April 29, 2021

Linkage Mag

Geared for the Automotive Life

Why a Dyno Tune Matters

The hardest part of a restoration isn’t the paint or the body. It isn’t building an engine or setting up a suspension system. 

The hardest part is the last 10% of the job. That’s when you take all the bits and pieces and make them into a whole, functional car once again.

It’s more than just assembly. Those parts and pieces have to work together in harmony, and it’s very easy for an old car to lose some of its magic to incorrect adjustments, out-of-spec restoration parts, or incorrect assembly. That X-factor — the “right” feeling — counts for a lot when it comes to usability. A car that isn’t right, no matter how good it might look, can sour the owner’s experience.

You may not even know if your car isn’t right. It’s a feeling versus a by-the-book fix, and with some older makes and models, an example that’s truly right is rare to find now that so many years have passed since they were common. It’s part of why original, unmodified cars can be worth more than restored examples — the stock, untouched example often still feels the way it’s supposed to.

But even when we’re talking about originals — and especially restorations or full custom jobs — the setup is still key. This applies to every system in your car, but for this argument, we’re just talking about the engine, which I feel is often set “close enough” and then overlooked.

It looks great, but Hemis were hard to tune even with high-octane 1960s fuel. What about now?

The world is a different place than it used to be. Fuels have changed from when most of today’s classic cars were new, and that means adjustments may need to be made to your engine to compensate. To that end, you’d be smart to find a good dyno operator and tuner to get the most out of your car’s timing and mixture setups — maybe not for full redline power runs, but for part-throttle, acceleration and cruise settings.

Setting this stuff up in your garage or mechanic’s shop is one thing, but when you’re driving your car, it’s moving and under load. That’s a different world. Reading spark plugs can tell your mechanic a lot, but even that doesn’t cover everything.

Case-in-point: This past week, I finally had the chance to get my ’79 C10 project on the rollers to see what it might do — and while the big brag-worthy numbers were the initial reason I booked a timeslot on the dyno, the actual benefit came from a place I didn’t expect.

The truck was the subject of a book I wrote on C10 modification, and the engine powering it is nowhere near stock. It’s an injected 2004 6.0L LS engine from a GMC truck, modified with “799” cylinder heads, a Lingenfelter GT-11 cam and Holley EFI. I had tuned it myself and was happy with the setup. I was hoping for 400 hp at the wheels and it eventually landed right there — but that’s peak power. The real story here is in the benefits found everywhere else.

The tuner found an additional 40 horses and about as much in torque as well thanks to a bunch of issues that became obvious while the truck was rolling — and a lot of those gains are down low in the RPM range, which makes it better to drive. It idles smoother and slower and also starts easier.

It wasn’t bad before — now it’s just optimized.

Had I not been chasing those top-end numbers, I never would have known what gains were possible where I actually use the truck, just off idle and while cruising. Those gains translate to a better experience for the driver.

The red line was the baseline for my LS engine. Note the improvement across the board (blue) from tuning on the rollers. You should apply this to your old cars.

Now, that’s in a C10 pickup with modern LS power, designed for modern fuels. What’s hiding in that restored Porsche 356? That old 289 in your Cobra? The 327 in your Corvette? Are the timing curves in each and the mixtures set up correctly for today’s gas? If you’ve never checked with the vehicle moving, how would you know?

Without taking the time to actually look, it’s just a guessing game — and one that could very easily impact the way your car feels — and by default, your perception of how these cars are supposed to be.

So, before that next long-distance drive or rally, consider an afternoon on a dyno with a competent tuner and a box full of advance weights, springs, and carburetor jets. It won’t hurt the car, and the effort could make all the difference in how that car feels out on the road.