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Engine of the Week

Blown 598 Big Block Chevy Engine

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While soaking up the sunshine of Bradenton, FL during Sick Week, we were also soaking up a lot of awesome street-legal drag cars. Perhaps one of our favorites of the week was Royce Payton’s 1965 GT350 Mustang with a blown 598 big block Chevy engine. It’s one of those cars that looks as good as it sounds and vice versa. We had to know more, so we caught up with Royce after his day 1 pass at Bradenton Motorsports Park.


Royce and his Mustang were among the A group (faster than 8.49) competitors, and Royce was competing in the Unlimited Iron class. He turned in a day 1 time slip of [email protected] mph – something he hoped to improve on. While the ETs could improve, the car itself looked absolutely stunning, and this Mustang has come a long way to get there.

“It was a very rough car when we got it,” Payton says. “That’s usually how all race cars start out. We did the paint and body work on it, and some friends of mine helped do the cage and stuff like that. We built it in 2008, and it’s been a work in progress since. It’s had kind of a rough life because we beat on it quite a bit.”

Royce owns Custom Design Paint and Body Work in Fort Collins, CO. Over the years, he’s used the 1965 Mustang for different racing disciplines, and the big block Chevy engine was mechanically injected when Royce first built the car as a door car for heads up racing. It wasn’t until a friend got him into the drag-and-drive scene that the car underwent some of the changes you see today.

“A friend of mine, Matt Frost, who puts on Rocky Mountain Race Week, got us interested in competing in his event, so we started building the car to have more street driving abilities,” Payton says. “We switched over to Holley EFI. It’s got a Dominator on it. We put all that on in 2014 and we’ve been working with it ever since.”

Payton’s 598 cubic inch big block Chevy engine runs blown injected alcohol thanks to the help of a 14-71 high-helix blower. The engine also features a Crower valvetrain, a Steve Morris camshaft, Brodix BB3 Xtra cylinder heads, and Mahle pistons.


“We just try to keep it together,” Payton admits. “It’s kind of a monster, but overall, we have a pretty basic setup for a blown car. There’s not a whole lot of secrets in it. We just turn a big puffer on top of it.”

Aside from the what’s in the engine, the Mustang also boasts a Bruno converter drive with a three-speed Lenco trans and a Gear Vendor overdrive on the back.

Royce has never put the car on a hub dyno, so he’s unsure of an exact horsepower figure for the 598 BBC, but based on fuel consumption, he estimates it makes right around 2,500 horse. And, when the Mustang is done flying down the dragstrip, Royce does a few things to prep it for the streets.

“We actually swap the blower from street to strip,” he says. “It’s a strip blower and that doesn’t work very good on the street – it’ll meltdown. We also change our fuel. We run alcohol on the dragstrip and then we switch over to whatever we can get for pump gas. In Colorado, we have 91 octane, but here in Florida we can use 93 octane, so that’s been nice.”

Being out in Colorado, Royce and his blown Mustang are also used to much different air, especially when compared to the air in Florida. That proved to be a factor during Sick Week.

“We’re struggling a little bit because we’re trying to slow the blower down, so we don’t make so much boost because we are running out of injector at Bradenton,” he told us. “We slowed it down from what we did yesterday (during testing) and we still made just as much boost, so we’re struggling. We’re trying to keep it from melting down. I think we’re right on the edge of hurting it, which we don’t want to do. We’re trying to make it live.

“We’ll push those limits on Friday, but not on Monday. On the track, we’re shooting to get as close to 7.50s as we can and try to keep it safe all week. Then, later in the week, we’ll probably wake it up and see what it’ll do if we can find injector for it. Right now, we’re just going to run it just past the eighth and click it off and try to get a safe number.”

After his day 1 run of 8.632 in the 1/4-mile, Royce recorded ETs of [email protected] mph, [email protected] mph, and [email protected] mph, for an average of [email protected] mph during his Sick Week, which put among the finishers and in 9th place in Unlimited Iron. He’ll try to improve on those ETs later this year, but there’s no denying this is one badass, big block Chevy-powered Mustang!

Engine of the Week is sponsored by PennGrade Motor OilElring – Das Original, Scat Crankshafts and Engine & Performance Warehouse Inc./NPW Companies. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at [email protected]

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