Bumping the famous Frankenstein post because I purchased a $500 '97 Wagon that needs an engine (came with a motor that had its crank pulley WELDED on and wobbly, crank and shortblock are ruined) and I wanted to go through absolutely all the information available in order to decide what to do with an engine for this car. It also came with EJ22E heads (dual port) and not EJ22EZ heads (single port) like it was supposed to, so this is a good opportunity to try another Frankenengine...
Anyway, I have a set of EJ203 heads sitting around, along with a EJ251 head I borrowed from a friend, plus these EJ22E heads. I decided to measure the combustion chamber volume myself to confirm numbers online, plus get numbers for the 203 since nobody has done that yet.
I'd like to eventually get my hands on an EJ18, EJ22EZ and EJ221 head to get measurements on those too, as well as get the cams/lifters off the EJ22EZ head for my EJ22E heads. Here is the page with all the information I've collected so far:
Let me know if you have any first hand measurements, especially for piston volumes and deck clearances. Those are really hard to get numbers for.
I wanted to go over some differences that are mentioned a lot but never really shown, especially between the Phase 1 and Phase 2 SOHC heads. This information is readily known by people who have worked on these motors, but I'd like to document it so people that don't have the engines in front of them can understand.
Phase 1 heads have limitations, mostly due to the location of the spark plug tube directly impacting and limiting the intake port size and shape. The fact that the cams have to slide through the head casting itself with Phase 1 SOHC heads means the maximum lift of the cam is limited. Phase 2 heads with the separate cam carrier case lets them run significantly more lift on the cams, including large lobes for aftermarket cams.
I wanted to go over some information about the EJ202/3 heads that isn't discussed much. 202 and 203 heads are fundamentally the same from what I know, as the first motor I purchased awhile back was an EJ202, and the second was an EJ203. These heads are the same design as EJ251 heads, but with smaller valves, 3cc less chamber volume, and cams that have less duration but the same lift. The intake port is slightly smaller with the EJ202/3, but the exhaust port is the same.
Finally, I wanted to go over theoretical builds using Phase 1 heads on an Phase 2 block...
My first use of mixing blocks is mentioned in this thread, running EJ202 heads on an EJ221 short block. Compression wise, this combination reduced chamber volume by 3cc. According to what math I could do, this would bump the compression from 10.0:1 to about 10.5:1. A nice mild bump in compression. However, there is a reduction in valve size supposedly, as well as possible differences with the cam shaft. The engine is still running with two different new owners and running well, so I would consider this a successful "mild" Frankenstein engine, with the ability to change out to dual port headers rather than the EJ221 single ports.
My second use was running EJ18 heads on an EJ203 short block. This is supposedly a reduction of 7cc to chamber volume, but I haven't actually measured the EJ18 heads. Theoretically this would bump compression to around 11.0:1 according to what math I could put together. It was a very healthy motor, and did a couple track days + autocross days with it before removing it for a WRX swap. I even had it dynoed:
Looking at my EJ22E heads and my options for the '97 wagon, the chamber is plenty small enough to clear the cylinder walls and gasket from an EJ20.
This means that EJ22E, EJ22EZ and EJ18 SOHC heads should all be able to be used on an inexpensive JDM EJ202/3 in order to create a higher compression motor utilizing Phase 1 equipment. SUPPOSEDLY EJ18 heads have the same CC's as EJ22E/EZ heads, but I can't confirm that until I have one in front of me.
As the rest of this thread has gone through, running Phase 1 heads on an EJ221 or EJ251 short block bumps the compression ratio to 11.5:1 or even higher. EJ221's can only be bought at junkyards now, and JDM imported EJ251's are twice the price of EJ202/3's now, and you can buy a new EJ251 short block for $2k from Subaru.
Also a note... For those who run or want to run EJ251 heads on EJ22 short blocks, the chamber diameter won't be too large for the headgasket/cylinder walls of the 2.2l short block. However, there is NO REDUCTION of compression ration as supposedly the EJ221 and EJ251 have the same chamber volume. I need to measure an EJ221 to confirm this though.