S471 Twin-Turbo 540 cid Big Block Chevy Engine - Engine Builder Magazine

S471 Twin-Turbo 540 cid Big Block Chevy Engine

We can all relate to 650 horsepower eventually becoming boring. That was why Zack Gillespie decided to move from a naturally aspirated big block Chevy engine to a twin-turbo 540 cid big block Chevy capable of four-digit horsepower. Check it out!

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Any opportunity we have to see hundreds of hot rods, racecars and cool vehicles in one spot, we usually take. As such, we were recently at the Piston Powered Autorama in Cleveland where we came across a number of intriguing cars. One of them was Zack Gillespie’s 1970 Chevelle with a twin-turbo big block Chevy engine stuffed in it.

We found out that Zack got this 1970 Chevelle about eight years ago, and in that time, he has had four different engine combinations in it. The newest engine under the hood of his Chevelle is a 540 cubic inch Chevy engine that features a Dart block, a Callies Magnum crank, Oliver rods, Wisco custom-coated pistons, a Plazmaman intake, Injector Dynamics 2000 injectors, twin BorgWarner S471 turbos done by Work Turbochargers, and a set of custom headers.

Up top, the big block Chevy features a set of AFR 305 heads, which Gillespie hinted were on the small side, so he had the heads machined out to 317. He also opted to change out the exhaust valves and went with a custom COMP Cams camshaft to control the valvetrain.

According to Gillespie, Winter Performance & Machine did the head work, and Zack’s desire to move from his previous naturally aspirated big block Chevy to a twin-turbo set up came about seven years ago when he went to Drag Week.

“When I went to Drag Week out here at Summit Motorsports Park in Norwalk, OH, I saw other guys who were running big block turbos, and I wanted to have one of those some day,” Gillespie says. “Seven years later, the car has been down for about a year getting all the work done. The body came off the frame and all of that.

“My last engine, when it was on the dyno, made 650 horsepower and 638 ft.-lbs. of torque. I don’t know how, but that got kind of boring. I decided to throw turbos on it and initially I was just going to turbo the last engine. Then, I went down the rabbit hole. I changed up the rear end to a TRZ housing with Strange components and a Rossler TH400 transmission. It’s more or less a racecar that I’ll use mostly on the street.”

The Plazmaman intake on top is a nice piece of functional artwork, but Zack was trying to not have to modify the Chevelle’s stock hood. Lo and behold, the intake needed extra room.

“I went with the Plazmaman thinking I was going to have enough hood clearance to be able to shut the hood and not have to cut it, but I ended up having to cut the hood anyways,” he says. “It is what it is, especially when you’re modifying things. My friends over at Muffler Boss Auto Care in Northfield, OH helped me out and they’re the ones who cut the hood for me. They also modified the hot and cold side for me as well.”

Looking for four-digit horsepower, Zack says he plans to enjoy the car with his family, and maybe a drag-n-drive event in the future.

“I’ll keep the boost low and just enjoy it,” he says. “I’ve got two young boys and a wife and we all like to cruise. Hopefully, this engine combo will be the last one and I’ll be content with everything and have more than enough room to grow.

“The engine should handle over 2,000 hp, if I wanted it. The turbos will be limited around 1,800-hp crank. I want to see four figures on a dyno, which should be easy to accomplish with low boost and then back it off and cruise it. I’ll get a cage and everything in it and hopefully I can run it at the track and put down some times.”

Zack’s big block Chevy is controlled by a Holley Dominator, so he can have multiple tunes on hand for the street and the track. All in all, Zack did his build the right way and the work has paid off. Hopefully, he gets to have some fun with the revamped Chevelle this summer.

Engine of the Week is sponsored by PennGrade Motor OilElring – Das Original 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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