It has been widely reported that ej22t Pistons protrude the deck by 0.5mm, yet at least one individual, FujiK on Nasioc, has run the thin ej22e metal head gasket with USDM WRX heads and a stock ej22t short block.
Now my own measurements with some admittedly crappy instruments have determined that the pistons do not protrude anywhere near .5mm.
My measurement procedures were as follows:
Engine was brought to TDC on all 4 pistons, one at a time.
A metal ruler was laid on edge across the piston crown.
Feeler gauges were inserted between the deck and the ruler until the gauge wouldn’t fit.
My conclusion was that anything larger than my .28mm feeler gauge would not fit between the ruler and the deck.
I by no means assume that my instruments or method were executed/used without flaws but only to the best of my ability.
To improve my method I would need to verify my feeler gauge thickness with a micrometer and perhaps use angle and depth gauges to determine TDC more accurately.
Now using the following information if we bolt ej25d heads to an ej22t short block:
Cylinder bore: 96.9mm
Stroke: 75mm
Headgasket bore size: 97.5mm
Headgasket thickness: 0.58mm*
Head compustion chamber volume: 46.6cc*
Piston Dish: 28cc*
Deck protrution: 0.28mm
*provided by ejcalcs
I used this site to calculate the compression ratio:
http://www.csgnetwork.com/compcalc.html
We get a VERY boost friendly 8.19:1 compression ratio.
If we use the stock headgasket it works out to 7.59:1 compression
Comments?
errors?
Kaz
