Cam shaft and Crank Shaft Notches not lining up - 2012 Prius

Please let us know an exact distance/measure/photo for: "they are not lining up"

How much work was done on the head before it was put back together?

 

The timing chain is the same for all Gen 3 Prius'.
He will have to manually set the crank to TDC, and align the cams to the correct
location, then install chain aligning the gold color links...

 

That is not true. There is no floating. There is variable valve timing.
The initial timing marks must be set correctly. After that, it's automatic.

After setting the chain, and releasing the chain tensioner, if you rotate the crank 720 degrees,
two full turns, the timing marks should line up. The colored links won't, unless you keep rotating the
crank about 30 times, at least that's what was posted on here.

 

On a gen 3 Prius, it's 35 cam revolutions, which is 70 crank revolutions; that's been posted on here several times.

The description given in post #3 of a 'hunting' system (interesting term, hadn't heard that one before) simply refers to the math that is behind those numbers, covered in older posts here and here.

As explained there, the choices Toyota made did not "maximiz[e] the least common multiple"—if they had made the chain two rollers longer, you would need 142 crank revolutions to line the marks up again!

 

That is pretty complete ... though it doesn't offer any answer to the frequent question "how come the marks aren't lined up every time they go by?".

But of course we have those old posts here for that.

Edit: tube -> time

 

Did you get the timing set?

 

Glad you got it going!

 

I always wonder why anyone goes to the trouble of making a video on why something happens that stops so far short of explaining it.

At least he gives the basic idea of not having the same chain links always hitting the same sprocket teeth every time around. But the explanation "they make the gears slightly offset, so as the belt comes around, it is hunting" is just handwaving. What would "gears slightly offset" even mean? The video explains nothing about the simple matter of how the number of sprocket teeth relates to the number of belt lugs or chain links, and so doesn't tell you a thing about how you can know the number of revolutions required (other than the brute-force "try it, and count" shown in the video).

The Honda Civic timing belt in his video is seen to come around to the marks again every 52nd full turn of the camshaft (which, of course, is the same as every 104th full turn of the crankshaft). The video also shows (though he didn't point it out) that that's every 19th time the mark on the belt comes around.

You can count the teeth of that Civic cam sprocket; it's got 38 of them, so you know the crank sprocket has 19—it will always have half the teeth of the cam sprocket, because the crank always goes twice around for each turn of the cam. (That also tells you a cam sprocket always has an even number of teeth—if you count an odd number, count again.)

If you pause the video the first time the belt mark comes around again, that's after the second full turn of the cam sprocket and on the way to the third. The belt mark is then 10 sprocket teeth ahead of the sprocket mark. We've just counted the lugs in the belt! Two full cam turns (2 ✕ 38) plus 28 (that's 38 − 10, 'cause the belt mark came around 10 teeth earlier than another full cam turn). That belt has 104 lugs.

104 is 2 ✕ 2 ✕ 2 ✕ 13.

38 (Civic cam sprocket teeth) is 2 ✕ 19.

The only factor common to both 104 and 38 is a single 2, so 2 is their greatest common divisor.

If you multiply 104 ✕ 38 (3952) and then divide by 2 (the GCD), you get 1976: the least common multiple of 104 belt lugs and 38 cam teeth. That's how many total lugs have to pass before the Civic marks line up again.

1976 lugs ÷ 104 (the length of the belt) is 19, the number of times the Civic belt mark goes by.

1976 lugs ÷ 38 (teeth in cam sprocket) is 52, the number of full turns the Civic cam goes around.

1976 lugs ÷ 19 (teeth in the crank sprocket) is 104, the number of full turns the Civic crank goes around.

... and that's the way it's done.

If you do the same math for the sprocket teeth and chain links for the gen 3 Prius,
you get 9 times the chain marks go by, 35 full cam turns, 70 full crank turns. That's the math that was already covered in older posts here and here.


The thing I most dislike about the video is the way he winds it up like this:

it's designed to be 'hunting', so it's ever so slightly off. Hence the reason why those timing marks may be ever so slightly off when you go to line them up. Now, granted, if they're a tooth or something off, then you should do what you can to address that. However, if it's just a little bit off, by a few millimeters, don't sweat it, it's designed to be 'hunting', that's the way it's supposed to be​

That's a useless way of thinking about it. Notice the first time that Civic belt mark came back around, it was nothing like "a little bit off", or even "a tooth or something off": it was ten teeth off (ahead of the cam mark). If you ran it around one more time, you would find it twenty teeth ahead (or 18 teeth behind). Another full time and you'd find it 8 teeth behind, and next time it would be two teeth ahead, and so on.

Those positions are all correct (for the corresponding number of times around), even though they're a lot more than "a few mm" or even "a tooth" off.

Conversely, any other position would be wrong (for the corresponding number of times around), even if only "a tooth" off. (Anyway, how is a lugged belt or a chain ever going to be "a few mm" off, or anything besides a whole number of lugs or links?)

The fact that the design is 'hunting' doesn't mean you should just shrug off the discrepancy if the marks don't line up; it means you should know exactly what to expect, and expect exactly that, or fix the problem.

More on the kind of math that's involved above can be found here: Modular arithmetic - Wikipedia