My memory is a bit fuzzy but i seem to remember the 6 head bolt situation beginning with the 2.2 engines and carried forward from there. The prior 1.8 push rod and 1.8 OHC engines used 8 bolts. Those were relatively problem free.
Another point I might make and I suspect this is due to no head bolt retorque. As you know, the Subaru cylinder heads are very short in length. Logic would dictate that a very short head such as this would not easily warp.
The majority of heads I’ve removed were out of spec and needed to be surfaced. Spec is .002 and I’ve seen some in the .010 or better range. Those were often on the borderline as to whether or not they would clean up as .020 is the maximum allowed for material removal.
At one point back in the 80s Subaru would actually pay the dealer mechanics to retorque the cylinder head bolts at 1000 miles. These engines were bulletproof, short of overheating.
I don’t really buy that the open block is the cause of the problems. Until 1977 Subaru blocks were open blocks and referred to as wet-sleeve engines. This meant the cylinder liners were removed by hand or with a special tool.
These engines were very prone to head gasket issues but it was NOT due the open block design. It was caused by the fact that the liners sat on copper gaskets of varying thicknesses. The liners were designed to protrude above the block by .005 of an inch.
Copper being soft of course, it’s not difficult to see what is eventually going to happen when the copper crushes down like a penny on the railroad track…
Anyway, just some more rambling trivia for what it’s worth.
