Yes good thoughts there, it's only one cam that's hard to turn. I can I identify a faulty AVCS sprocket? And maybe the belt was new but the tensioner wasn't!   Many thanks for your opinion 

For chamber volume, if your heads are indeed 49cc, and you’re trying to calculate compression, you’d take the total displaced volume (including chamber volume) for one cylinder, subtract the chamber volume, and use the difference to determine the required gasket thickness. It’s worth noting that HF pistons are tricky to find data on, but they likely have a slightly higher dome or different design affecting compression—so factor that in carefully.

Hey, that pricing does sound reasonable if it's for a genuine Subaru part. Mechanics often charge more for OEM parts because they come directly from the manufacturer and are guaranteed to fit and perform as intended. While it's true that you can find the part cheaper online, keep in mind you'd still have to arrange for fitting, and some shops might not install parts you supply yourself. As for welding, it could be a cheaper option, but you're right to question if it would pass safety certification—it really depends on the part and the quality of the repair. If you're aiming to hit 200k, it might be worth investing in a proper fix to avoid any issues down the road.

Sure, I’ve got a few thoughts that might help ease your mind! The AVCS system could indeed be a potential factor here. If something went out of sync or malfunctioned, it might have caused interference that led to the failure. However, it’s relatively uncommon for the AVCS to fail in a way that would result in sudden mechanical breakage without some other warning signs like rough running or check engine lights. Another thing to consider is the tension on the timing belt. Even if the belt itself and the idlers appeared fine, an issue with the tensioner could cause the belt to lose proper tension, which might lead to a misstep, especially at higher RPMs. It's also worth double-checking the alignment marks to see if anything was slightly off during the most recent service.

As i mentioned in another post I've been cleaning and blasting parts so they dont have the labels on them anymore. Can anyone tell me how to tell which is which side and which end is toward the diff and which is at the hub end? The front lateral arms have a hole thru them and one has an "O" stamped beside the hole while the other has a raised dome. Cheers.