Chevy Small Block Testing - Legendary Small-Block Shootout

We Pit The DZ302 Vs L76 327 Vs LT-1 350 In A No-Holds-Barred, Dyno Dogfight.

From the September, 2009 issue of Super Chevy
By Richard Holdener
Photography by Richard Holdener

Link to Origional Article

If you have even an ounce of Bow Tie blood, you will immediately recognize the three names presented above as nothing less than legendary small-blocks. During the muscle car era of the '60s and early '70s, this trio carried the torch into battle for their respective displacements. Sure, the fuel-injected version of the 327 was rated 10 hp higher than the carbureted L76, but both shared the same internal components.

The DZ302 came about because of the need to produce a 5.0L displacement powerplant for the popular SCCA Trans-Am sedan racing series. The LT-1 350 represented the last hurrah for the high-squeeze, solid-lifter small-blocks, as the '71 version made due with just 9.0:1 compression compared to 11.0:1 for the 1970 model.

We all know now that the power ratings in the old days were somewhat suspect. The manufacturers played games with the official power ratings in order to appease the buying public, insurance companies and racing officials alike. Offering their engines with elevated ratings was not uncommon, as horsepower sold cars and with the lack of available dynos to verify the claims, it was difficult to tell the difference between a 350hp engine and one rated at 370hp.

Speaking of ratings, it is also important to note that these differed wildly from those used today by the OEMs. Where the new LS3 small-blocks are tested to the latest SAE net (flywheel) standards and are rated with full accessories, exhaust and the factory induction system (basically the way it comes in the car), pre-1972 engines were rated in optimized condition sans accessories (open dyno headers, no accessories, no air inlet restrictions, etc.). What this means is that a 370hp LT-1 from 1970 is actually much closer in actual power output to the 300hp LT1 circa 1995.

Regardless of the differences in the power ratings, what we really wanted to know was just how each of these legendary small-blocks compared to each other. Was the output of the high-winding 302 really closer to the often-touted 400hp than the rated 290 hp? Was the 365hp 327 more than a match for the later 370hp LT-1 350? After all, both the 302 and 327 shared slightly wilder cam timing than the LT-1, but would the milder cam timing offset the additional displacement? Would the shorter stroke small-blocks make more peak power than the long-stroke 350? These were all questions that deserved answers and these answers had to come from more than the recollection of some racer who ran one back in the day.

This is one of those times when a simple session of bench racing snowballs into a monster of a dyno project. Obviously, the only definitive answer had to come from the dyno. Real back-to-back testing was the only surefire way to provide not just peak power numbers for each, but overall power curves. After all, man does not live by peak power alone. It is the average power production that provides the key to a successful street powerplant, and since all three of these production small-blocks were indeed street motors, we needed to test them.

Testing three legendary engines meant building three legendary small-blocks. Luckily for us it was unnecessary to reproduce the motors down to the last casting number. Basically all we needed to do was pay close attention to the engine specs of each and duplicate these where necessary. There were a few mandatory items in each build up, namely things like 11.0:1 compression, the proper cam specs (duplicates of the original) and original big-valve "fuelie" cylinder heads. While each of the motors was adorned with different casting numbers, the reality is that the big-valve performance heads were much more alike than different.