Drysdale Godzilla V-Twin

Ian Drysdale's Godzilla V-Twin with master and link rods and longitudinal cam

Ian Drysdale's Godzilla V-Twin with master and link rods and longitudinal cam

Ian Drysdale keeps popping up whenever we talk about interesting engines, the Drysdale V8, the Carberry V-Twin, Russell Sutton's radial and a whole lot more, but as often happens, while digging around for information on another engine, I came across the Drysdale Godzilla V-Twin which I hadn't seen before. Ian must have some gene that prevents him from building anything ordinary because once you remove the covers of this V-Twin, you know there's some wizardry involved.

Master and link connecting rods for the Godzilla V-Twin, master and link connecting rods,modeled after the rods of the P&W 4360

Master and link connecting rods for the Godzilla V-Twin, master and link connecting rods,modeled after the rods of the P&W 4360

The cylinders of the 50 degree V-Twin are perfectly inline on a single pin crankshaft, something Ian wanted to achieve, but without the common knife and fork connecting rods that limit high rpm performance. He knew the big aircraft radials used a master and link configuration, so, being a true motorhead, he bought a Pratt and Whitney 4360 and shipped it to Australia. Gotta love that. Connecting rods in hand, he knew what he needed to do and designed a master and link rod arrangement for the V-Twin. Working with designer Tony Foale, they came up with a design to get the front and rear strokes and timing just right. Hurdle number one had been cleared.

Drysdale Godzilla V-Twin longitudinal cam with 25 degree conical lobes drivien by one pair of gears

Drysdale Godzilla V-Twin longitudinal cam with 25 degree conical lobes drivien by one pair of gears

Knowing any classic V-Twin should have pushrod valve actuation, he again went the unconventional route with an old design dating back to the 1930s and used in Mercedes GP cars and some old farm machinery, too, a longitudinal camshaft. A single cam with 25 degree conical lobes and driven by one pair of gears actuates the roller bearing hydraulic lifters that run in direct line with the cylinders, an interesting way to achieve parallel pushrods and quite a contrast to the three cam arrangement of the new Indian V-Twin. The result is far less gear noise and easier assembly and it just looks cool, too, a big plus for anyone who appreciates these things.

As any modern engine should, it has 4 valves per cylinder and a pair of gear driven balance shafts to create a very smooth running engine. Of course, Ian wasn't done yet. While the engine can be set up with normal aspiration and fuel injection, it was designed from the start to incorporate a supercharger in such a manner that it's almost unnoticeable. In the photo at the top, the little mechanism behind the rear cylinder that looks like a belt driven twin rotor supercharger, is exactly that! When all of the covers are on, you don't see it sitting out there like that, so think of the fun you could have. Good stuff.

The engine will be available in 3 displacements, 1398, 1602 and 1836cc. Though nothing is certain yet, Ian indicates he's talked with several parties about possible production, now wouldn't that be interesting?

When you look at all of the innovative features here, you have to think there's a bit of head slapping going on in some other design departments, with a lot of "Why didn't we think of that?" mumbling among the folks. Of course the simple answer is, "You're not Ian Drysdale." Geez, I like the way he thinks! I wonder where this will show up first.

Link: Drysdale Godzilla (pdf)
Link: Ian Drysdale homepage


  1. Dano says

    Simply beautiful!
    It’s always great to see how some answers have sitting right in front of us. Link rod on a master, conical cam, these are nice applications to a Vtwin. It helps make for reliability and simplicity of manufacture.
    The supercharger is amazing, a sleeping lion waiting to be poked in the ribs.
    Can’t wait to see a video of this gorgeous chunk of metal operating!

  2. Paul Crowe says

    What really caught my eye on this engine was the cam, parallel pushrods with a simple and elegant solution, of course the master and link rods are pretty sweet, too.

  3. scritch says

    That conrod assembly reminds me of the old “Twingle”, a 2-cylinder “single” sold by Sears, made by Puch.

    • Dave says

      Indian’s new motor seems like its off to a good start without looking like another HD

    • says

      Presumably the new Indian engine will not only live up to all modern noise and pollution regulations, but also be possible to build at a price so it can compete with H-D. Wonderful as the Drysdale big twin is, it is probably not contrained by the former factor, and certainly not by the latter.

