel mufflers and a true, mandrel-bent 211/42-inch exhaust system. Then, just for grins, we also bolted on a slightly larger Pro Vac 650-cfm vacuum-secondary carburetor from Quick Fuel Technology. The combination of the two elements created a slightly better power curve and added an average of 4 lb-ft and 4 hp across the board. This is not a huge increase, but it did push the 350 H.O. up to almost 390 lb-ft of torque at just under 350 hp.
ConclusionWith very simple bolt-ons, the 350 H.O. engine made some very impressive gains on the first dyno flog. When you consider this is a brand-new engine with 348 hp and a GM warranty, this is quite a bargain. Just to make this more enticing, we plugged the power numbers into the ProSim dragstrip simulator to estimate how well this engine would perform in a typical 3,500-pound street car with 3.54 gears, a TH350 trans, a 2,600-stall converter, and sticky tires. The program spit out an estimate of 12.98 at 104 mph. That's perhaps a bit quicker than we would expect, but low 13s at 102 mph is certainly achievable. Clearly, with a few more changes, it's possible to make more torque and horsepower without sacrificing this engine's very mild street manners. That's what we'll get to next month. As they say on TV, stay tuned.
Spec SheetEngine: 350ci small-block ChevyBore x stroke: 4.00x3.48HP & Torque: 330 hp @ 5,000, 380 lb-ft @ 3,800Compression: 9.1:1Block: Cast-iron four-bolt main, one-piece rear seal, PN 10105123Crank: Nodular cast iron, PN 14088527Connecting rods: Powdered metal forged steel, PN 10108688Pistons: Cast aluminum, dished, 51/464-inch rings, PN 12361371Camshaft: 212/222 degrees @ 0.050, 0.435/0.460-inch lift, PN 24502476Heads: Vortec iron, 1.94/1.50-inch valves, PN 12558060Rocker arms: Stamped steel, 1.5 rail type, PN 10089648Valve covers: Centerbolt, chrome, PN 12355350Intake: Dual-plane aluminum, PN 12366573*Carburetor: Holley 600 cfm, vacuum secondary, PN 12497147*Distributor: GM HEI, PN 1104067*Water Pump: Cast iron, PN 12529305*As part of the 350 H.O. Deluxe package
The Long and ShortFor the budget conscious, the long-block version of the 350 H.O. is an excellent way to get the most out of this package, especially if you already have an intake, carb, and the other accessory pieces. If you are replacing an older small-block, keep in mind that this is a one-piece rear-main-seal engine, so you'll need either a new one-piece flexplate or flywheel. The H.O. engine is fitted with a flat-tappet cam, but the block is configured for a factory hydraulic-roller cam. We'll convert this H.O. engine over to a roller cam later in the buildup series, so if you're thinking of this conversion, it's a great idea. Just hang with us and we'll show it to you.
The Results Are In Test 1: Baseline run of H.O. 350 w/ cast-iron manifolds, 2-inch turbo mufflers and 37 degrees total timing w/91-octane fuelTest 2: Added Hedman 15 1/4-inch headersTest 3: Added Borla 2 1/2-inch stainless steel Pro X/S mufflers and QuickFuel 650-cfm carb
Test 1 Test 2 Test 3 RPM TQ HP TQ HP TQ HP 2,200 327 137 338 142 339 142 2,400 328 150 343 156 340 155 2,600 334 165 354 175 350 173 2,800 341 182 362 193 365 195 3,000 343 196 363 207 372 212 3,200 350 213 371 226 375 228 3,400 351 227 377 244 380 246 3,600 353 242 380 260 385 264 3,800 354 256 380 275 387 280 4,000 352 268 383 291 388 296 4,200 350 280 382 305 386 309 4,400 348 292 377 316 382 320 4,600 346 303 374 328 378 331 4,800 340 311 364 332 370 338 5,000 331 315 355 338 361 344 5,200 322 319 342 339 351 348 5,400 311 319 331 341 338 348 5,600 301 320 319 340 327 348 AVG 337.8 249.7 360.8 267.1 365.2 270.9 Gains +23 +17.4 +27.4 +21.2Parts ListThe following are part numbers for the different GM Performance Parts short-block and long-block combinations mentioned in the story. All prices were researched through Scoggin-Dickey Performance Center.
Component Source PN Price Short-block, less cam & lifters GMPP 12556121 $1,500 H.O. short-block, less cam & lifters GMPP 12510737 1,136 L98 long-block, 350 H.O. GMPP 12486041 2,300 Deluxe 350 H.O. engine, complete GMPP 12496968 3,485