• Aug 19, 2007
Here's another example of liking the individual hardware pieces, but being repulsed by the idea of the ultimate combination. RX7s are cool. Grand Nationals are cool. But a vehicular mash-up of a 1993 RX-7 powered by a Buick GN's V6 seems a little weird. Weird to think that it even gets past regulatory agencies, as it's an older, totally alien engine in a newer car, which might make it interesting to register in a state with California emissions. The swap is well done, though, even if we'd question the handling a heavier and much more powerful engine in the snout brings with it. It's fast, but does it understeer like a pig and snap the tail out? The seller seems to have focused on posting low elapsed times in the quarter mile, so think about that when you conjure what the dynamics may be. Follow the jump for more.

[Source: eBay via Carscoop]




3rd-generation RX-7's are not only the zenith of the model's performance abilities, they're also the end of the line (so far) for the 2-door Wankel sports car. Turbo models were fitted with a staged turbocharger system that used two different compressors to boost power across the entire rev range. It was effective in stock trim, though it's less than celebrated by the crowd that likes to tweak on their 7s. Grand Nationals, too, were the baddest of badass A/G body GMs. The 231 V6 with a Garrett snail hung off the front was impressive in stock form, is capable of silly-to-ridiculous power levels when fiddled with, and still returns reasonable fuel mileage,which mirrors the seller's claim. As much as we recoiled at the initial thought of this particular swap, the car is obviously fussed over. Shoot, it's got a Dana 44 rear from a Viper for crying out loud, and it is an appropriate shade of GN black. Gather something north of 16 grand together and bid away!


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    • 1 Second Ago
  • 42 Comments
      • 7 Years Ago
      While they're both good cars in their own right. The best engine swap I've ever seen done for the rx7 was with the 3 litre turbo supra engine, the finished product was called the supra 7 by sp engineering.
        • 7 Years Ago
        A 2JZGTE is hardly the 'best' swap for any car. It's a big iron block for one thing, and once you get into the higher power levels it becomes nothing but a drag slut or dyno queen, since it has no power down low thanks to incredible lag. I mean come on, the engine alone sans-trans is ~600 pounds, and with the six-speed attached to it, it's ~740 pounds! An LS1 complete with transmission is only ~500 pounds.
        • 7 Years Ago
        One of the best I've seen, not one of the best I've imagined.
      • 7 Years Ago
      the car's ruined
      i dun have the funds to maintain a twin turbo rotary
      but if i did, i'd definitely pick a rotary over a V6 or any piston engine, no matter who built it.

      no seriously... the car's been ruined.
      put the rotary back in that thing
      • 7 Years Ago
      @Mike

      Rotary's don't suck, not all people like low tec 7liter V8 truck engine's.
        • 7 Years Ago
        Or idiot fanboys just don't like to admit that a 'low-tech' lump of American metal is better than the rotary...Maybe? Let's see, a V8 that has more power naturally aspirated than a twin-turbo rotary, is more reliable, more durable, weighs the same if not less, and is more efficient both with fuel and oil, all while still being able to rev to ~7,000 RPM, handle forced induction into quadruple digit horsepower, and provide a more livable power band...Where is the rotary better again?
        • 7 Years Ago
        787b, maybe go re-read the post I replied to. Every comment I made was referring to the "V8 truck engines" mentioned in said post, not the Buick engine (since that wasn't mentioned).

        As far as RPM are concerned, a modern SBC is capable of surpassing 8,000 RPM when built right, but in lesser forms there really isn't any need to do so, since 6,500-7,000 will suffice just fine in most any situation, especially considering there is ample power all the way through the rev range (unlike the rotary).

        Really though, your old NA rotary has no bearing on anything in this thread, since the car in question came with a TT 13B, not a 12A. And in the case of durability this is a rather significant point, since as you have said, the NA rotaries are pretty solid, but once you introduce FI, that all goes out the window.
        • 7 Years Ago
        Nick, I just ran the Carfax on this car. It appears it went 117,000 miles on the ORIGINAL engine, then was wrecked in 2004. Our eBay seller bought it, brought it to Florida in 2005 and did the conversion, and has barely put 1000 miles on it since. So I'm not sure how 117,000 miles isn't "durable".

        As for RPM's: "a modern SBC is capable of surpassing 8,000 RPM when built right". Well, a rotary can turn 8,000 BOG FACTORY STOCK. In fact, the latest rotary has a 9,000 RPM red line FACTORY STOCK. A mildly "built right" rotary will go North of 10,000 RPM without breathing hard. The limiting factor is clutches and transmissions to handle it.