  4. B50 Jim says

    Wow — It’s like a Top Fuel Hemi from the 60s in twin form. The cam is an elegant solution — amazing nobody has thought of it before now, and the link rod is a stroke of genius just waiting for someone to apply it. Just shows how entrenched the thinking can get at big corporations. Why not turn the cam sideways or use link rods? “We never did it, that’s why.” This engine will pound out serious horsepower and huge bags of torque. Sure would be nice to see it in production — I’m positive I wouldn’t be able to afford one, much less a bike to pt it in, but imagine a herd of bikes rolling down the highway with these engines thundering in the frames!

  5. says

    B50 Jim, the cam arrangement is not a new concept. I do have a question though. If those are roller lifters, it seems to me that a large portion of the roller would be skidding on the lobe, as the diameter change means different linear travel for all but the tiniest portion of the roller? Kind of makes them into slipper lifters that look like a roller?

  6. says

    Ah, just looked at the Godzilla pdf and they are not roller lifters, Paul. That works and in fact I’d expect the lifter rotation speed to be quite impressive.

  7. Ian Drysdale says

    Some clarifications……..

    We changed to roller lifters later in the development, the photo was taken when we still used plain lifters. Conical cams strain the brain a little, but there is no sideways skidding of the rollers, they “see” a flat surface.

    The longitudinal camshaft design was unashamedly lifted from an Australian stationary engine from the 1930’s called a “Howard Hoe” ( they made rotary hoes ), albeit with some updating. I always thought it was brilliant when I was a kid on the farm and took the oppurtunity to use it in the Godzilla – as far as I know, no other V-twin has ever used tyhis set-up.

    Thanks for the interest. IAN

    • Tanshanomi says


      Thanks for taking the time to comment. You are truly an exceptional design talent and an inspiring designer.

  8. Adrian van den Hoven says

    Does anyone remember the three cylinder Sportster built by an American whose name escapes me (Klotz??) and who offered it to H-D? It also used this arrangement for the vertical cylinder and because of it the engine was balanced. I believe that he or his widow actually did give it to H-D or something like that but that H-D simply shelved it… I can’t find the issue of Cycleworld or whatever magazine that featured it. Cheers, Adrian

  9. Russell B! says

    Oh man, I remember reading about the Fueling W-3 with great fascination. Pity it is lost, at this point, to lawyers and name-calling.

    The Drysdale Godzilla is what the H-D Sportster engine could have been, if H-D engineers had been able to innovate instead of refine. Would love to see Drysdale hook up with USHighlands for a street-tracker with this engine.

  10. Ian Drysdale says

    The terminology has changed…..they’re master / link rods these days….

    I corresponded with Jim regulalrly, his death was a great blow. His conrod design was effectively a 3 cylinder “radial” with a one piece master rod and a pressed ( or bolted ? ) up crank – as ( almost ) all radial aircraft engines do. One rare exception is the P&W 4360 – 28 clyinder / 4 row radial engine, it uses split conrods with a one piece crank – which became the inspiration for the Godzilla master / link / crank design.

    I was told that we would never get the stroke or TDC mark right on the “link” cylinder – radials just don’t worry about this – however – with Tony Foale’s help, we got both the stroke and TDC marks pretty well spot on. IAN

  11. Tin Man 2 says

    It looks very nice, very inovative, I do question the need for 4 valves per cylinder. When you have a Supercharger pushing the mixture 2 simple valves would do just fine, as in the Corvette engine. Maybe this Engine was designed to run naturally in some applications and Supercharged in other apps. Its all Good !!!

  12. Medicated Steve says

    Should I keep my Buell? This looks like it could be one hell of a transplant. Any idea of a redline rpm? Wow. So Cool!

  13. Medicated Steve says

    I WISH I understood this enough to make a one off engine. I need to hit the books. Hartley has and always will have it all wrong. It’s up to people like Ian to make awesome transplants. This leads me to a very important question, will this be offered as a direct transplant?

  14. Steve says

    Could the tapered lobe camshaft arrangement could provide variable lift if the camshaft lobes were moveable in an axial manner? I know the timing would stay fixed on a singke cmashaft though.
    Nice Job. Very Clever.

