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If it's an '85 and still has it's cat converter, be careful. Too much zinc could ruin the converter over time. That said, in '85, the zinc content of oil had to have been higher than it is now? I'm not an expert in Subaru engines, but I know FLAT TAPPET (usually v8) engines benefit the most from zinc. In this case, if you have a flat tappet aftermarket cam, it's worth using it up to a point, especially with high valve spring pressures. I think the number people shoot for anymore is 1300ppm or so for cars with NO converter. The old Dino Havoline 10W40 runs almost 1000, and I wouldn't see that being too low. I ran Castrol for decades in an old Datsun, never added zinc, and never had a problem. Rotella used to be great, but they changed it over time, and the Zinc is sadly not what it once was. Valvoline VR1 is an awesome oil for classic cars that you can now buy at Walmart- I THINK it's around 1300 ppm Zinc. However, it states... "It is not recommended for vehicles with catalytic converters" https://www.valvolineglobal.com/en/vr1-racing-motor-oil-sae-10w-30/

Run diesel grade oil, it has the higher ZDDP levels. Example: Shell Rotella.

Moosens. Please take a look at the last image in my last post ".. and before I stuffed the sock in the intake port (to block dirt and debris) I looked down into it and I see a pile of "oxide crystals" https://www.ultimatesubaru.org/forum/topic/186408-ea82-replacing-manifold-gaskets

Got em all out without breaking any - I don't think Ive stripped the holes either but haven't cleaned it up yet. For this really tough bolt I decided to use a "paint stripper" heat gun on high for about 15 minutes and it still wouldn't budge so drilled a 2nd hole down closer to the threads, earlier had drilled a hole about in the middle of the column to get the penetrating oil down into the crud in the bottom inch of the column also. After drilling this second hole and then using a lot of penetrating oil, then heat, I had progress had to heat up down by the head for at least 10 minutes with paint stripper heat gun, that's why my aluminum shield has turned golden brown .. I tried a M.A.P. torch but it was to scary and causing way to much smoke for my comfort.. and wiggled back and forth tell I could get about 1/4 turn, came back next day tried it cold no t so much movement so heated it up again and kept working it back and forth - but not going as far in as out.. then add more sauce.. do it again and eventually.. Here's the bolt right after I got it out - I used a lot of B'laster penetration oil, and couldn't get it moving with the 3/8" impact gun - had to really push and pull on this ratchet - really hoping the bolt wouldn't break,, kind of amazed it didn't

I was gone for about 2 months and I finally got back to working on this car and ended up drilling a small hole on the outside corner of the manifold where the bolt goes down to try to get penetrating fluid or blaster down in there and then went and got myself a modern 225 foot pound max rigid torque wrench gun and I haven't broke any of the 3 bolts loose yet, so I guess I gotta go get me M.A.P. Torch, thanks for the good suggestions.

Just like @idosubaru says; Turn the bolt a little bit, spray the bolt head with PB Blaster or other penetrant fluid. Then torch the area of the head where the bolt is stuck with a map gas torch (handheld) Turn the bolt back and forth just a couple degrees again. Torch the area, spray with PB Blaster or dab on some candle wax while it's still hot. It will make the lubricant soak down to where it's needed. Keep repeating the process until the bolt frees up