The Opel Diplomat 5.4 Coupé

By Brendan Moore


1965 Opel Diplomat 5.4 Coupe

I was reading a piece in a European classic car magazine from 2005 (I know, a little late) that featured the Opel Diplomat 5.4, a car completely unknown here in the States, but one of my long-time favorites.

The article was mostly a road test against some other “super-coupes” of the era, and so was short on many of the details that I like most about the Diplomat 5.4 Coupé. Fortunately, since I am a bit obsessive about things like this, I can provide those details.

The first Opel Diplomat V8 Coupé rolled off the assembly line of body maker Karmann in Osnabrück, Germany in the summer of 1965. The top Opel was virtually handmade by the workers at Karmann. Since only 347 of the 5.4 Coupes were ever made, this handmade status would not be a problem in terms of satisifying demand, but it did conspire to drive the high price even higher. The price was approximately 25,000 DM, which at that time would buy you seven Volkswagen Beetles, nicely equipped. The car cost Mercedes-Benz money, but without the Mercedes star and this was a tough sell in Europe. The American-style looks and size (almost 200 inches) were both loved and reviled on the Continent. The car was not a sales success for Opel.

The Opel Diplomat V8 Coupé was the absolute zenith of the Diplomat range and came with a 5.4-liter V8 engine –advertised as the same engine that was used in the Chevrolet Corvette at the time and paired with the GM two-speed automatic transmission, the 230hp V8 engine pushed the Coupé from zero to 100 in under 10 seconds. That was incredibly fast for the era, and gave the Diplomat 5.4 owner bragging rights everywhere he went in Europe. Maximum speed was 206 km/h (125 mph), which was a pretty good top end for a two-speed transmission.

And the interior? I’ll let Opel itself tell you what the interior was like – this is from the company’s press release noting the 40th anniversary of the Opel Diplomat Coupe in 2005: “The top-of-the-line model was characterized by restrained luxury and elegance. The two-door vehicle was equipped with hydraulic steering and braking boost, disk brakes and fog lamps. The interior was dominated by thick carpets, opulent upholstery, real-wood inserts as well as a band speedometer going up to 250 km/h. Power windows, power exterior mirrors and rear foot-well lamps are among the exclusive details the great mass of drivers in Europe would have to wait for quite some time yet.”

Now, here’s something about the Opel Diplomat V8 Coupé that even the few people that know pretty much everything about the cars usually don’t know. Every article written about the car states that the 5.4 liter V8 (known as a 327 small-block V8 here in the U.S.) in the Opel Diplomat is the engine from the then-contemporary Corvette. Owners of the car will tell you the same thing. Even Opel itself makes that statement. Until recently, I too thought this was the case.

An auto enthusiast magazine here on this continent had a retrospective of the Chevrolet small-block V8 in one of it’s past issues from a few years ago (hey, I’ve been busy, OK?), and one of the interesting anecdotes regarding the fabled engine is from the interview with Bob Lutz, currently Vice-Chairman of GM worldwide, and formerly Head of Sales at Opel over 40 years ago when the Diplomat 5.4 was developed. In the interview, he happens to mention the Diplomat 5.4 Coupé and its use of the famous small-block.

Apparently, the small-blocks used in the Opel Diplomat 5.4 are special “endurance racing” versions of the standard Chevrolet small-block engine owing to the fact that the guys at Opel kept burning up the various small-block powerplants (including the standard Corvette engine) sent to them by Chevrolet during the sustained high-speed testing they did for the Diplomat. In order to replicate Autobahn conditions, they ran the cars at a sustained speed of 125 mph for hours on end, and in the process, destroyed quite a few engines. The Opel engineers first went through the stock Chevrolet 5.4 small-block engine, then a special “enhanced” engine that had some Corvette pieces, then the actual Corvette engine, and then were finally sent the “endurance racing” engines which made the grade and thus became the only V8 offered in the Diplomat 5.4 model.

So that’s the engine you got if you had an Opel Diplomat 5.4, and this may also explain why, that although not many Opel Diplomat 5.4 models were produced, you see a fair percentage of the few cars left with very high mileage and still running strong. The Opel Diplomat sort of had a Corvette engine, but not the production engines used in road-going Corvettes – it had the engines used in the Corvettes (and other cars) that did hard-core endurance racing like at Sebring and LeMans. It was a tougher, more durable, higher-revving (and more expensive) small-block V8 than the production Corvette engine, and a better engine all around.

It is unknown how many of the 347 Diplomat Coupes built between 1965 and the end of 1967 survive. One of the remaining ones is in the Opel Museum in Germany. It is a shame it is not driven anymore, but it is there to serve as testament to the grand experiment that Opel launched in 1965.

Many thanks to Karin Loeffler and Klaus Kukwa working on behalf of Adam Opel GmbH, PR, Germany for the photos provided. All rights to photos belong to Opel GmbH and cannot be copied, reproduced, or used in any fashion without express permission of Opel GmbH.

COPYRIGHT Autosavant – All Rights Reserved

Author: Brendan Moore

Brendan Moore is a Principal Consultant with Cedar Point Consulting , a management consulting practice based in the Washington, DC area. He also manages Autosavant Consulting, a separate practice within Cedar Point Consulting. where he advises businesses connected to the auto industry. Cedar Point Consulting can be found at

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  1. I lived in Germany in the early Seventies and as a young boy, my friends and I used to walk several blocks out of our way on our way home in order to walk by one of these cars. Just to look at it. Seeing that fender emblem photo brought back a rush of childhood recollections. Thanks.

