Cam to crank timing

Exhaust cam sprocket should have a dash at 12 o'clock.

Intake cam sprocket has a "tab" sticking out at around 2 o'clock. Note: I installed the newest revision intake cam gear on this engine, so yours may be different.

If you use the colored links on the chain, the backside of the intake cam sprocket should have a dot that corresponds to the colored link on your chain.

Picture for reference....ignore the red circles. I was trying to show someone the location of the T-Joints where these covers always leak from.

 

Hindsight is twenty-twenty, but: Toyota should have put info like this in the turd gen Owner's Manual...

(The "head gasket" links in my signature may have this info (in Repair Manual excerpts), but buried/disorganized. There is no "head gasket change" section in the Repair Manual, so I pulled together a mish-mash, various pages from the engine disassembly section. If needed I can dig some more. )

 

The easy answer to the OP is that (as I understand it) the sprockets are the bits that have to be in fixed time to the crank, and the sprockets are where the timing marks are, so if those line up with the marks on the chain, you're good.

The intake sprocket only allows the cam to be advanced by a certain amount, not enough to lead to mechanical interference. If the cam is not in its fully retarded and locked position with respect to the sprocket right now, it should get there as soon as the sprocket starts turning when the engine is cranked.

If you don't want to trust that, and you have the valve cover off, you could use a wrench on the camshaft flats and turn it a bit in the retard direction until the sprocket locks.

 

Not exactly. This is true for the exhaust cam and the crank, but the intake cam doesn't have obvious marks (most people don't know about the dot on the backside) so it is entirely possible for the intake cam to be "off."

 

How does what you are saying support your conclusion?

The intake sprocket is pulled around by the timing chain, in fixed time to the crankshaft.

The intake camshaft is able to move through a range of 33° with respect to its own sprocket, so it can open anywhere from 15° ATDC to 18° BTDC.

The timing marks that the repair manual tells you to look at are on the VVT-i controller housing, which (in the illustration I am looking at) rotates with the sprocket, not with the cam, so the marks are where they belong.

Edit: the illustration I was looking at was in the Gen 1 New Car Features manual, but we've got a PriusChat thread (here) showing the Gen 2 sprocket/controller disassembled, and still the cam moves with the inner vane, and the outer housing with the timing marks stays with the sprocket where it belongs.

In that thread, the poster identifies a punch mark you can see through the center hole of the cover plate, if you want to find where the home position is. If you haven't, though, when the chain first starts pulling the sprocket and there is no oil pressure between the vanes, it is going to find that spot.

 

Not sure if we are talking about the same thing.

For assembly (and discussion) purposes, the VVT actuator is locked to the camshaft. It is not possible "unlock" the actuator very easily; there is a specialized procedure involving shop air and taping certain holes to unlock it. Not the point of this discussion...

I think the OP was simply asking for direction on how to properly time the exhaust and intake cams with the crankshaft. My reply was: the exhaust cam is fairly straightforward - just look for the dash at 12 o'clock. But the intake cam can be tricky since it is entirely possible to install it 180 deg's off if you miss the hidden mark on the backside.

 

Maybe we're not talking about the same thing,

The intake timing mark that the manual tells you to use is a long groove that is machined in the outside of the intake adjuster housing. It lines up with the pair of colored chain links.



When you say "it is entirely possible to install it 180 deg's off if you miss the hidden mark on the backside", are you saying there is an identical groove halfway around the adjuster housing that could be mistaken for the timing mark?

 

Yes, there are similar marks 180 deg from this location that can be mistaken for this mark. But backside of the intake sprocket has a tiny dot in the correct location. However, this isn’t mentioned in the repair manual.

 

I see about the extra marks 180° away.

I think you're still ok with what the repair manual does mention, because it shows the positions of the no. 1 cam lobes.



Even if you haven't locked the sprocket, so the intake lobe could be as far as 33° further advanced (it might look closer to straight-up than northwest as the picture shows), still if it were 180° off (somewhere between southeast and straight down) that would be pretty obviously wrong.

 

Where can I purchase the VVT sprocket for a 1st Gen 2003 Prius?

 

I think that's first gen. Would be better to post a new thread, here:

Generation 1 Prius Discussion | PriusChat

That said, you'll probably do ok here, get responses.