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German American Hot Rod Project!

Hot Rod BMW Z3 Project

If we haven’t had enough interesting discussion and varying opinions about what a proper performance car should be with the recent 1974 Mustang Cobra II V8 here on Barn Finds then this entry should provide additional food for thought. This one is a first for me and I’m a BMW fan who tries to keep up to date with performance developments in the brand. But this performance development is something the engineers back in Munich never thought to create: a tiny Z3 roadster with a honkin’ big V8 engine courtesy of Corvette via the recent Pontiac GTO. Find this hot rodded BMW Z3 here on eBay with the reserve not yet met and 4 days to go.

Hot Rod Z3 with an LS1

It’s the old hot rodder’s trick: stuff the biggest V8 you can find into a small, lightweight chassis – and then hold on! The fellow who came up with the idea of transplanting a 5.7 liter LS1 from a 2004 GTO must have had no reservations about how much power this little German roadster should have, 470 HP in this case. Mind you, this is a project even though it looks complete. The engine has been hot rodded beyond what Corvette and Pontiac did, and is already installed. It has an exhaust system and some professional reinforcements to the BMW’s subframe. That last part answered most of my questions about how the little roadster will handle the enormous torque that the LS1 puts out, but one question remains: will the stock diff be able to stand up to the power?

BMW Z3 Rear End

We don’t know the answer to that last question because the car does not appear to have been run – at least, not in anger. That’s because the car has an overheating problem that still needs to be corrected. That’s probably because the stock radiator is still in the car and likely doesn’t move enough of the heat produced by the LS1 into the air flowing through it. The car doesn’t seem to have a fan, at least between the rad and the engine. But assuming that problem can be solved, the question comes up: Does the vehicle as a whole work? Is this a proper modern version of the hot rodder’s dream of big engine small car? Or should we be going back to Deuces and T-Buckets, even if most new builds will have to make do with “Glass” bodies?


  1. don

    I always thought a Z-3 should have a 215 aluminum block buick in it. The corvette is a bit heavy but then hot rods are rarely well balanced.

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    • Rick

      The 215 aluminum Buick is pretty dated now. But I bought a MGA with a blown engine in 66 and put one in it. It would not run with the dudes putting 260/289 Fords in everything in a drag race but it did handle just as well as a stock MGA.

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  2. Randy Forbes

    It’s got at least one (>1) thing going for it; they used my trunkfloor/differential mount reinforcement package on the rear end!

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    • jim s

      more information on the package, please.

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      • Alan (Michigan)

        Search this: Randy Forbes dual ear rear subframe reinforcement kit.

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    • George Bauer

      Randy did my subframe on my 98 M Roadster. It kept the car from being totaled in an accident. Quality stuff!

      Couple things on this car and the write up: the radiator fans on the Zs are dual: clutch fan on the motor and electric in front of the radiator. Many people remove the clutch fan for a few ponies. I know a guy with a 1,000 hp M Coupe. I’m sure it has an aftermarket radiator so I know the cooling can be solved.

      The diff can be built to take power but this is likely an open diff. Get a used posi. Last I looked they’re under $500 if you shop.

      Looks like a good buy to me.

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  3. julian

    5.7 litres on a 1.8 litre radiator……………. could this be the first problem?
    not much ground clearance?
    Does it handle? – no of course it doesn’t , but its great away from the lights!!

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  4. Randy Forbes

    Actually, it was a 2.5 ltr (marketed as a 2.3, but that’s another story…) so it would’ve had the same radiator as all I-6s (up the 3.2 ltr ///M versions). There’re a few swapped LS-xs in these doing fine on the stock rads, so there are other issues to sort out. However, there are uprated radiators available from vendors such as Zionsville, and adding an engine oil cooler is rarely a bad idea.

    As for the weight and balance, those I-6s are no lightweights either (cast iron block on a lot__but not all__of them) and the V8 does sit further rearward, getting some of the weight OFF the front axle. They were slightly nose-heavy to begin with, so the V8 could easily prove to be MORE balanced, not less.


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  5. jim s

    car is to new to hotrod, how would it ever pass a smog test? BMW made very fast versons of the car already. i am missing the point of doing this and i think the seller is out of ideas/ time/money on how to solve all the problems/issues.

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    • OKCPhil

      Many of the central US states don’t have emission testing on any vehicles. In Oklahoma there are zero annual inspections so if you tag it you can drive it. I think MO is the same. Most of those annual inspections are just a scam anyway. Much too open to interpretation by the guy at the inspection station so rarely fair.

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  6. mtshootist1

    We don’t need no stinkin’ smog inspections in Montana..

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  7. MH

    Im in Minnesota. If it has tires you can drive it. No testing here. Chains are still allowed up north out in the back woods.

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    • johnforsman

      MH is right about emissions testing in MN. We had it, but less than 1% of vehicles failed. We have winter and road salt, does away with cars before emission failures.

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  8. Horse Radish

    I am very skeptical of these kinds of ‘conversions’.
    Especially,if the next owner gets to sort out unsolved problems !
    BMW made a V8 even V12.
    Not like BMW was known for having bad engines ?, no ?
    And if you want a GTO engine, why don’t you drive a GTO ?

    To each his own.
    Too much time effort and money wasted in my eyes.

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  9. Chris Member

    Wedging a V8 into a Z3 seems like a lot of effort for a questionable amount of return.
    My previous Z3M roadster did 0-60 in just over 5 secs out of the gate already.

    I don’t get the point either…

    (and I had Randy’s reinforcement package on mine to handle what the factory clearly forgot)

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  10. cory

    im gonna go with seemed like a good idea at the time but now I can’t get it to work. I respect the attitude, and really we need more guys like this. not enough backyard crusaders doing ridiculous stuff. I would really like to see it finished though.

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  11. Alan (Michigan)

    I know of one Miata with the same engine/trans swap. He used the diff from a CTS-V. What an impressive car!

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    • Horse Radish

      He can cut up a Miata for all I care

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  12. Dave

    Come on guys, it’s a modern version of a hot rod! It’s no different concept than Carroll Shelby jamming a 427 into the AC. When did car guys turn into such purists that we can no longer appreciate a fun idea with some actual effort behind it. Hot Rods are usually built so we end up with something no one else has, and because we wanted to build it that way. It’s not a collector or even a rare car so why not let your imagination and a spare LS engine be put to use. A Car like this with a cammed v8 would really turn heads.
    Whether it fits your particular idea of what a proper car should be is of no consequence to the builder and why we all watch to see what’s featured in the daily offerings from Barn Finds.
    I’m off my soap box now.

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  13. Vince Habel

    a bigger radiator and a couple of electric fans should cool it.

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  14. Achman

    E36 M3s with this swap or LSx swaps are pretty common.

    Shorter car+Z3 handling issues+power = fun or fright

    Flyin Miata has it down to a science with the Monster Miata.

    I would be putting my money towards their kit.

    Buy this Z3, take out engine, put in Miata, sell Z3 for parts.

    This coming from a 2 BMW owner…

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  15. gunningbar

    BMW salesman told me:
    Difference between a BMW and a porcupine?
    With a porcupine the pricks are on the outside.

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    • Horse Radish

      Priceless, and so true……for the majority.

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    • johnforsman

      The joke was more alliterate when it was the difference between a Porsche and a Porcupine, which was how I heard it in 1980.

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  16. Dennis M

    As others I do not get the point either. My ’98 2.8L Z3 is plenty quick, well balance and a joy to drive.

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