This LS-Swapped, Compound Turbocharged Trans Am Is An Exercise In Home-Fabbed Ingenuity

10 min read

This LS-Swapped, Compound Turbocharged Trans Am Is An Exercise In Home-Fabbed Ingenuity

10 min read

“I remember looking at the engine bay and thinking, ‘If I try to make this perfect, it’s never going to get done,’” recalls Timothy Ball. “And that’s when I started stacking the piping.”

A wireline operator from Peyton, Colorado, Ball is not the kind of person who will let conventional wisdom get in the way of a good idea. Growing up, his wrenching exploits involved diesel trucks, American muscle, and air-cooled VWs in nearly equal measure, which in turn provided him with a wide-ranging perspective on how to build power.

“Compound turbos compound the problems,” he jokes. “But I wanted this Pontiac to have some personality. It’s kind of a rat rod right now, and that can be polarizing in a way. You’ve got the purists who are like, ‘Why would you do this to a Trans Am?’ And then you’ve got the people who love this Trans Am because you never really see them built this way.”

Before we dive into the particulars, we should probably give you a crash course on how a compound turbo setup works. Most often seen in diesel applications, compound setups involve two turbos, usually of different sizes, arranged in series. Air enters the system through a low-pressure turbo. At low RPMs, this turbo – is typically the larger of the two – usually doesn’t make boost, and instead sends the airflow into the smaller, high-pressure turbo, which then produces the low RPM boost. As the RPMs ramp up, the low-pressure turbo spins faster, creates its own boost, and then feeds that into the high-pressure turbo to be compressed a second time, in turn compounding the boost pressure that the turbos make.

Is it the easiest way to make power with a boosted LS? Absolutely not. But is it cool? Hell yeah it is. And for Ball, it was a great way to put his inventiveness to the test.

“I think this era of the Firebird is an icon for its time – sort of the last of that generation of hot rods,” Ball says. “When I got it I had aspirations of starting my own business, and I thought it would be a good flip. But it ended up having way more rust than I expected, so I initially focused on the bodywork, and then I started going through the non-original 400ci block that was in it. I just wasn’t really satisfied with the power that the V8 was making, and I realized I could probably put together a pretty stout LS for it for less money than I would spend trying to build up the 400 to make the same power.”

He then set to work getting a modernized powerplant in the engine bay, first sourcing a 5.3-liter LS from a junkyard, which he ran naturally aspirated with the intention of eventually adding boost to the mix. “I wanted to set up everything for turbo so it would be an easy transition, but with the Covid shutdowns and stuff, it ended up being a really slow process.”

That engine met its untimely death not long after, when Ball windowed the block during a local burnout competition last year, but he had a backup plan waiting in the wings. “I had already picked up another 5.3-liter LS, which was a Gen IV rather than a Gen III, so I started doing that swap. LS Fest West on my mind at that point, and I decided I was going to get the Firebird there one way or another. But I also really wanted the turbos on it for the event.”

Although he had planned to run the turbos below the hood line, Ball knew that putting together the plumbing required to make it work would be an involved process, and time wasn’t on his side. “So I thought about what would be the easiest way to run all this piping, and that’s when I started stacking it up.”

Outfitted with a custom-fabricated manifold of Ball’s own design, the forced induction setup consists of a GT45-style turbo and a smaller T3/T4 Hybrid-style snail. “The intake runs into the big turbo first, and then out of the big turbo into the smaller one, then out of the smaller turbo into the air-to-air intercooler and into the motor,” he explains. “So the intake is basically piped backwards from the exhaust.”

He says that his butt dyno indicates the LS is making somewhere in the neighborhood of 600hp at the moment, though its full potential hasn’t really been realized as of yet. “That bigger turbo is probably good for 800hp on its own,” he notes. “Right now I’m working on the tuning – how the waste gates are set up makes a big difference in the power delivery.”

Refining the setup can be a lengthy process, but he notes that the Holley Terminator X EFI system he chose for engine management was instrumental in getting the car up and running in time to race at this year’s event. “I’d been researching LS swap stuff, and when the Terminator X came out, it really caught my attention. There’s a lot of bang for the buck here. It’s also really easy to navigate, and there’s just a ton of great online resources for information now for just about any kind of setup you want to do.”

Ball made it to LS Fest and managed to fire off a couple of passes over the weekend, including one where he was lined up against Emelia Hartford in her twin-turbocharged Buick Regal. “That was a surprise to me,” he says. “I got her off the line, but I didn’t hold that lead for long.”

Compound Turbo T/A vs. Hartford Regal

Compound Turbo T/A LS West 2021

Photo: Evan Perkins

With some extra time to spare now, Ball is already in the process of getting the Pontiac ready for next year’s event. “Over the past few months I’ve been building a 408ci LQ4 bottom end with a Molnar crank and rods, and forged pistons,” he says. “That’s in the car now. It’s also running on E85, and I’ve been tinkering with the turbo setup to get everything dialed in the way I want it. The game plan is take the compression down, control the boost a bit better, and start strategically working my way up to bigger power. I think that might work out better than just going all-out and sort of hoping for the best, like I did at this year’s event! But either way I’ll just be happy to be there. I’d rather be wrenching in the pits at LS Fest than sitting on the couch at home.”


Bradley Iger
136 Posts


Larry Chen
35 Posts