Naturally Aspirated 540 cid Big Block Chevy Engine - Engine Builder Magazine

Naturally Aspirated 540 cid Big Block Chevy Engine

After having issues with an engine built elsewhere, a customer came to H Squared Racing Engines to build him a streetcar combo. Utilizing an existing block and crank, H Squared was given the freedom to spec the rest of the engine. Check out the result!

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During a recent trip to Houston, TX for the PERA Conference, the Engine Builder team had a few extra days to visit some local shops. Trying to escape the 90-plus-degree heat hanging around from the end of summer, we took refuge at H Squared Racing Engines, where we visited our old pal Halston Harrist, who was featured in our Engine of the Week series back in 2019.

Big Block Chevy
540 cid big block Chevy engine

We not only got to tour the engine and machine shop that opened in 2010, but we got to see a few engines Halston had in progress, including this naturally aspirated 540 cubic inch big block Chevy engine.

“A good customer of ours had a friend who had an engine built by somebody else and he was having problems with it, and it didn’t have any compression at all,” Harrist says about the engine build coming to H Squared. “He brought it to us, we tore it apart, found a few little things here and there and told him what we needed to do, so he let us run with it. He said build it the way you would want to build it, and that’s what we did.”

big block Chevy engine
The engine was built for a ’69 Camaro.

The customer gave H Squared his block and crank and it was up to Halston and his team to do the rest of the engine combo.

“We spec’d out his pistons, rods, heads, and camshaft – all the way up to the induction,” Harrist pointed out. “The goal was to make about 700 or more horsepower to go in an old ‘69 Camaro. We actually ended up making a little over 800 horsepower. We spec’d this whole thing out to run on pump gas.”

Since the engine was going in a streetcar and would be naturally aspirated, one of the important parts was the carburetor. H Squared decided to run a 4500 series carburetor from Pro Systems.

Pro Systems carburetor
The intake was modified to fit the 4500 series carb from Pro Systems.

“It’s called a Little Monster, but it’s on a 4150 base, so we had to modify the intake a lot,” he says. “When we put this on here first, the butterflies would just run into the intake, so we had to open up the intake manifold to even run the carburetor. The intake was based on something the customer already had. We knew it was a good intake to run, so we weren’t worried about it, but we wanted more induction. It’s a big motor, so we wanted the air. We wanted a 4500 carburetor on it and he was adamant about trying to run this intake manifold and didn’t want to raise anything up higher, so we made it work. That’s when we reached out to Pro Systems and they make this specifically to run on a 4150 intake manifold and it worked great.”

While the intake required some modifying, that wasn’t the only machine work done to the big block Chevy. In fact, H Squared gave the engine the full rundown of machine work any engine would receive.

big block Chevy engine

“Every engine we do, no matter what, we’re going to check what I call the three main machining processes,” Harrist says. “That’s the align hone where the crank sits, we’ll torque plate hone the cylinders and we’ll deck it. We set his deck height to put his pistons where we want and to help the compression. Then, we hone the cylinders with a torque plate. These are at a 4.530” bore on the final bore size and it’s a 4.250” stroke.

“It’s got a good set of Wiseco pistons, some Scat rods and a Scat crankshaft. We balance everything together so it is all internally balanced and it’s set up for just around 10.5:1 compression, and good to run pump gas.”

big block Chevy engine

The base of this 540 cid big block Chevy is an OE GM gen VI block, which has a one-piece rear main seal. It’s what came in some of the later model EFI big block Chevy engines on some of the heavy-duty trucks.

In addition to the carb, intake and the rotating assembly, the big block Chevy features a hydraulic roller setup with a bunch of COMP Cams valvetrain componentry. Housing that valvetrain are a pair of AFR cylinder heads.

big block Chevy engine

“We like rigid valvetrain, so it’s got a set of stainless steel COMP Cams Ultra Pro Magnum rockers on it,” he says. “We actually upgraded to 7/16ths one-piece Trend pushrods. We really wanted this to spin as much rpm as it could, so it’s got a bigger pushrod than most engines you’ll see out there. It’s got nice, steel rockers. It’s got a hydraulic roller COMP Cams camshaft that has a 248 duration at .050 on the intake and 258 duration at .050 on the exhaust. It’s 111-degree lobe separation and we’re approaching .700 valve lift on intake and exhaust. But it is hydraulic and we put this on the engine dyno and spun it out to about 7,200 rpm with no problems. We also have a COMP Cams billet timing set and timing cover.”

Helping to keep all these components running right is a wet sump oiling system featuring a Melling internal high-volume pump. All that’s left to do on this engine is install it in the customer’s 1969 Camaro.

big block Chevy engine

“I can’t wait until he gets it in there,” Harrist admits. “He said he’s going to come give me a ride in it, which will be nice. It’s a streetcar engine, hydraulic roller on pump gas. It wasn’t really dedicated to go race, but he could probably go to the track and move up on some people who did build something to go race. It’s just a nice piece, and he let us do what we wanted to. If I had to build an engine for my personal toy, I would want something like this.”

With 800-plus horsepower on hand, it’s nothing to sneeze at, especially when you consider there’s no boost from this naturally aspirated build.

Engine of the Week is sponsored by PennGrade1Elring – Das Original and 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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