Thread: 2 Litre Mods

Originally Posted by rover-56

The 2 litre engine responds surprisingly well to power modifications, it is a crossflow design which has been strangled in order to achieve low speed torque.
You can replace the inlet manifold and carb with a 4 branch design manifold fed by a 2 barrel progressive Weber carburettor, and replace the exhaust manifold with a similar 4 branch 2 into 1 header, and the result is amazing.

I bead blasted my 1600cc manifold last week and had a good look at it last night. The design of the branches is atrocious, with the centre branches having to change direction several times before the gas can reach the cylinder. There is also an incredibly small inlet hole just below the carburettor, which is as Terry described and restricts gas flow into the engine.

In contrast, the porting in the cylinder head is very good with no obvious narrowing, although I haven't tested it yet.

Out of interest Terry; what make of inlet manifold did you use and where did it come from? I would think a free-flowing inlet manifold, even with the same carburettor and exhaust manifold, would make a huge difference to performance.

Doesn't the coolant exit the head via the inlet manifold ..might be tricky if you want to try another inlet manifold...setting it up
Mike

Originally Posted by series1buff

Doesn't the coolant exit the head via the inlet manifold ..might be tricky if you want to try another inlet manifold...setting it up
Mike

Indeed it does!

I was thinking about it the other day; the water jacket on the manifold seems excessively large, compared to more modern cars that also employ this feature. Areas of Oz such as where I live, probably don't need the water-heating feature at all but in any case a new manifold could be designed with a different water jacket and branches. A cobber of mine who is a mechanic well-versed in cars of this vintage, suspects that the water-heated manifold was favoured in very cold climates running on the low-octane petrol of the 1950's. Or alternatively; it might be possible to have the water exit from the head into a casting which is then connected by hose to the short pipe at the thermostat housing. This would enable a pattern-maker to concentrate on a simpler pattern which is only concerned with gas flow.

I think I could make the manifold pattern but my knowledge of modern core-box making and core sands is non-existent, which hampers me completely

Any pattern-makers out there who can give me some advice?

Originally Posted by chazza

Indeed it does!

A cobber of mine who is a mechanic well-versed in cars of this vintage, suspects that the water-heated manifold was favoured in very cold climates running on the low-octane petrol of the 1950's.

yes that's true ... apparently there was also a fuel available called POWER KEROSENE ... older tractors used it . It was different to normal household kero..how I dont know . During WW2 some car owners fitted pre heating devices to the inlet manifold ..to heat up the kero as petrol was very hard to buy, legally anyway . Kero was illegal as a car fuel as there was no tax on it ..but some did try it . You would start on petrol....then change over to kero after the motor warmed up.

Originally Posted by series1buff

yes that's true ... apparently there was also a fuel available called POWER KEROSENE ... older tractors used it . It was different to normal household kero..how I dont know . During WW2 some car owners fitted pre heating devices to the inlet manifold ..to heat up the kero as petrol was very hard to buy, legally anyway . Kero was illegal as a car fuel as there was no tax on it ..but some did try it . You would start on petrol....then change over to kero after the motor warmed up.

Power kerosine was the normal fuel for most tractors until probably the late fifties when diesel started to take over. As stated, start and warm up on petrol, then change to kerosene. It has not much to do with lighting kerosene, being more volatile than that but less so than petrol (hence the need for a hot spot manifold. Most tractors using it were designed with an exhaust heated hot spot on the manifold, often running a lot hotter than is usual with petrol engines.

The reason that the Rover engine uses coolant to heat the manifold is that it is effectively a crossflow head, so the exhaust is on the other side, and it is easier to pipe water round than it is to pipe exhaust round. Similar manifold heating systems were used in contemporary Peugot and Citroen engines with crossflow heads. Modern crossflow engines with fuel injection can get away without it because the port injection makes icing almost impossible and inadequate vaporisation is dealt with when cold by the ecu adjusting mixture to compensate, and any unburnt fuel heats up the catalytic converter.

I would be careful about making the intake too free - while this will certainly increase the maximum power, it will also move it to higher rpm and make the power and torque peaks more pronounced, which while it may improve the maximum speed, will not improve the driveability.

John

Originally Posted by chazza

Indeed it does!

I was thinking about it the other day; the water jacket on the manifold seems excessively large, compared to more modern cars that also employ this feature. Areas of Oz such as where I live, probably don't need the water-heating feature at all but in any case a new manifold could be designed with a different water jacket and branches. A cobber of mine who is a mechanic well-versed in cars of this vintage, suspects that the water-heated manifold was favoured in very cold climates running on the low-octane petrol of the 1950's. Or alternatively; it might be possible to have the water exit from the head into a casting which is then connected by hose to the short pipe at the thermostat housing. This would enable a pattern-maker to concentrate on a simpler pattern which is only concerned with gas flow.

I think I could make the manifold pattern but my knowledge of modern core-box making and core sands is non-existent, which hampers me completely

Any pattern-makers out there who can give me some advice?

This may be possible. The thermostat housing on my 1600 must have corroded through, as the previous owner removed it and replaced it with a piece of plate and pipe. The engine runs well even though the water heating has been removed. This is probably because it does not get cold enough to need heating.

Aaron.

Ah, quite interesting!
On my car the back of the thermostat housing had corroded through leaving a nasty big hole for the water to flow through.

Thanks for the reply John. I know bugger all about torque and driveability compared to gas flow through the head. Looking at my collection of 2 1/4 litre manifolds, it appears that they are not nearly as restricted and the branches are more sensibly shaped compared to the S1 engines. Can you reccomend any reading on the subject? In the meantime I have researched modern moulding sands and have the germ of an idea for making a substitute. Incidentally, increasing the maximium speed doesn't interest me but making the thing more fuel efficient and a bit nippier at lower speeds does,

Cheers Charlie

Originally Posted by chazza

........
Thanks for the reply John. I know bugger all about torque and driveability compared to gas flow through the head. Looking at my collection of 2 1/4 litre manifolds, it appears that they are not nearly as restricted and the branches are more sensibly shaped compared to the S1 engines. Can you reccomend any reading on the subject? .....

Not really - my knowledge comes from reading lots of bit and pieces plus experience over the last forty-five years - the nearest thing to a reference I can think of is the only book I have on the subject - "The Modern High Speed Internal Combustion Engine", Ricardo & Clyde, 3rd Edn. 1941. At least this is probably the book that the designer of that engine used! It is difficult to compare the manifolds of the 2.25 and the 2.0 engines because the combustion chamber shape and the gas flow within the head are quite different.

When you improve the overall flow of gas into the engine, you enable more mixture to get into the engine, particularly at higher speeds, which will increase power at higher engine speeds, but make little difference at low engine speed, since there the resistance to flow is proportional to the square of the gas velocity. This has the effect of more power at higher rpm, but since there is no difference at low speed the power is more "peaky". A further problem is that unless the improved flow is very well thought out, the mixture to different cylinders may be different at all speeds, leading to rough running and reduced torque at low speeds. Not so much a problem with four cylinders, but particularly with sixes, the pulsing effect (think of tuned exhausts) can really cause problems for getting even mixture to each cylinder. This is where the advantage of multiple carburetters comes in, as well as allowing more mixture, it sidesteps the "getting it even" problem.

In the case of the 2.0 litre engine I suspect a well engineered two carburetter manifold might improve both maximum power and low down torque.

John