Hello Prius Chat members, I am fully involved with a DIY cylindar head gasket repair. I have the head back from a machine shop and it all looks pretty good. It's pretty eash to tell when the crank is TDC. But, there is not much information on this smaller chain. Many of the videos do not even pay attention to the relative position. There is one post on prius chat that which refers to the reationship. I have rotated the engine not several times and have the small dot alligned on the lower gear and the tooth is very close on the upper. maybe half a tooth off. There does seem to be a small triaangle stamped on the large gear with the holes. A stamp like a small triangle which is perfectly alligned with the top link. Question. Must the valve train be in specific time with the lower for balance purposes? Is my position correct. Some have mentioned that every nine turns of the crank is when you get both yellow marks aligning on both sprockets. I believe the larger sprocket with the sqared off teeth if for crankshaft position ? BTW, I did not disasssemble any part of this lower assembly. Finally, because the chain is on I can's see and marks on the upper inner sprocket. Just the triange mentioned . I'm guessing this is correct. Many thanks to anyone with posses these details. Hirsh
Last link in my signature is the full engine section from Repair Manual; might help. (on a phone turn it landscape to see signatures)
Wondering why on earth the oil pump needs to be timed has been kind of a running gag around here for a while. As far as I can tell, nobody knows. But there are marks, so if you do it right, they look like this: "There's yer problem, buddy ... the oil timing was off!" No: that's every nine times you see the painted chain links go by. That's the same as seventy turns of the crank (or thirty-five turns of the camshafts). And that's for the valve timing chain. I don't know that anyone has worked out how often the oil chain marks line up. If somebody wanted to, it'd just be a matter of doing the math.
Well, I studied all the available information and reassembled the engine. I never removed the oil pump chain but kept turning the crank until the bottom yellow link aligned with the dot on the sprocket. The video listed above made it easier to time the cams to the crank. As you turn the crank to release the tensioner you wait forever to see the marks looing like the installation position. But the count! and the position of the cams will always align correctly at TDC. The videos by Nutsabout bolts are excellent. I had the head milled flat and tested at a maching shop. Used the Fel-Pro gaskets. Fel -Pro head bolts. Engine runs like a top. It took quite a bit of pacients.
