Installation of the French Flathead V8


You might have heard of these so-called French flathead engines that keep popping up and wonder what they actually are and how to install them in a Ford car. They are generally claimed to be "almost" identical to the US made Ford engines, but what is it really all about and what exactly to do. I have been so fortunate to get hold of one of these amazing machines as well as following the developments of other Ford owners installing them too in their cars. First a bit of history:

The Ford Motor Company has branches in many countries with distinct product lines and in the past that also included France. Here they merged with the French company Mathis under the name Matford and one of their later models became the Matford Vedette with the 60 hp Ford Flathead V8. In the beginning of the fifties Simca bought it all, so an almost identical Simca Vedette came the following year. It's an odd end that Simca made the Vedette for several years, and the very last of them were made in Brazil in the early seventies after Chrysler had taken over Simca. So the last of these legendary Ford flathead V8 engines for civilian use were made by the rival Chrysler in Brazil!

The larger 3.9 l Ford and 4.2 l Mercury engines (3.75" and 4" strokes with 85 to 125 hp) were also made in France for military applications and these engines are the ones that have become available after the French army stopped using them and sold out in the late nineties. The engines have presumably had multiple applications, but they have for sure been used in a four wheel drive heavy duty truck with the name SUMB (Simca Unic Marmon Bocquet). Some of these have ended up in a company in England, RR Motor Services, Ltd where they can be acquired for a fair price .

The French engines have come in several different setups but the block in all of them is almost identical to the Ford 8BA made from 1949 through 1953 except for the bell housing that is identical to the early 1932 through 1948 engines. As a consequence the engine can only be installed in the early cars, since it has half of the bell housing on the engine whereas the later has it all on the transmission. It is said the French engines are of a better quality (military specifications?), but generally they are compatible with Ford parts.

I will try to outline the necessary modifications and changes when installing the French flathead in an otherwise unmodified Ford V8 vehicle.

· The carburetor is a fine Zenith NDIX32 which has been used in cars like Porsche 356, Renault, FIAT, BMW V8 and DKW SP1000. Just like the Ford Holley and Solex carburetors the throttle body is made of cast iron and is hold onto the carburetor body with four screws. All of them have some kind of governor which should be removed or at least deactivated. The easiest way to do this is to find the throttle body from a standard version of the carburetor, because the entire governor is located here. It would also give some more power since the governor throttle body is only 2x30 mm and the throttles can only open about half due to the governor mechanics (!) while the rest of the carburetor and the intake manifold as well as the Ford Holley carburetors are 2x32 mm. A 2 mm difference might not sound like a lot, but for the cross section area that really counts, it is a difference of 14%. The half opened throttle and the turbulence around the edges will certainly also make a difference too. The DKW version has no acceleration pump, so in this case the arm and push rod from the military version will have to be adapted. Funny enough the Porsche version has no choke. The choke is of the by-pass type, and you will need a little ingenuity to get that adapted to the original pull-rod. The Zenith carburetor has four bolt holes like the Mercury teapot and although the bolt pattern is exactly the same, the teapot is 2x34 mm and the two channels also being closer together and will thus not match the intake manifolds 2x32 mm. Remember that the float chamber should be towards the front of the car. Another very important detail before the new throttle body is installed is the number of small channels in it. The original Ford distributor and the one on the French engine do only have vacuum advance and the take off for that on the carburetor should be the mean pressure between the manifold and venturi pressure. Therefore it is very important that there is a connection from the throttle body to the channel to the venturi in the upper part. As an example this is not the case in the DKW version, since it has a combined vacuum and centrifugal advance. If this hole isn't present, just compare the governed with the one you are about to replace it with, then the engine would run with way too advanced at lower loads and too little at full with lower performance a poorer mileage as a result. Just carefully compare the two and if needed drill the missing hole from the top into the vacuum take off channel.

· The small standard air cleaner fits the Zenith carburetor. Unfortunately this carburetor has a relatively flat top, so the Ford oil bath air cleaners of the hat type do not fit. So if a better cleaner than the standard is desired it will either have to be an oil bath cleaner of the type that mounts on the head studs or firewall or a modern third party like K&N.

· In general the engine is like Ford designed it including the various threads in UNC and UNF dimensions. The few things that have been changed by the French engineers are generally metric. E.g. the studs for the exhaust manifold are 7/16" UNC in the block end like the Ford blocks but 10 mm fine thread in the other end. They are otherwise OK, so unless you need to replace them to fit your manifold or header, just leave them in place since they are hard to get out. The Zenith carburetor is also metric, but the threads do not have a standard pitch, so don't loose them.

· To my knowledge there are two different types of oil pans: A very nice one in cast aluminum that will do right away and another one that has the bulk in the front instead of in the rear end. The latter cannot be used and it will have to be replaced with one from a Ford. The only modification to the oil pan is to move the oil dip stick from the rear to the normal location and fortunately there is already a brace in the casting for that. So just drill and cut a thread (1/2" UNF). New oil dip sticks and tubes are available but the length of the stick has to be adjusted to get the right amount of oil. The left by hole can be used for the return pipe when re-routing the oil filter.

