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Over the past year, we assembled two very mild small-blocks aimed at the typical hot-rodder looking for a solid street engine built on a budget. Once both engines were assembled, HOT ROD editor John McGann suggested we test both to see how they compared, which we thought was a great idea.

In case you missed the buildups on the two engines, the first was the 355ci small-block Chevy using a 1986-and-later one-piece rear-main seal block that we built in an attempt to replicate the affordable crate engine that Chevrolet used to sell but has discontinued. We upgraded our engine with cast-iron Vortec cylinder heads and more compression.

The LS engine was a slightly different approach. It started life as a Gen-III iron 5.3-liter that was machined out to an LS1's bore size and fitted with a similar hydraulic roller camshaft. The 10.8:1 compression was higher mainly because we retained the smaller, 5.3-liter cylinder heads, which have a smaller chamber size. Both engines used dual-plane intake manifolds and the same Holley 750-cfm mechanical-secondary carburetor.

Because the small-block Chevy was originally assembled with a flat-tappet hydraulic cam, we thought the addition of a hydraulic roller cam with similar timing numbers would make this comparison a bit more fair for the little small-block. This conversion was easy since the engine we had chosen to build was a post-1986, one-piece rear-main seal block designed to employ a factory hydraulic roller camshaft.

Once that was completed, we arranged with Summit Racing to test both engines on their SuperFlow Powermark engine dyno at Trick Flow Specialties in Tallmadge, Ohio.

We elected to put the LS engine on the dyno first. After a suitable warmup and break-in time, the dyno operator, Joel Kirouac, set the timing curve to 28 degrees on the MSD ignition box and began the first of several pulls to get a horsepower and torque reading. The stock jetting on the Holley was near ideal, with an average 12.5:1 air/fuel ratio, and helped produce a peak of 419 horsepower at 6,000 rpm and peak torque of 421 lb-ft at 4,000 rpm. These were not single-run numbers but rather an average of three consecutive full-range tests.

We had decided ahead of time to drain the break-in oil and replace it with a better synthetic with the hope that we could gain an extra couple of horsepower. We chose Driven Racing Oil LS30, which is a high-quality synthetic 5W30 blend especially for LS engines. With the oil and filter replaced and the oil up to temperature, we were surprised when we picked up a solid 11 peak horsepower while also raising the torque curve throughout the entire rpm band. Our numbers for the 5.7-liter LS peaked at 430 horsepower at 6,000 rpm and 429 lb-ft of torque at 4,000 rpm, offering an excellent 2,000-rpm powerband.

This oil-change power increase was significant enough to warrant a query to our lubrication-specialist friend, Lake Speed Jr., who confirmed that the LS30's far superior base oil, along with its friction-modifier additive package, is the reason for the improvement, since the break-in oil uses none of these. We don't want to confuse anybody here; had we tested the Driven LS30 against an off-the-shelf 5W30 API oil, the power numbers would have been much closer.

With the 5.7-liter LS engine test complete, we removed the LS and replaced it with our iron-headed 355ci small-block Chevy. The engine responded with initial power numbers around 370 horsepower, which was a little disappointing. By increasing the timing to 38 degrees total, we saw a slight increase, to 378 horsepower at 5,400 rpm and 419 lb-ft of peak torque at 4,000 rpm based on the same three-run average as the LS engine test. This one did produce more than 400 lb-ft of torque at lower engine speeds, which is exactly what we'd hoped for from this mild street small-block.

The power difference between the two engines was not really breaking news. We expected the LS to be better, but were surprised that the difference was a full 59 horsepower! But before we committed the numbers, we still had to change the oil. Unfortunately, that's when the big bang happened. With the oil and filter changed, the first pull on the small-block resulted in the classic clatter and cloud of oil smoke at around 5,000 rpm. The small-block abruptly stopped and it suddenly got very quiet! The accompanying photos and captions show all the gory details.

We were not able to measure the improvement the small-block could have gained from a switch to the Driven synthetic oil, but in keeping with the LS engine's gain of another 11 horsepower and 8 lb-ft of torque, we can reasonably estimate 389 horsepower and 427 lb-ft of torque from the small-block. Though this is hardly newsworthy in today's world of 500-hp street engines, it is representative of a 355ci small-block with stock Vortec heads and a mild cam.

Another variable was the difference in compression ratio. If we assume that one point of compression is worth roughly 4 percent of power, increasing the compression on the small-block to 10.8:1 would theoretically gain 15 horsepower, which would have nudged it just over the 400-hp mark. The last point worth mentioning is that the small-block pistons employed a stock 5/64-inch ring package that included the 3/16-inch oil rings, whereas the LS was running much thinner rings. A fair test would have been to fit both engines with the same ring package to eliminate this variable.

Our test was not a complete success because one engine failed. The reason we documented our failure was so that other engine builders could learn from it and prevent this from happening to them. Despite the loss of our gallant small-block, we did show that both engines performed up to their abilities, and either would make for a great street engine. Too bad about the small-block. We had plans for this engine. Now all we can do is pick up the pieces!

We'd like to thank everyone at Trick Flow Specialties for hosting our two-engine dyno session. Dyno operator Joel Kirouac did a masterful job of keeping everything running smoothly and we want to apologize again for messing up his nice, clean dyno floor with engine oil and errant connecting-rod pieces.

We also want to thank Cory Roth, Trick Flow's Engineering and R&D Supervisor, along with manufacturing engineer Dan Monegan. Big thanks also go to Summit's chief marketing officer Al Noe and product development master Brian Nutter for their help and the tour of Summit Racing's main Tallmadge, Ohio, facility. It was very impressive!

Lobe separation angle: 112+2

*The peak and average numbers were from the entire pull with data taken at every 100 rpm; this chart reveals data from every 200 rpm.

On episode 24 of Engine Masters, the team explores one of the most-asked tech questions: What budget bolt-ons can be used on a stock small-block Chevy 5.7 to get more horsepower? Watch as David Freiburger, Steve Dulcich, and Steve Brule take the cheapest Chevy 350 crate engine you can buy and make mods that gain nearly 130 horsepower! It's a dyno-proven, easy-to-install power combo that will give you the best bang for your buck. Sign up for a free trial to MotorTrend+ today and start watching every episode of Engine Masters, plus much more!