Timing alignment marks

Joelson317 · Post by **Joelson317** » 01 Dec 2018, 16:15

Hello,
I've got a question... if I may.

If the crankshaft to camshaft ratio is 2:1 and you are starting from scratch how do I now what rotation the crankshaft is on? First or second time rotation, in regards to ratio...

Did that or does that make any sense?

1998 V70 base, engine serial number: 1444104

Any information would be greatly appreciated.

Thank you,

J

Post by **rspi** » 01 Dec 2018, 17:48

Does NOT matter.

Post by **RickHaleParker** » 01 Dec 2018, 18:15

The ECM determines if it is a compression stroke or exhaust stroke by the position of the camshaft and other data. Get the Crankshaft, Camshafts in mechanical alignment, the ECM will deal with the rest.

There is only one mechanical condition where the three timing marks line up. Just make sure the camshaft pulleys are correctly aligned to the camshafts.

The process actually has two datums, the alignment of the crankshaft and the alignment of the camshafts from the rear of the cams. If you look at the rear of the camshafts your see the alignment slots are offset. With the slots offset, there is only one way the cams will matchup with the camshaft alignment tool. This is how you insure the cams are in the correct cycle.

On the intake side the alignment slot is above center and horizontal when correctly aligned.
On the exhaust side the alignment slot is below center and horizontal when correctly aligned.

Post by **j-dawg** » 01 Dec 2018, 18:37

To phrase it using the language of the original question: in the power cycle, the first and second rotations of the crankshaft to which you refer are geometrically identical.

Post by **abscate** » 02 Dec 2018, 05:14

Just adding the obligatory reminder to these threads that the valve timing marks on the crank and cams are NOT top dead center marks, but non- interference marks of piston and valves.

Post by **jimmy57** » 02 Dec 2018, 07:04

The features of the crankshaft and positions of pistons in the bores are the same when the crank marks align on every rotation so there is no difference for the crankshaft on either of the two rotations. The valves being actuated for their functions only coincides to the same event every second crankshaft rotation. The valve opening/closing only needs to happen the same on every second crank rotation.
So

dobrosailor · Post by **dobrosailor** » 03 Dec 2018, 04:52

abscate wrote: ↑02 Dec 2018, 05:14 Just adding the obligatory reminder to these threads that the valve timing marks on the crank and cams are NOT top dead center marks, but non- interference marks of piston and valves.

Boy I dodged a bullet here. I assumed the timing marks were for TDC on #1 and because I couldn't get my harmonic balancer off I couldnt' find the lower timing mark. I used a depth mic to find TDC on #1 but I play music with a Volvo mechanic friend told me there was a visible timing mark on the balancer and I finally found it and got it all aligned using the timing marks as opposed to having to use a cam tool on the other end which I do not have and did not want ot spend an afternoon fabricating one. Car seems happily timed - that coudda been ugly...

Post by **abscate** » 03 Dec 2018, 05:08

Yeah, that's about a $2000 mistake