Proof You Need a Flat-Plane LS7 in Your Replica

Posted September 28, 2018

By Dean Larson

Images: eBay

Chevrolet’s line of LS engines are a fantastic option for replicas like the Factory Five GTM, Superlite SL-C and Race Car Replicas T70 and P4. They’re tough as nails, plentiful and just make too much sense in terms of horsepower per dollar. However, we just found the key to enhancing the LS with some exotic flavor in soundtrack department. As reported by Jalopnik, a seller on eBay recently listed a 2006 Z06 Corvette equipped with a flat-plane crank. The LS7 engine sounds like none other, and the seller maintains that it is indeed the only Corvette with flat-plane crank under the hood.

What’s so special about a flat-plane crank you ask? Well, for one, it’s what changes the exhaust note from chunky brute American V8 to high-strung exotic European V8, but the soundtrack is only the start, and there are real advantages for performance.

Most V-configuration engines use crossplane cranks with a 90-degree angle between crank throws. We won’t delve too deep into the physics at work here, but a flat-plane crank, with crank throws separated by 180 degrees, yields a few advantages. For one, they have a higher rev limit and rev out much faster than a crossplane crank. Flat-plane engines fire in a right bank, left bank, right bank, left bank fashion, producing a distinctive sound, but also leading to much more vibration at low speeds. The high-strung exhaust notes typical of Ferrari, Lotus and other European V8s can be credited to their flat-plane cranks.

Getting back to this Corvette and its 5.3-liter LS7, wait what? 5.3-liter LS7? That can’t be right. Well, the seller actually describes the crank as a lightweight, short-throw, flat-plane crank. We’ll go out on a limb and say the decreased stroke accounts for the lower displacement. But don’t think that dropping a couple liters robbed the LS of its claws. This beast puts down a claimed 560 hp and 450 lb-ft, up 55 hp from standard LS7 specs. Sure 20 lb-ft have escaped in the process, but this thing sings up at 8,250 rpm now!

So admittedly, it’s probably not as simple as doing a quick crank swap to get a high-pitched scream out of your standard LS engine. The engine in this Z06 is extensively modified with a full valvetrain, dry-sump oil system, camshaft, etc., etc. However, if I were doing an engine build on an exotic replica, I’d definitely at least price out a flat-plane engine. You almost have to after hearing the Vette’s pipes sing.

Or, if you’ve got a spare $35,000-plus lying around, scoop up the Z06 here on eBay and shamelessly rob its heart for your replica build. See the ad here on eBay.

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