Oh, General Motors, you practically went out of your way to confuse people with your engine displacements. We've already talked about how theChevy 350 and Pontiac 350 are completely different engines, but there's also the Oldsmobile 350. Oh, and the Buick 350, which was actually a 349, but what's a cubic inch between friends? 

Right now, let's focus on the Oldsmobile 350 and Chevrolet's first-generation small-block 350. We'll start with the most essential distinction between Chevrolet and Oldsmobile V8s: Chevrolet never converted its 350 to run on diesel (though Chevy did use the Olds diesel in some pickups). Any discussion of Oldsmobile 350s eventually gets around to the diesel, but before digging in too deeply, know that the Olds diesel V8 isn't that bad. Well, depending on the year and owner maintenance, at least. 

Here's some quick Chevy V8 history. In 1955, the small-block 265 Chevy V8 debuted to a chorus of cheers as Chevrolet took back the sales crown from Ford. The "mighty mouse" motor grew many sizes, from 283 cubic inches to 327, 350, and beyond, reaching as high as 400. It stayed in production with various refinements until it was replaced by the LS engines in 1997. The 350 Chevy small-block had a 4-inch bore and 3.48-inch stroke, and it was eventually blessed with aluminum heads.

The Oldsmobile 350 began life as a 330, which replaced the borrowed aluminum-block Buick 215 V8 in 1964. Like Chevy's V8, the Olds V8 used an iron block, though its nickel content was higher than Chevy's blocks for greater strength. It got punched out to 350 cubes in 1968 and 403 in 1977. 350 versions used a 4.057-inch bore and 3.385-inch stroke, and unlike Chevy's V8, they always had heads of iron from the factory.

Unfortunately, Olds cranks went from forged steel to nodular iron when displacement increased to 350 cubes. Worse, in 1977, the blocks were Swiss cheesed and cast thinner to make them lighter. Portions of the main bearing bulkheads got "windows" where formerly there was cast iron. (I'm trying not to say the blocks were butchered, I really am.) You can restore some bottom-end strength by converting a windowed Olds block from two-bolt to four-bolt mains, but why? Early non-windowed blocks are a much better starting point for performance modifications. Should you insist, use four-bolt main caps with angled bolts so they don't poke into the windows.

To be fair, Chevy hasn't always made small blocks with strength in mind, either. Plenty came with puny two-bolt main caps rather than burly four-bolt caps, which are preferred for bottom-end strength. There are exceptions, like four-bolt 400 blocks being weaker than two-bolt versions, but we're speaking generalities here. Still, hot-rodders build two-bolt mouse motors to reach 500 hp, so they're not as compromised as late '70s Olds 350s. 

It's a shame, because Olds 350s started out strong. The L74 in theawesomely-named Oldsmobile Rallye 350 reached a friendly nod-worthy 310 hp, and the 1968-1970 W-31 reached 325 hp at 5,400 rpm. Burly as it was, even the W-31 was eclipsed by the 1970 Chevy 350 LT-1 with its 370 hp at 6,000 rpm.

Strangely, small and large displacement Oldsmobile V8 blocks are practically identical except for deck height. Whether you got a 455-powered 442 in 1970 or a 307-powered Custom Cruiser in 1989, the bore center spacing was 4.625 inches. Chevy V8s have to be contrarians, though; its small-block's bore centers are 4.4 inches apart while the big block's bore centers are 4.84 inches apart.

This brings us to 1977's LF9 diesel 350, which you lotrated as one of the worst engines. To Oldsmobile's credit, they didn't just take the gas 350, crank up the compression to 22.5:1, seal the spark plug holes, and call it a day. The crankshaft bearing diameters gained a half-inch of girth. Blocks were bolstered, connecting rods became beefier, and pistons got steel inserts to support the top compression ring. New heads were installed, the camshaft was upgraded to Conkerall iron, and the lifters used an exotic tungsten-titanium alloy. This wasn't enough, though.

After scores of head gasket failures, injection failures, camshafts going flat, and main bearing caps pulling loose, Oldsmobile worked to address those problems. Debuting in 1981, the new DX engine had improved gaskets, strengthened and lengthened head bolts, properly installed main cap bolts, and a roller hydraulic lifter setup. It even had a water-in-fuel sensor since the engine debuted without a water separator. But the damage to its reputation was done, and GM dumped the Olds diesel V8 in a shallow grave in 1985 just when it got good. The gas-powered 307 cube version limped on until 1990 and was still carbureted because improving that engine would have been like giving antibiotics to corpse.

Chevrolet's small-block also suffered its share of indignities. It got sidelined in favor of a Lotus-designed, Mercury Marine-built DOHC V8 for the C4 Corvette ZR-1 (which royally peeved Chevy engineers). The 400 engine got inadequate cooling and awful heads that were prone to cracking, and in 1975, versions of the 350 inside Corvettes had a shockingly paltry 165 hp. But Oldsmobile's 350 was done much dirtier on fundamental levels.