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Does anyone know the official combustion chamber volume of this head? I've seen either 50cc or 53cc posted on the internet, but nobody has posted anything concrete.


So has anyone out there actually cc'd this head, or know where I can find something from subaru stating the specs for it?

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I think it's 46.2 for EJ25D

50 for Phase II EJ25 (and some turbo EJ25 heads)


1996 EJ25 FSM shows bore and stroke and compression ratio:  99.5 x 79, 9.5


I'm unsure of headgasket thickness, the 610 EJ25 headgasket is 1.52mm thick, but is that a revised thickness or same as the originals?


When back-calculated using 1.52mm headgasket the head volume is 46.2


If you back-calculate using .58 mm headgasket thickness (like Phase II EJ25's) - then that gets you in the 53cc head volume, but i doubt the original EJ25D headgaskets were thin - were they?

Edited by grossgary

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