An Unlikely Race Engine – The Ford Flat Head V8

I have been playing with old flat head V8’s recently. Helping to coax a couple back into life at the Hokitika Industrial Heritage Park. That got me thinking of the V8 Specials that raced when I was young. I have in mind a “members cars” article on one of these, but that idea needs a bit more research. So as not to waste what I’ve got already this article sort of popped out instead.

The flat head Fords were a mainstay of hot rodding, speedway and track specials almost from the day that they first hit the roads in1932. Curious in a way, as a less presupposing race engine than the Ford flatie is hard to imagine. All the poor breathing of a side valve layout, plus a torturous exhaust port route right across the block plus built in overheating because of those water cooled exhaust passages.  Yet for all of their humble design quirks they were still cheap horsepower.

It didn’t take long for the engines to find their way onto the racetrack. The first private Indianapolis entries were made in 1934, and a works supported build of 10 cars was almost ready for 1935. In the event four of then made the field. A hurried build and development program put them all out for the same trivial reason, seizure of the steering box placed too close to the hot engine. These front drive Harry Miller built cars are a visual joy, and re-engined versions were fielded for the next 10-15 years. One of them even became the grandfather of the mighty Indy Novi’s. In 1941 the old V8 was whipped out of the chassis, (or more correctly the old Offy in this particular car as the Novi was its third engine), and voila the fastest but most ill handling car in the field. A chassis comfortable with the modest 150HP or so of side valve V8 was not up to the 350 plus of the first Novi engine. Never the less by putting a block of wood under the accelerator pedal so it couldn’t run at full throttle it finished 4th.) The Novi was a hemi V8 built specifically to better the power of the 8CL Maserati that had dominated the immediate pre-war Indy races. In the late ’40s the humble side valve Ford got a hemi of its own, but we will come to that later.

Like the “T” and the “A” before it a whole industry grew up around extracting more power from Henry’s pride and joy. (Google for a good run through on how to more or less double the factory horsepower). But there was a catch. The power available out of any engine is a function of how much air you can get through it. With any flat head the limiting factor is the torturous path of getting air into the cylinder. But in addition the Ford flatie has an even more torturous exhaust gas path. Running inside the water jacket from one side of he block to the other creates another limiting factor. The exhaust ports are effectively water cooled. The extra heat soak means the whole engine runs hot. More power means more heat, so hot rodded flaties are renowned water boilers.

If you are a Ford 10 fan you will be familiar with the side valve performance enhancement trick of the Inlet over Exhaust (IoE) conversion. (The yanks call this an F head). The inlet valve is taken out of the side chest and put in as an overhead valve. The exhaust valve and port are left where they are. The result is instant horsepower. Such a head on its own, with no other modifications will lift 100E engine power by about 35%. (Google “Vintage Automobile Racing Engines” to see a collection of conversion kit examples from way back). The IoE trick doesn’t work with the Ford flatie as retaining the original route of the exhaust ports also retains what caused the overheating problem in the first place.

So F heads on the flatie were done the other way around, in an Exhaust over Inlet configuration. This addressed the exhaust heat problem but left the original inlet tract in place. The end result was no significant power increase over a well hotted flatie, after all the inlet passage restriction still remains. 

The Iskerderian website notes that these F head conversions were developed to address the overheating problem on flatie equiped trucks. (A truck spends much of its time at high load factors). Never the less the hot-rodders saw the competition potential in the technique. The left hand picture shows a set of “Maxi” brand F heads on Vic Iskerderian’s first Hot Rod in 1938. Such a conversion still needed all of the normal side valve performance enhancement tricks to gain race engine power levels, but this time with a promise of greater reliability.

The hardware for such conversions became available very soon after the introduction of the flatie in 1932. The picture on the right is from the 1936 catalogue for Alexander Engineering. It  shows an F head as being just one of the special equipment options offered by that company. (Bespoke cylinder heads, cam grinds, F heads and a single overhead cam conversion all appear on their menu). Nor were they the only suppliers in this game. (Google Birner, Dixon, Riley, Smith Jiggler and Velocity to name just a few more).

Wilder overheating cures involved cutting the exhaust ports into the centre of the V and/or swaping the port functions so that the old inlets became the exhausts and vice versa. Now contemplate the inlet tract involved in all of that. A more subtle speedway tweak entailed reversing the engine rotation direction and using the drive torque reaction to best advantage on track that only ever turns left. 

But were these F heads really necessary? The May 1999 Classic Car Magazine includes an interview with the kiwi speedway midget legend, and long time flat head V8 user, Frank Brewer. He said that the overheating was so severe in a long race that reliability was compromised to the point where track owners would refuse entries to V8 60 powered cars. The problem was obvious, and just as obvious to Frank was the solution. Use an external water pump and slow the water circulation rate down, and add in a couple of manifolds to re-direct the water into the blocks between the cylinders. Take great care in the construction details of the radiator. Then take it out and gain three World Midget Championships against the Offy engined cars. (Note that the Midget rules were amended in the late 30’s to allow 140 CI side valve engines to compete against 100 CI overhead valve ones, even so the twin cam Offies still retained a power advantage).

The full cure is an overhead valve arrangement. The previously mentioned Alexander OHC conversion was such. But better known was the Arkus-Duntov brothers hemi head conversion kit. Again this was not intended as a race track modification, being originally developed under a factory contract as a fix for English Thames trucks. When used in London refuse collection service their overworked flaties were an under-powered over heating embarrassment. In the end Ford did not take up the Ardun but addressed the problem by using a bigger flatie.

It appears that the early Ardun conversion kits may have been made by Allards in England. True or not they quickly took them up for their sports cars. Alas valve train weight and gas flow problems not important in a humble truck, made them less than suitable for competition use in their original form. The project was taken over and the problems eventually cured by the American hot rodders.

Ardun type conversions involve blanking off the entire side valve chamber and using extended pushrods to operate a full set of overhead valves set in a hemispherical combustion chamber. Google “Stephens Denver” and “Emisul” for variations on the theme. The Chrysler hemi based “Emisul” conversion for Brazilian production Simca Vedettes was rated at an impressive130-140 hp, not at all bad for a V8 60 136 CI  (2.2 litre) based engine.

Staying in South America also gives us a fine example of the ultimate flatie conversion. In 1951 Alfredo Pian built up a one off twin overhead cam, three valve per cylinder conversion on a Mercury block, with enough horsepower to dominate the Argentine formula libra championships for the next few years. (Alfredo’s F1 career was cut off by an accident before it really began. Look him up, his is a fascinating story). The twin cam “Davis” conversion is also worth a look, as is the twin cam look alike “Adams Moller”. (A variation on the BMW/Bristol technique using the original low camshaft and cross head pushrods for the exhaust valves).  V8’s being V8’s and nostalgia being nostalgia most of these old modifications are back in production again. If you want to play the “retrospective special” game with this stuff the only thing you need is the cash to do it. Or take the easier route and use the engine that replaced the flatie in the eyes of the hot rodders. The Small block Chevy. Easier to find and still in period. Good luck.