Hemis (I've seen the FAQ)

On the FAQ it says “There are no plans to implement these head designs. The reasoning here is that they were technically surpassed by other existing designs at the time the game starts in 1946.” under “Hemis, sidevalve, and flathead engines” Hemispherical combustion chambers are common on modern day cars and I see no reason why they would not be advanced enough. Hemispherical combustion chambers were high-end tech up to the mid-70s. Am I reading this wrong? Is it harder to implement than I am imagining?

Modern cars don’t use hemis, despite the name. Also including hemis would be weird without including other options of chamber design. All this I guess falls under “too minor effect on gameplay with too much research needed”.

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Hemis are already in the game. They’re just pushrods with extra quality.

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Hemispherical combustion chambers are standard on most modern engine designs.

As to the OP: Hemi in regards to OHV, is just as simple as +1 quality, the reason the famous Hemis made power was mostly due to very high compression, an aggressive cam, and solid flat tappet lifters with heavy springs. Something they have added to the current game.

The major design improvements were more from the canted valves and straighter passages.

Again, something easy to replicate with adding some quality points to the top end.


I believe modern combustion chambers are most accurately described as semi-hemis. They are much shallower than the old Chrysler engines he’s referring to, which needed pop-up pistons to achieve the desired compression ratio.


The correct terminology is a “pent-roof” combustion chamber, and it is the standard shape in basically all modern engines

Hemispeherical combustion chambers are, contrary to the popular belief, not ideal from a combustion efficiency (and by extension, power) perspective.


toyota did use hemispherical chambers until the late 90s in different series of engines, but not in many cars, and yeah theres solutions above in regards to just quality points

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