Encyclopedia Hoonatica: DOHC Straight Sixes

By Peter Tanshanomi Mar 14, 2016

2004 Vortec 3500 5-Cylinder Inline Engine
‘Round these parts, we love straight sixes. But they can sometimes be regarded in America as outdated, low-tech beasts (except for BMW fanbois, of course). But the inline-six engine has progressed over the years into something as advanced and sophisticated as any other internal combustion configuration, including the use of dual overhead camshafts. In fact, DOHC inline engines have the advantage over vee engines in weight, cost and complexity, since the cam drive apparatus does not need to be duplicated for two separate heads.
So let us celebrate the DOHC straight six by compiling a comprehensive list of all the different iterations of this configuration.
The Caveats (there are always caveats):

  • We are listing engine designs, not cars. The number or variety of different vehicles an engine ended up in doesn’t matter.
  • Conversely, different generations count separately. If it’s got a new block or new head casting, it’s a new entry.
  • We’re looking for mass-produced, road-going engines. No grand prix works specials.
  • Diesel and petrol are both allowable.

Difficulty: Medium Hot (as long as you don’t bite into the jalapeño seeds).
How This Works: Read the comments first and don’t post duplicates! Bonus points for adding photos.
Image Source: counterman.com and Wikipedia.

By Peter Tanshanomi

Tanshanomi is Japanese [単車のみ] for "motorcycle(s) only." Though primarily tasked with creating two-wheel oriented content for Hooniverse, Pete is a lover of all sorts of motorized vehicles.

0 thoughts on “Encyclopedia Hoonatica: DOHC Straight Sixes”
  1. Older versions of the Cummins ISX15 had dual overhead cams – one to activate the valves, the other to activate the injectors.

      1. I know where there’s one in L.A. that is exactly that – and the owner decided to go with the V12.
        It’s quite an experience, and confuses the hell out of the Rod & Kustom crowd who haven’t seen it before.

    1. Let’s not get ahead of ourselves, as there were a heck of a lot of SOHC engines post 1978. From the M30 to the M20 and even the diesels, starting with the M21. Those are just the ones I’ve had personally, so I’d imagine there are more too.
      Now, post 1992 I could go along with.

      1. M30 and M20 were released before the M88. I guess I should have been more clear as I was looking at what year the engine was released and not necessarily the year range they were used. And I said “virtually” since the M102 and M106 were SOHC since they were derived from the M30. Also, I was only looking at the gas engines.

        1. True enough, counting initial release date the majority and excluding evolutionary updates (the M102/6 as you mentioned and the M21 as it’s M20 based) all BMW sixes, excluding the M51, since 1978 were DOHC. Just funny to think of it that way!

          1. I know what you mean. I was thinking late ’80s or early ’90s would be where they were committed to DOHC.

    1. I covet one of those lumps like you would not believe. I’d probably put it in a Maverick…or a Fairlane…or an early Cougar…

      1. Yeah later ones were twincam 24v beasties. Even before you go into the likes of Irmscher and the Lotus version…

      1. A better case to be made for calling it an offset-I6. Only as much vee as was required for packaging purposes. Well, that and to make your camshaft supplier twice as happy.

    1. This looks like a twin cam but it is not, it is not even overhead cam! BMW 328 engine (later used in the Bristol 400-406) with cam-in-block and two shafts of rockers to drive the valves, you can see the tubes for the pushrods from the inlet to the exhaust rockers in between the intakes.

  2. Volvo’s B6* engine, which was available in 2.5, 2.8, and 2.9L iterations, with and without turbos, with manuals and automatics, and mounted transversely and longitudinally with RWD, FWD, and AWD.
    To boot, it was the largest-displacement part of a modular engine family that included 4-cyl and 5-cyl. I’m not sure if it was true for the fewer-cylinder-count engines, but the 6-cyl head was co-developed with Porsche.

    1. I love my newer M series engine in my 84 supra, and the turbo variants in the mk3’s can be quite potent.

  3. BMW, as is their obfuscatory way these days, hides their best current motor in a 700+lbs motorcycle. It’s the 160HP 1600cc DOHC I6 from the K1600XX models. By the beard of Brünnhilde, why can’t they do anything fun, like a CBX-alike standard bike with this motor?

      1. Oh dear, those bars…Does anyone actually *ride* their motorcycles these days?
        “I was inspired mostly by mail slots and the Center position in football…”

    1. Don’t forget the M series was around long before the 5m, started in the 60’s, made it into the 2000gt, and went all the way to the mk3 turbo. It was like their small block chevy almost. I love my 5m-ge.

    1. OK, nothing new here; I think there’s already an image of one of these in the original post!

    1. SsangYong still offer two MB-derived petrol I6 in the Chairman: a 3.6l and a 3.2l. Trouble is, they’re wrapped in a Chairman…

    2. New straight sixes arriving in the next two years to replace all the current MB V6s. Tooling is being installed. Another modular engine of 3, 4, 5, & 6 cylinders in line.

      1. Here is a pretty mad video from one of these cars. I’m not sure what speed he gets out of shape at the second time, probably 100mph plus?
        I have had a ride in a 570 rwhp FPV F6 Typhoon, but it was on the highway so completely indistinguishable from a standard car!

        1. This is the real strength of these engines, 11.0 sec 1/4 after driving 1600km
          I think I see a mildly worked Territory Turbo in my future garage.

    1. It took me a second to realize that I was looking at the intake manifold. At first I was wondering why the exhaust goes into the transmission.

  4. Because we can never have enough mentions of it: Ford’s T-Drive engines were designed to be a family of 4, 6, or 8 cylinder in-line motors, all with twin overhead cams.
    The photo below of the 6-cylinder from the Thuderbird doesn’t really make that clear, unfortunately.

    1. Produced from 1924 – one of the first DOHC production engines (as distinguished from racing engines that existed from 1912)

  5. Bentley 6-cylinder from the 6.5L/Speed Six initially with a whopping 147 hp; mind you this was in 1926 with just 4.4:1 compression. The later Speed Six form had 180 hp at 3500 rpm. The engine was later stretched to 8 litres with a 4.3″ bore and 5.5″ stroke, for 220 hp.

      1. I can’t actually find a quoted torque figure. I don’t imagine it was that impressive by today’s standards, because again 4.4:1 CR.

          1. I did find a reference to the power put out by Jumbo Goddard’s twin-turbo 8-litre: 550 bhp! Still doesn’t sound impressive, but the rev counter only went up to 4000 rpm. I remember reading about the car, when they first put the turbos on (only two because there wasn’t room for three!), they kept blowing holes in the pistons and after putting a boost gauge on revealed it was running at something like 48 psi! Because the Bentley engine doesn’t have a detachable cylinder head the usual symptom of blowing the head gasket didn’t act as a warning sign.

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