Dyno Testing A Modernized C3-Headed 358-Inch Vintage Cup Engine

You might remember an article from this past summer, where Lake Speed, Jr. dyno tested his dad’s vintage 358 cubic-inch Cup engine from the 1990s, only to find that the engine was way down on power. After some significant searching, a few key issues were identified, but rather than just fix them and move on, Speed decided to see how far he could push the engine with modern technology, while still keeping the engine true to its early form.

That means not messing with the vintage C3 heads too much, not changing the stroke, and generally keeping it as “original” as possible, while trying to make way more than 480 horsepower. Speed had a number in mind at the outset, which wasn’t publicly disclosed, but behind closed doors was revealed to be both lofty and achievable (on paper) at the same time.

Bringing It Back Up To Snuff

That led to quite a few companies getting involved to bring this engine squarely into the 21st century, while still using late 20th-century (I know, I know… I hate that term too) components. Our friend Billy Godbold dreamed up a modern profile for a new COMP Cams camshaft, CP Pistons whipped up some pistons to get the compression back, and Total Seal tossed in some proven 0.7mm piston ring technology to ensure all the combustion and engine oil stays where it’s supposed to with a minimum of drag.

Two of the modernized parts of this engine rebuild were a modern camshaft profile and the hone, specific to the rings being used. There has been a lot of development in the past 25 years in both fields, and significant power can be found simply through optimization alone.

The vintage R block was honed by Pro Stock legend Greg Anderson himself with incredibly modern materials and techniques and Pro Motor Engines went through and brought the C3 heads and intake manifold to tip-top shape, as well as assembling the engine with the utmost precision. The team was able to reuse the original block, crank, rods, cylinder heads, intake manifold and oil pan — keeping the engine authentic to its roots.

During the reassembly process, PME’s Dennis Borem discovered that the oil pan on the engine was fitted with oil squirters, albeit deactivated ones. “I didn’t look at the pan until we were ready to start mocking everything up for reassembly, and I realized it has sprayers in it,” says Borem. There were no lines fitted to it, and no provisions in the block to provide oil to the sprayers, so they were never active on this engine. We got it plumbed up and working again, as well as adding a pickup for right-hand turns, since this will be a road-racing application.”

Besides the head, block, crank and rods, the original oil pan and intake manifold were also reused. The C3 intake manifold had the runners opened up a bit to match some of the cleanup done on the C3 head's intake ports, as well as a little bit of reworking in the plenum area using knowledge gained over the past couple of decades building competitive Cup engines. The oil pan has built-in oil squirters from the start, but they weren't hooked up. PME plumbed them in and got them functioning on the engine for this iteration.

Getting It On The Dyno

To break in the vintage engine on the dyno and make some early power pulls, the PME team used Sunoco E15 unleaded gasoline which is the current NASCAR spec fuel. However, waiting in the wings was a big blue can of some VP Q16. With the engine ready to go, the first couple of pulls were easy sweeps. The dyno showed 761 horsepower on the screen, with the unleaded gas and break-in oil still in it. That number alone well surpassed the quiet goal that was only uttered in confidence months prior, and equates to a stout 2.12 horsepower-per-cubic-inch.

But the team wasn’t done there. Besides having a better fuel to test, there was the issue of getting a proper carburetor on the engine. The old, used carb on the engine was still good, obviously, but this engine deserved better than good. For that, Lake went to Bill Pink for a proper carburetor, and it was time to swap that on. The peak numbers remained the same, but there was about a five-horsepower increase across the board, with a bit stronger increase around 5,500 RPM.

cup engine on the dyno

The Bill Pink carburetor didn’t add any peak power, but definitely brought the curve up from 5,500 rpm onward.

Then switching to the VP Racing Q16 fuel, another 10 horsepower, both peak and across the curve, were found for 770 horsepower. From there the break-in oil was drained and Joe Gibbs Racing 0W-16 oil was poured into the engine. “This oil should be worth about four horsepower on this engine,” says Speed, Jr. “We also made a jet change, so this might not be totally accurate.”

The final pull showed 779 horsepower — or 2.17 hp/ci — from this vintage race engine, completing this incredible project. So, to recap, that is an 18 horsepower increase from start to finish on dyno day from Q16 and 0W-16 oil. That is an 89 horsepower increase from when the engine was in its absolute prime back in the ‘90s (690 horsepower when it went out the door, originally), meaning modern technology accounted for a 13.1-percent increase in power.

The big increase, however, is from the power it made when it was pulled out of the car and tested earlier this year. There, it only made 480 horsepower. A number so low, it kicked off this whole project. From that dyno session, the engine picked up 300 horsepower, or a 62.5-percent increase. It’s pretty impressive what a little bit of technology and know-how can account for on the dyno.

final cup dyno

Here you can see the difference just between the first and last dyno pull of the day. 19 horsepower from just Q16 fuel and switching from break-in oil. The real gains are the ones realized between the original dyno when the engine was new (690 horsepower), the dyno last summer (480 horsepower) and the final dyno at PME (780 horsepower). That shows just how capable PME is at building a good-performing engine, regardless of its vintage.

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Greg Acosta

Greg has spent eighteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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