Seven Engine Weight

[Nate M]

Does anyone know what the weight for the Austin Seven Sidevalve engine is both with and without the gearbox/ancillaries?

Additionally are there any significant weight differences between the Seven Sidevalve and later Reliant SIdevalve engines?

Though probably unlikely also interested to know if any weight figures exist for other Seven-derived engines from BMW, American Austin/Bantam and the Datsun SIdevalve?

[David Cochrane]

I don't know what the actual weight is, but they seem to have got heavier over the years...

[Colin Morgan]

From the Forum in 2012, where an American was pictured balancing one on his finger, or similar, which prompted the question of weight:

Ruairidh Dunford replied:  'Nearest engine I have to hand like the one shown, is three bearing with dynamo and starter removed. Sump and gearbox full of oil, it weighs just under 80kg, which is about 176lbs'

[Nate M]

From the Forum in 2012, where an American was pictured balancing one on his finger, or similar, which prompted the question of weight:

Ruairidh Dunford replied:  'Nearest engine I have to hand like the one shown, is three bearing with dynamo and starter removed. Sump and gearbox full of oil, it weighs just under 80kg, which is about 176lbs'

I see. Putting it in perspective, have read people claiming the later unrelated all-alloy Reliant weighed 58kg (some even going as far as to claim it being as low as 37kg if not including the gearbox) with the first non-alloy Reliant OHV engine as produced in 1959 (and claimed to be a downsized reverse-engineered Standard-Triumph SC engine from the 803cc Standard Eight that also ceased production in 1959) being said to have weighed half-a-hundredweight (or about 25kg) more than the old Reliant Sidevalve engine.

Meanwhile the much later Issigonis 9X engine that was said to have drawn inspiration from the Seven engine (at least in terms of compactness and construction) weighed about 200lbs or 90.7kg.

[A G Wood]

That's a good weight for the 9X, given that the current Ford Fox engine  [3 cyls/999cc/100-125 HP, cast iron block/alloy head] weighs in at 97kg.

[Nate M]

It is a good weight for the 9X in spite of its flawed and unviable design, which was out of step with what rivals were developing.

It is also makes for an interesting comparison with other small engines:

9X = 90.7kg
Reliant OHV = 58kg (also as high as 62.5kg and as low as 37kg minus gearbox - add about 25.4kg for non-alloy prototype version circa 1959 compared to Reliant SV for around 96kg)
Imp = 79kg
A-Series = 120kg (others claim lows as 112kg to as high as 147kg if including ancillaries)
Standard-Triumph SC = 125kg (also as high as 136kg depending on iteration others claim weight as low as 100kg - the 125kg figure being for late 1300 engine)
Fiat 100 Series = 100kg
Austin Seven = under 80kg (looking further it seems the Reliant SV's weight was about 71.6kg)