Basiacally, as per the title, i have a JDM SF5 forester, with a spun big end bearing in the stock open deck EJ20G. Found a replacement engine, however it is an EJ205. Will my current ECU handle the EJ205 if i were to drop it straight in? and if not, what would be the simplest route to making it work? I have decent EJ20G heads, intake manifold etc if required. Or will a piggyback ecu be required?
Put the EJ20G heads and intake manifold on the EJ205 shortblock. That's the easiest way.
yea i figured that would be best. One thing though, I keep seeing posts saying the pistons at TDC are above the surface of the block, but these posts seem to always be in reference to the closed deck variety 20G. IF this is true, do i just use a 205 head gasket? as if this is the case and i use the gasket designed for the 20G heads ill lower compression, which i imagine may have implications with the stock ECU?
The EJ20G pistons are slightly above the deck. The EJ205 aren't. The compression will change some. You have to do the math to see how much, then decide which gasket to use to get it where you want it to be.
any idea what the tolerance is? i can't seem to find a number anywhere