Kostamojen Posted April 17, 2010 Author Share Posted April 17, 2010 Alright, I went back to the machine shop to discuss the piston. He basically said he doensn't think it will be an issue considering he doesn't think the CR will go that high. I told him i'd go do some maths and get back to him on that... So, I just did a "ghetto" CC measurement of the combustion chamber (using a syringe, some gatorade, a straight edge level and a toothpick). The results were: The combustion chamber is approx 30-33cc Removing 2mm from the combustion chamber makes it approx 21-24cc Using this compression calculator: http://www.csgnetwork.com/compcalc.html And the associated required information - Bore x stroke - 85mm x 60mm Gasket bore - 85mm (measured it) Compressed headgasket thickness - 2mm Piston dome volume... Zero I presume, but there is a little space around the edge of the piston, possibly worth a couple cc Piston deck clearance - 0 (its flush with the deck) The worst possible scenario i've come up with is a CR of 11.5:1 The best possible scenario i've come up with is a CR of under 10.0:1 An average of the two puts it in the mid-high 10's, 10.5:1 or so. Quote Link to comment Share on other sites More sharing options...
Don_Quixpunch Posted April 18, 2010 Share Posted April 18, 2010 I don't think 10.5:1 is too high for premium pump gas. Sounds like you have more knowledge there than I have. Quote Link to comment Share on other sites More sharing options...
Kostamojen Posted April 18, 2010 Author Share Posted April 18, 2010 The machine shop did say they could "dish out" the piston of CR ends up being too high. Quote Link to comment Share on other sites More sharing options...
Kostamojen Posted April 18, 2010 Author Share Posted April 18, 2010 I just double checked something, realized I made a couple errors. 1) The EA63 1400 2-port head has a slightly LARGER compression chamber. That was the head I was using for CC measurements because its still assembled: What that means is that the CR is probably higher than I calculated. Probably about 5% less CC is my guess. 2) The piston isn't completely flush with the deck, its about .5mm lower (checked with a straight edge and feeler gauge... not perfect but worked) So I'm going to run some calculations again to see what I come up with... Quote Link to comment Share on other sites More sharing options...
Kostamojen Posted April 18, 2010 Author Share Posted April 18, 2010 The uneven port overlap will indeed hurt overall airflow, but just look at the flow path once it gets past there. IIRC, the EA81 head has 12 turns from intake gasket to exhaust gasket. Ideally, there would be less than five. I was taking pics and realized I didn't have any showing the intake/exhaust port flow of this head, so here you go: That makes for a total of THREE turns for the intake from the carb to the combustion chamber. The exhaust port is one turn, basically straight out the side. Plus, I took pics of the gaskets for your amusement... The exhaust gasket could actually be matched a little better: Quote Link to comment Share on other sites More sharing options...
True2Blue Posted April 20, 2010 Share Posted April 20, 2010 (edited) CLICK THIS they can do anything Subaru engine. and will have answers for your many questions:grin: Edited April 21, 2010 by True2Blue Quote Link to comment Share on other sites More sharing options...
Kostamojen Posted April 21, 2010 Author Share Posted April 21, 2010 RAM is quite expensive, more expensive than my local machine shop that can do basically the same things (minus the fancy pullies and what not) Quote Link to comment Share on other sites More sharing options...
ShawnW Posted April 21, 2010 Share Posted April 21, 2010 Can't wait to see a post saying its running. Quote Link to comment Share on other sites More sharing options...
Kostamojen Posted April 21, 2010 Author Share Posted April 21, 2010 Can't wait to see a post saying its running. Hey shawn! Its probably going to be awhile... Quote Link to comment Share on other sites More sharing options...
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