My 2001 Outback engine has started to rattle. It has a EJ251 (SOHC) engine. I have a couple of EJ25D (96 - 99 DOHC) engines hanging around. Can I combine these engines? EJ25D block with the EJ251 heads? I tried to research this but I'm still not sure.
4-bolt bellhousing on almost all 25Ds means you'll have to get a little creative on a second starter bolt (or hang the starter on just the upper bolt, it's been done). You'll also need to run the 25D headgaskets. They are thicker, as the 25D pistons protrude from the block at TDC, and will hit the heads with the 251 gaskets. Those are the only issues I can think of.
Yes, the short block fits... Swapped over the bracket that holds the timing belt tensioner. (SOHC rear timing belt cover is different) Swapped over the dipstick and tube. (mounts different on the SOHC head) Used the thick EJ25D head gaskets. Modified/adapted the PCV valve where it goes into the block.
Assuming it will work just fine the other way around? I just bought a 99 SOHC for my 98 outback (i plan on using just the short block with my 98 DOHC heads) should i use the newer head gasket or will the EJ25D gaskets work?
I don't remember the details off the top of my head, but maybe I can point you in the right direction. The SOHC shortblock with the DOHC heads is commonly used as a high-compression build. But I'm not exactly sure what head gasket combinations are being used for that, or how high the compression is. High enough you'll be stuck with premium gas, for sure.
^^ What Chux said. Using the EJ25D (thick) head gaskets will (probably) keep the valves from touching the pistons. I do not know what compression ratio you will end up with.
hmmmm, well long story short the car has 116k on it i paid $150 for the car with a rod knock, found out the motor is pretty much toast. Bought the SOHC motor off musashi on here for $300, looking for a cheap flip or a decent daily. I am going to read more into that high compression build though i haven't had to pay for premium since my bug eye might be worth a learning experience. thank you.
I was hoping so, i have a couple extra EJ25D MLS gaskets laying around i havent used yet. Like i said im going for the cheaper side of things. I thought the EJ25D blocks were the ones you had to worry about the pistons poking out? Probably wrong about that but i feel ive read it somewhere. hard sayin not knowin.
Yep, theoretically the thinner 251 gasket would run, but might be higher compression than you want. But I'm also concerned what compression the thicker gasket would yield, knowing that the piston height at TDC is lower, using the same gasket might yield a much lower compression ratio, which could make for a dog.
well im glad i have a job with internet access ive been reading forums on this high compression build all day from what ive gathered the EJ25D gasket will in fact turn her into a dog, ive heard good things about using 04-07 STI spec gaskets... any thoughts on that? It should put me around 10.3:1 and keep the quench just about right. Like i said though just random stuff ive gathered reading random legacy and forester forums...
Sounds about right. 10.3 is higher than stock, and will require premium gas. It's a good option, just be aware what you're getting into.