  2. Wow – I’d never heard of these before. Such a cool-looking car, with its lines reminiscent of the Impala and Chevelle of its era, yet even cleaner. Neat story about the engine, too. It seems that an extra gear in the transmission would have made it easier to keep the engine in one piece while sustaining Autobahn speeds.

  3. Opel tried to sell a more expensive car than ususal in the late 1960s and the early 1970s, but it was not immediately successful, and they did not keep trying. So, back to the cars for the masses.

  4. Hi,

    I just had to move my Diplomat B 1970 to aother storage…as you can see it’s quite dusty…
    I acquired it way back in 1984 and ran it regularly into the 90ties…then i stored it in dry storage.
    One of the coming years i hope to fully restore it but i’ve been too busy with work, bought a house end 2005 and now getting married june 30th.
    You can find some pics of it at



  5. I just found this article through Google search – what a great article and what great photos! These photos are wonderful!

  6. Hi And thanks for a nice article!
    I am a proud owner of the 163th Coupe. I bought it in 1978. I’ve been driving ower 200.000 km since then -my Opel friends call me World Champion Diplomat Coupe Driver!
    Now about the engine, It is NO Corvette engine! Actually it comes from Chevy Nova. Nova had the first Chevy v8 engine equipped with Spinon oil filter, already in 1964.(others got it around 1968)The oil filter is mounted 13 mm/0.5inch up from oilpan. But the rest might be true about the special engine.It has for example a special oilpump and oilpickup with
    an attachment that normal Corvette engines got in 1995!
    The rear axle has the comforting 2:73 gear ratio. Engine revs 2200 rpm at 100 km/h.

  7. Great article, great car. I wonder what one of these cars is worth on the collector car market these days?

    Those European drivers must have been freaking out when they saw this car coming up on them on the Autobahn!

  8. Nova engine? Give me a break! This is no more a Nova engine than it was an engine that any other Chevrolet had that had a V8 engine in it.

    I researched this heavily and the author is correct. The engines used in this Opel Diplomat were the same enduarance racing V8 engines used in the Corvettes at Sebring.

  9. I never saw this car before and I am a big GM fan. Thanks for the information.

  10. These pics are awsum. Best quality pics I’ve seen of this car, ever.

  11. Great article! lots of insight and info. i almost bought one of these back in sweden in 1980. i grew up in the backseats of dad’s opels in the sixties and seventies. my dad is a devoted opel driver since the early sixties and presently drives an -04 astra. i remember that on one -61 opel rekord that he owned he had to buy a separate FM-unit for the radio in order to receive fm. it had tubes in it and we kids were fascinated by these glowing tubes that had to warm up and gave us sound. one guy i worked for in stockholm used to work at the gm dealer in stockholm and remembers doing a pre delivery inspection on one diplomat coupe they sold back in the sixties. these are truly unique cars that get very little attention. cars were more fun then…. Thank You! /magnus j.

  12. This can’t be any more cool, I wish I had one of these in my garage, I bet I would win every clascic car show I entered it in where I live.

  13. Just came across this article. The Diplomat Coupe had the 4.6 V8, not the 5.4 The 5.4 engines were used in the “B-Series” starting 1969 through 1977, but there was no coupe. I have had several Opel Diplomat and Admiral of the B-Series and was active in the Opel “K-A-D” scene (Kapitan, Admiral, Diplomat) back in the day.

  14. Great cars. I’ve had a sedan Diplomat A earlier.
    Hoping to get hold of a Coupe. Anyone who have one for sale??

  15. No, the author is correct about the engines in the Coupe!

    The standard range (sedans) of the Diplomat A are equiped with the 4.6 L. engine, but the Coupe where all built with the 5.4 L that came in the later B models!

    Beside, the Kapitän & Admiral A could also be ordered (special order) with the 4.6 L engine.

    Production numbers are:

    KAP. A V8 (4.6) 113 cars made
    ADM. A V8 (4.6) 622 cars made
    DIPL. COUPE (5.4) 304 cars made

  16. Its even so that a few 4-door sedans also had the 327″ (5,4 l) engine!

  17. Hi guys i own a 4 door diplomat 5.4 1971 and i would like to sell it. Cell phone 07956915580, many thanks.

  18. Great photos, but I guess they would be if they’re coming from Opel. I have been looking for information on this car, and thank you for this article, because it has a lot of facts and some very nice photos. Very nice work, kudos to the author! This is one of my dream cars and I am looking for in daily driver condition in Europe so I can bring it back to the States.

  19. Hi i will like to buy it, if you still have it.

  20. @Adam – did you read the same article I did? I don’t see anyone who owns one of these, and certainly the author does not.

  21. What a great post! I had no idea Opel ever made something like this!

  22. Well-written, thanks.

  23. Nice looking car. I’m not from Germany, so I’ve never seen an Opel, other than the Kadett or the 1969-72 GT. It’s a shame that neither the Kapitan, the Admiral, nor the Diplomat were ever offered here in the U.S.A. It would’ve been interesting to see what Opel could offer other than compact cars.

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