Newly Minted ‘Vette Owner Compares LS V8 to Rotary Engine
Newly Minted ‘Vette Owner Compares LS V8 to Rotary Engine
Before the insanity begins, YouTuber Rob Dahm explains his choice of swapping in a rotary by comparing it to the LS6.
Usually, when someone has a Mazda RX-7 and needs more power and less hassle than the stock rotary motor, they’ll drop in an LS or LT. The results are quite successful, and are a big improvement over the status quo.
Not Rob Dahm. He recently purchased a busted C5 Z06 with the intent of swapping the trashed LS with a fresh-ish rotary engine. Today, he explains the decision by comparing the two’s differences in weight and size.
“When we first announced the rotary Corvette, there was a lot of controversy,” said Dahm, “as there should be. The whole point that we wanted to do was not just to be controversial just to be controversial, but give you a talking point, something that’s kind of interesting, unique but useful.”
Rather than focus on the usual horsepower comparisons, though, Dahm decides to pull out his measuring tape (and all of his cars’ rotary engines) to support those who want to swap in either a rotary or an LS/LT.
“In the sense of size, this 13B is not much larger than the diameter of the flywheel itself,” said Dahm. “You look at it from the center of the eccentric shaft. The flywheel is about six and a half inches in radius, and really, that’s the height of the motor, at least for the short block.”
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As far as the depth goes, it’s also 6.5 inches from the eccentric shaft, most of which is the oil pan, which rotary engines need a lot of. Meanwhile, the height is 15.5 inches from the shaft, due in part to the space needed for the hoses running between the block and the intake back in the day.
“This is where this engine really comes up with its advantage,” said Dahm. “It’s the length of the motor. A two-rotor is such a baby motor, and really, twelve and a half inches is the core of the motor.”
With the first pulley and the flywheel sandwiching the rotary, the total length comes to 19 inches. The total height with everything on is 25 inches. Dahm says that despite the compactness of the engine, the stock engine mounts add to the width. Of course, Dahm plans to put his rotary into a Z06, so things could go wider still.
“At first glance, it’s very apparent [that] this is a larger engine,” says Dahm of the LS6. “Physically, it is much bigger. A quick measurement of the flywheel confirms that, [as it’s] closer to seven and a half inches. This is already a bigger vehicle.”
From the LS6’s eccentric shaft to the intake manifold, the height comes to 17.5 inches, while from the shaft to the slimmer oil pan, it’s only 7.5 inches. The width from center is around nine inches on either side, 21 inches from head to head. Thus, any transplants are going to need plenty of room to accommodate all of that displacement, for which there is no replacement.
“The serious advantage this block [has] over a rotary engine is [the intake manifold],” said Dahm. “[It] is much smaller and much more compact, and really built into the area of the motor that is dead space. It is also made out of plastic, which means that a longer form of this block weighs much less than adding the components of the rotary engine.”
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And while the LS6’s total height is the same as the 13B’s, Dahm says the former starts losing more advantages when the exhaust manifolds are installed, adding at least three more inches on each side. Additionally, the stock engine mounts bring more inches to the width at the bottom of the block, while their positioning helps to keep things balanced.
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“Right here is the most controversial, apples-to-apples comparison that you can do with [the LS6],” said Dahm. “We’re gonna weigh the short block compared to the [13B].”
With the use of a fragile bathroom scale, Dahm carefully sets down the LS6, pulling a weight of 384 pounds. The 13B receives two measures, though: one with, and one without, the intake manifold and water system. Minus the required bits, the 13B comes in at “a healthy 200 pounds exactly.” With them on, it’s around 232 pounds.
Of course, Dahm admits that to make the 13B as powerful as the LS6, turbocharging and piping will be needed. This is going to be one interesting Z06 build.
