October 27, 20169 yr They're multi layer steel, the stock ej251 gaskets are single layer and are prone to failure in the form of leaking coolant and oil along the bottom of the head/block seam. I've done somewhere in the neighborhood of 75 head gasket jobs on the ej251/3 engines using the 04-06 sti gasket and never had a repeat failure, which is still an issue with the oem replacement ej251 gaskets.
October 27, 20169 yr Author Seems like the EJ25D heads on the EJ251 block would be a nice little NA setup if you drop it in an early year 5MT. I'll think about doing this if I can find a deal on those heads. However, my gut feeling is it would be cheaper to just get the whole EJ251 longblock from a Pull-a-Part and just use the Delta 220 regrinds. Edited October 27, 20169 yr by janas19
October 27, 20169 yr If you can find a pick a part with both a 25d and a 251 you could make the hybrid there. Pay longblock price for it and pit it together with new gaskets and such afterwards. Just make sure you keep the dohc head bolts with the heads, sohc head bolts are longer.
October 27, 20169 yr Author Bahahaha. Build a hybrid in the junkyard ground? I love it! LOL Dude, you get a gold star. This is genius!
October 27, 20169 yr Author So I didn't know this but there are factory hybrids. The 98 2.5RS has the Phase II block and DOHC heads. Rumor is the 98-99 Outbacks also have the hybrid engine: I was recently informed of this fluke by the folks a Colorado Component Rebuilders who do nothing but rebuild EJ's all day long. For some reason the '98 and '99 Outbacks got the phase II shortblocks but continued to use the DOHC heads... Can anyone confirm?
October 27, 20169 yr Sort of... After engine #2213362 (manufacture date sometime in 03/98, which would primarily be '99s, maybe a few '98s), the OE catalog shows the #5 thrust bearing. The '99 SUS I had, definitely had a phase 2 style timing belt tensioner. But, all '97+ 25Ds show the same part number for pistons and all 25Ds with the same head gaskets. Which is why the compression isn't higher.
October 27, 20169 yr Bahahaha. Build a hybrid in the junkyard ground? I love it! LOL Dude, you get a gold star. This is genius! It's more common than you might think.. Find an old work van and set up shop in the back.
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