· The water pumps have wide pulleys and look like the Ford truck pumps, but since they besides being water pumps also serve as engine mounts; something has to be done as they have been adapted for their military application and do not fit. A common practice seems to be to cut the excess off and bolt on a strong bracket. However this is not worth the efforts. The inside of the pumps is completely different from the Ford pumps, so when, and not if, they start to leak, there is no way to get a repair kit for them. Fortunately, the pumps from the 1949 through 1952 Ford trucks fit the block as well as the frame, and these pumps are readily available as used, repair kits, exchange or as brand new improved types. Unfortunately they are longer so there is no room for the fan in 1935 and 1936 Fords. The fan can barely be squeezed in with the French pumps. Later models should have plenty of room.

· There are no thermostats on the engine and to get that either use thermostats and thermostat housings from 1949 through 1953 Fords or get a small groove machined in the French ones to leave room for Ford thermostats. You will need to find some appropriate hoses for your car and e.g. Roulund Roniflex have a large variety of flexible hoses even with different diameters in either end.

· The distributor is French and it would be very hard to find replacements for wear and tear parts like points, caps, vacuum advance etc. Mallory makes new distributors but they are very expensive, so a standard Ford distributor is a good alternative. They can be found on eBay for a few dollars and up depending on their condition. The overwhelming advantage of the Ford distributors is that you can get any parts for them and you can even make them electronic with easy to fit Pertronix kits (12 V negative ground only). The engine front cover that holds the distributor is not exactly the same. The hole the distributor shaft sits into is 8 mm (5/16") longer and the distributor is fastened with a bolt on the shaft. On the Ford engine the distributor is hold in place with a bolt and clamp on the cylinder head. So either the shaft has to be machined to get it far enough in or alternatively use the front cover from a Ford engine and make the threaded hole for the holding bolt and clamp.

· The engines come with a big 24 volt 50 amp generator of the brand Paris-Rhone and a corresponding 24 volt starter. The starter is besides the voltage identical to the Ford starter. So at this point is has to be decided which voltage you want: 24 volt, 12 volt or 6 volt. In case of 6 volt just take the 6 volt starter from the engine being replaced (take the bendix drive from the French. If nothing else it is new and it fits!), and then in some way get or make an appropriate bracket for the 6 volt generator from the replaced engine. 24 volt is obvious with regard to the engine but somewhat problematic with the rest of the car, so I will not recommend that. 12 volt, negative ground is a good choice. All light bulbs are available as 12 volt, the battery, of course, but keep in mind that it is negative ground. The car was born 6 volt positive ground. The instruments should have a 12 to 6 volt voltage reducer so they don't break. The 24 volt generator can very easily be converted to 12 volt by connecting the field coils in parallel instead of in series. A voltage regulator from an air-cooled 12 volt Volkswagen with generator (got alternator in 1974) can be used, but the field coils must be connected correctly. The original 6 volt starter will handle 12 volt and unlike the 6 volt grinding start the engine will start promptly. However, in case of problems do never use the starter on 12 volt for prolonged periods.

· As mentioned with the fan, it is a tight fit - indeed in the earlier models. Since it has wide belts and thus pulleys it will not in 1933 and 1934 frames as the front cross member in these models is in front of the engine unless you make a dent in it. From 1935 onwards the cross member the cross member is behind the pulley and then just fit in. However, you must keep an eye on the distance between the spring clamps and the oil pan as you don't want them to touch. The French engine has stronger and larger main bearing clamps and the oil pan is therefore deeper in the front end. Consequently the engine should be raised a little (about ½") by putting some thick washers between the engine mount. Then the bolts might become too short and longer ones needed. There might also be problem in the rear end with an additional blinded brace (for magnetic ignition and some types of governor), and here you have to remove as much material as you dare and make a dent in the firewall for the rest. The braces for the engine to frame pull rods are not drilled up. They have to be drilled with great care as there is not much material here.

· They come with the same bypass oil filter as the later Ford engines but the pipes are run in a way that will at least not fit in the earlier models. It can either straight away be blocked off and removed or new pipes have to be made. The threads are standard US pipe thread in block and filter and the pipe ¼" thin wall cupper pipe which are available in any hardware store. The return pipe can conveniently be re-routed to the hole left behind by the French oil dip stick.

· The crank case ventilation pipe on the French engine would normally have to be modified too to fit. One way to do it is to cut it off at the rear end of the block and pop on a rubber hose that runs underneath the car. Another solution is to weld or solder on a pipe stud and install a PCV valve from a later Ford V8 engine of approx. the same displacement and run that to the intake manifold. On the intake manifold just below the carburetor there is a big hole with 20 mm thread where it can be connected. 20 mm thread is standard in hydraulics (at least in Europe), so it is possible to obtain a hose fitting to fit the PCV valve.

· It has the big 11" truck clutch and it should be taken out and cleaned before installation. Some engines are sprayed with protective wax including the clutch while it in others might have seized. Bear in mind that unlike the small 9" clutches the oil pan has to be removed to get it out.

· After all these efforts it ought to be painted in the correct colors. The oil pan should be black like the generator, starter and air cleaner. The engine is green up until 1941 and then it is blue. The intake manifold should not be painted and the military color is not easy to get off. Most of it can be removed with a paint stripper, but the surface stays green, so the last bit has to be sanded and polished away.

It might seem a little overwhelming but should on the other hand be reasonably detailed. And the reward for all these efforts is a brand NEW engine with more power and a heart of gold.

If you have any comments or additions to this please drop me a line at: so the list can be kept as accurate and complete as possible.

Good luck!


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