    • todd says

      I think it would automatically vary the timing as well – though symmetrically. You would need to provide more clearance when the lifter ran along the smallest portion of the cone so that the valve still closes as the base circle increases up the ramp.

      It boggles the mind without mocking it up.


      • todd says

        OK, I just modeled it up in solidworks. I see that the contact on a flat lifter oscillates from side to side and there is very little difference between where it rides on the small diameter and the large diameter. It’s similar to a windshield wiper path without much shift in angle.

        The roller lifter rotates back and forth within a narrow angle as the roller follows the rising and falling of the cam surface. When the roller is not parallel to the cam axis it no longer sees a flat cam surface and the wear point moves from end to end of the roller.



  15. says

    Ian, thanks for the clarification. I saw the roller lifter reference in the pdf but the photo showed traditional lifters so I assumed that there had been a misprint, as the photo is quite clear. At any rate, if you were to take the large diameter and small diameter of your cam lobe and averaged it, I reckon if you indexed the roller and counted, it’d rotate precicely the number of turns to cover that averaged distance (of course that’s if it had absolutely uniform contact, probably impossible). Just a mental exercise in geometry, matters not a whit if it all works. Oil is a wonderful thing. When you were using a plain follower, how rapid was the lifter rotation? Why did you change to rollers?
    Best regards,

  16. says

    Ian, you may be interested to know that on some radial engine magnetos the points cam was ground to account for the variation caused by a master and slaved rod system. Most didn’t bother, and it didn’t seem to matter a bit.

  17. Ian Drysdale says

    The plan was always to finally use roller lifters, we just started with plain lifters as we experienced warpage when the camshaft was case hardened for the roller lifters, which caused the gear to “run out”. The plain lifters didn’t rotate too quickly, we put a perspex cover on the timing side so we could watch them. I think the plain lifters are still feasible, just that the roller lifters are “sexier” – and the lobes can be narrower.

    BTW, in response to one post – we designed it with noise & emissions in mind – there are hidden smog pump ports in the heads and there are other features to dampen mechanical noise.

    Unfortunately it won’t be available any time soon, we are still in occasional discussions with manufacturers, but no concrete plans at this stage.


  18. Charley says

    Other that the supercharger, can anyone explain why they think this engine would “smoke” a H-D V-twin of the same displacement? I agree, you don’t see that rod arrangement very often and the cam shaft arrangement is rather unique. Neither however offer any real performance or reliability advantages.

    • says

      It seems that the supercharger would be the key factor in that.
      However, the 4-valve layout can have better normally-aspirated breathing potential at higher rpms, if this engine can reliably reach those higher rpms with the stroke lengths present in the larger versions.

      It would all depend on the individua enginel builds, and the bikes they are residing in.

      • todd says

        Tom, the 4-valve set up helps at all RPM. With the two smaller ports you get increased flow velocity at any given flow volume and the extra valve area will increase total volume. However, all the additional surface area impedes flow, more so at higher velocities (RPM), and all the additional valve train components increase resistance. There is the benefit of increased valve seat area (the proportion of seat to valve area increases as the valve diameter decreases) which helps keep the valves cooler. You also get more “swirl” from the added ports, promoting better combustion.


  19. says

    I wonder if cooling for the rear cylinder is going to be a problem?

    Or is there a lot of valve overlap to allow the blower time to scavenge the rear cylinder exhaust gases with fresh air before the intake cycle, which may help with cooling?

  20. Jack says

    with as much power coming out of this setup…..i would love to see it go into a suitable trike…..I love it…very amazing design

  21. Paulinator says

    This engine employs a brilliantly simplicated valve-train and unit construction. The supercharger is optional and there are no fake fins or redirected exhaust ports. The master/link rod mounted to a one-piece crank on shell bearings also saves production costs/complexities. I think that the Polaris VP’s are kicking each-other’s asses for not putting out feelers to Ian Drysdale before the inertia of their in-house(?) development efforts carried them downstream from H-D’s discharge pipe. If Indian released this engine their future would’ve been a lot less limited. A Scout could’ve been a “Ducati hunter” if it sported a supercharged, short-stroke “screamer” version of this pump. As it is, if I see another oversized headlight and skirted front fender I’m gonna puke. Japan has thoroughly claimed that look as their own.