        "especially considering there is ample power all the way through the rev range (unlike the rotary)" Wrong. The rotary has a far flatter torque curve, and a smooth, linear horsepower curve. The piston engine curves both peak and decline somewhat quickly.

        What gives people the wrongheaded idea that you have is that the they don't have the big numbers of the big V8's, and people who are scared of RPM's because they are used to truck engines don't drive them high enough in the RPM range. If you drive a rotary below 2000 RPM, it will not be any fun. If you stick to 6000 to 8000; endless fun.

      • 7 Years Ago
      In Grand American racing, Mazda runs a three-rotor 20B, and even with equalization, the car still has difficulty keeping up with an LS2 in a larger car.

      http://www.huliq.com/438/mazdaspeed-motorsports-and-speedsource-announce-full-season-2007

      I like rotaries. I love to hear the RX-8 run in Grand Am. The motor sounds amazing. But on pure power or power to weight, the V8 is the clear winner.

      Yeah, you can modify the rotary to be lighter. You can modify a V8 too. And the V8 is also cheaper.
      • 7 Years Ago
      What kind of idiot thinks a buick v6 is better than a twin turbo 13B.
        • 7 Years Ago
        What a waste of a perfectly good Grand National engine.
        • 7 Years Ago
        Apparently you've never driven a turbo buick.
      • 7 Years Ago
      lol Stephan, your ignorance amuses me, why don't you actually read a few posts up that somebody posted about the ls engines? They're anything but what you said.
      • 7 Years Ago
      The circle racing is for some people. I wont ridicule it. To each his own I guess
      • 7 Years Ago
      i like rotaries. i realise that for a lot of people an Ls1 would be a much better engine, but hell get a used C5 corvette!
      as for the buick V6, i'm with everyobe else, rotary or at least an ls1 please... stick the V6 in a nice sleeper buick :D
      • 7 Years Ago
      Ebay has some strange auctions that's for sure http://hauntedebayitems.blogspot.com/
        • 7 Years Ago
        Here is something more for you naysayers to chew on: Mazda won the overall at the Le Mans 24 Hours in 1991 with this engine you all claim is so unreliable.
        You can quote me on that and go look it up if you like.
      • 7 Years Ago
      According to Autotrader, the 05 Grand Prix GTP with a supercharged cast iron 3.8 weighs 3583 lbs while an 05 Grand Prix GXP with an aluminum 5.3 V8 weighs 3600 lbs.

      I believe they both use GM's 4t65e trans, but I could be wrong.

      Since an intercooled turbo will be heavier than the GTP's supercharger, I'd guess that the Buick 3.8 in this RX7 will have a slight weight penalty over an LSx.
        • 7 Years Ago
        You're basing the weight of a 20 year old engine on the curb weight of an entire brand new car? Great stuff.
        • 7 Years Ago
        I realize there is room for error. And if anyone has better weight data, I hope he/she speaks up.

        The GXP and GTP are nearly identical aside from the engine, so I thought it would be a pretty good indication of the relative engine weights.
        • 7 Years Ago
        The LS1/6 are aluminum block engines. The Buick 3.8 is cast iron. But it is smaller. The stupid Mazda automatic is a frickin' tank, so going to the 200 4R will definitely save weight. On the whole, I'd have to say it's probably a wash.

        Love the car. Love the engine. Not sure I love the combination. Guess it would be OK if I could buy a Grand National with a twin-turbo 20B in it. ;-D
      • 7 Years Ago
      Are you crazy a LS in a RX7 that thing would be way too heavy, i rather have a high reving twin turbo rotary than a fat V8.

      And if you want more power than the RX7 has just drop the twin turbo 20B in from the JDM cosmo.
        • 7 Years Ago
        The misconception that the Rotary is a very light and superior engine is both funny and sad.

        Yeah, It is so good only one car company in one of their model uses it. Its all PR stuff, stop watching racing cartoons and drooling over import tuner pictures.

        I am sure Ferrari is planning on replacing their V8 in their F430 with a Rotory very soon.
        • 7 Years Ago
        First off, this isn't an LS swap, it's a V6 from a GN (illiterate much?).

        Second, an LS swap is -not- heavier than the rotary, it comes out with essentially the exact same weight distribution as stock, with a hell of a lot more power, and a hell of a lot better fuel economy and durability. The LS is the engine the RX7 wished it had from the start.
      • 7 Years Ago
      Tragic...they ruined a brilliant car.
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