Thread: Cams + Crank Timing Chain Question..Mating Marks..

Hey,

I was wondering if it could be possible that the timing chain marks line up for the camshafts but the timing chain mark on the crank could be wrong?

Is this possible? If so, how? I'm not understanding the mechanics behind this. I'd guess if the camshaft timing marks on the chain were off so would the one on the crank and visa versa if you see good timing chain marks on the cams then the crank must be good?

As always, thanks for the help!

-G

are you talking about the odd-colored links lining up with the marks on the gears?

If so, if intake and exhaust both line up, the crankshaft one should be lined up as well. You might have one of the camshafts line up and the other not, in which case it's got the wrong link on it and the crank won't have it's line up either. But you might have situations where they are off by just a bit, but everything is still sound mechanically just because of the natural drift of the chain vs markings.

For this reason, along with the constant rotation of link locations and the difference in rotation of the crank vs camshafts, you only use the colored links on the chain during initial assembly. Once the motor starts spinning, they're virtually useless.

Hope that helps a bit.

Ya, I'm talking about the colored marks. Hmm, I didn't know that was just for installation. I have read that if you turn the crank enough times the colored marks should line up. Is that not true?

-G

Yes the two cam sprocket marks can line up but the crank marks can not line up. If they are off by one tooth on the crank I think that is 20 degrees of cam timing that you'd be off.

Yes if you turn it enough they will all line up again. It can take over 100 turns to get them to line up again though I think.

Yes it can happen. You need to make sure the piston is at TDC which just look at your crank pulley and line up the pulley mark 2nd one from the left if on a stock crank pulley and then check your dowel pin positions and make sure your at 12 oclock on the exhaust and 10 oclock on the intake and that there are 20 pins between the dots. Simple as that.

but you would notice the crank key/mark not be at 12 o clock right? or would you only be able to see it by taking the cover off and looking at the actual chain on the crank?



I'm wondering if you get the cam timing correct, if the crank can still be off.

Setting the cam timing correctly involves making sure that piston 1 is at TDC. If you do that properly, there's no chance that the crank/chain can be off.

So it's not possible that the cam timing looks correct and at the same time the crank is off a tooth?

In other words, you can check whether the crank is off a tooth by making sure the cam timing looks correct.

Reason I'm asking is because I recently went to the dyno and it appears I'm losing 30-40whp somewhere/somehow. I've always had a strange advanced timing to get 15* on this car since I received the motor. Same thing after S4 cam install about a year ago eventhough we confirmed cam timing like 4 times. It makes me think it's off a tooth on the crank possibly as has been suggested by a friend.

-G

If you're checking your cam timing by putting cylinder #1 at TDC and then comparing the two cam sprocket/chain positions and everything checks out then you're fine. If piston #1 is not at TDC during the check then you have a problem.

You sure your crank pulley hasn't separated?

Ya, every time we were checking it we made sure it was at TDC. I guess I'll open the VC 1 more time to check things out so I can rule out the timing issue. I still have no idea why I have to advance the distributor so much to get 15* It was like that when I received the motor as well from Japan.

This car's a mystery. Once I get the dyno sheets from the dyno shop I'll post them up. Some strange stuff going on w/it. Note to self: Bring a USB memory stick to put dyno graphs on.



Crank pulley is fine.

-G