    Ian, please give Polaris a call. They will drop what they’re doing and take it.

  22. paolo says

    just WOW
    this should have been the new polaris indian motor
    its utterly unique completely distinct from harleys
    pushrods are high tech (see gm) and the 4 valves and built in air assist
    amazing hope he finds a licensee for this its a jewel

  23. says

    Hi Todd,
    According to David Vizard, the 2-valve is superior to the 4-valve at lower rpms because of swirl in the 2-valve, and that there is no swirl in a 4-valve(they are all tumble), which is why the 2-valve layout works better down there.

    In fact, he went as far as inventing a 4-valve design which promoted swirl, called the “PolyQuad” design, just for the purpose of improving lower rpm results in 4-valve engines.

    In long stroke engines which are often rpm-limited by the piston speeds from the long strokes, 2-valve designs are still often the choice where low rpm torque/horsepower are important for the use on highways for cruising.

  24. Lee Samuelson says

    I found a Deluxe/Spacke (Spache sp?) engine whilst cataloguing motorcycles for accession into the Reynolds-Alberta Museum. It had the master/slave rod assembly.
    One of the entries into a previous Great American Race -did I get that right?- had a blog of his race preparations. He was preparing a Sears with a Spacke… which he’d converted to a more modern conrod assembly.
    Lee in Alberta where a blizzard is forecast tomorrow.

      • Lee Samuelson says

        Interesting as all political organizations go. I was the second registrar. The collection was initially endowed by donations from Stan Reynolds. The Deluxe/Spacke engine was laying on its side on top of an oil drum. My drool piece was a Frayer-Miller air cooled 6 from way back when. Alas a pile of pieces.
        Melting has come, hooray,
        Lee in Alberta

  25. jurneyman says

    In reference to the 4-valve head design I agree with Todd. The air/fuel mixture atomization is more complete due to the higher velocity smaller ports, allowing for a more efficient burn due to the center-fire shallow combustion chamber. As far as low speed power or torque is concerned, a 4-valve head motor using the proper cam timing and rod to stroke ratio for its application has a greater torque range then any two-valve. The stroke will not affect the piston speed limiting the RPM and Horse Power if the proper rod to stroke ratio is used.

    • says

      Yes, well David Vizard does give seminars at various regional locations around the country, regarding engine technology.
      Perhaps you could attend one and have a chat with him about it.

  26. David Duarte says

    beautiful. Now someone just needs to build a motorcycle (and not a cruiser or chopper) around it that doesn’t hide it away under a ton of plastic.

  27. todd says

    Now I remember where I saw this cam setup before, Sears sold a V-twin bike in the ’20s or something with the same type of cam. Maybe I”ll see if I can look it up.


  28. says

    Ian: Congratulations on the new motor, and for your personal commitment to innovation in Australia. The new motor would look right at home in a full-volume production Convict Motorcycle!

  29. Alan Bray says

    Here’s a thought…imagine Indians new engine and its derivitives comprising 90%of Indian’s product line-up with one or two exclusive top-tier models possessing Drysdale V-twins? Polaris Industries obtains a truely desireably unique branding of “Indian”, Drysdale V-Twins kick down the commercial viability door and we participate in a new era of V-twin arguements and, dare I say, competition?

  30. says

    The problem as I see it is. People make these massive engines producing huge power. But the problem is where do you put the huge airbox and huge exhaust that you must have to go with it. In todays world you can no longer have straight though exhaust pipes. The American chopper market is dead forever because the next round of legislation won’t allow it. It you intend selling them you must comply with noise limits. In order to do that you’ll need a massive airbox and exhaust system, and as I see it, you’ve got no place to put it. An engine that size would require an airbox the size of a gas tank, and the exhaust the size of the two Buell mufflers. Twice as fugly.

  31. scat says

    And, the Indian even has a belt, to drive all THREE camshafts….this design has it all over the Indian wiz-kids.

  32. ryan says

    Will this design allow removal of the rods from the crank without splitting the engine, either pull through the top or drop through a pan of some sort?