While there are many factors that contribute to a vehicle's overall weight, one thing I'm concerned about is the weight of an engine. Does a larger engine mean it's always heavier, or do the number of cylinders count as well? Just to be clear on what I'm trying to say, I'll give an example.

Engine 1:

Size = 7.0 liters

Cylinders = 8

Engine 2:

Size = 6.0 liters

Cylinders = 12

With all other factors being equal, is it possible to determine which engine would be heavier?

  • $\begingroup$ big things do tend to be heavier. What do you mean by "engine size?" $\endgroup$
    – Tiger Guy
    Commented Sep 25, 2021 at 3:15
  • $\begingroup$ For a given material, more volume of that material = more weight. Your question seems to not be worded to indicate what it really is that you want to know. $\endgroup$
    – DKNguyen
    Commented Sep 25, 2021 at 3:56
  • $\begingroup$ engine "size", for rough comparison purposes when shopping for vehicles, I think most often refers to total cylinder displacement. Even from same structure material, because of different pressures with diesel/petrol plus with possible compression, the power output -> required strength -> structural needs -> mass all vary $\endgroup$
    – Pete W
    Commented Sep 25, 2021 at 13:46
  • $\begingroup$ Please beware that weight depend on a lot of design choices and that weight might be or not be a design requirement. Being everything equal, an stationary engine is going to be a lot heavier than a motorbike engine - but probably also a lot simpler, sturdier and maybe cheaper. $\endgroup$
    – Pere
    Commented Sep 26, 2021 at 17:59

2 Answers 2


It is one of several factors that affect weight of an engine. The material of construction, the number of cylinders, type of engine ( overhead cams(s), flathead, etc, (ignoring radial etc)), gasoline or diesel, age ( cast iron engines from the 30s' weighed twice as much as modern thin cast iron of the same displacement), 2 cycle or 4 cycle, construction details (some have sheet metal sumps - some have thicker cast sumps). What do you want the answer to be?

  • $\begingroup$ +1 What do you want the answer to be. All else being equal scenarios depend on what falls into the all else. $\endgroup$
    – Abel
    Commented Sep 25, 2021 at 17:00

The main thing that comes to an mind is the material that the engine is made from.

Originally the engine blocks were made by of iron, however in recent years they've switched to aluminium.

More cylinders would mean more weight for the same stroke but I guess the total engine displacement would be a better in indicator.


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