How to do TDC and correct timing

N370

So I recently took out the timing chain cover along with the timing chain in order to change the oil gallery gaskets. After removing and then reinstalling everything back I found out that the timing was a little off. Can someone with better knowledge walk me through on how to properly setup (TDC) top dead center on the camshafts.

RDWizard

Did you ever get an answer? I'm in the same predicament now.
I'm trying to check my timing before I pry off the cover.

SouthArk370Z

First place I'd look is the FSM (link in my sig).

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jmroy6

On each cam sprocket there are timing marks located on the back side on them. line up this dot with the timing marks on the chain, once you know the crank has been placed at tdc. i can send pics later.

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2012 370z GTM SC

elhombre

This is more for people to do before they take things apart...


Find cylinder #1 take out the spark plug, stick a long allen key into it. Rotate the crank shaft until the allen key has reach a peak point on the compression stroke (ie all valves closed in cylinder 1). Stop there, then go to your camshafts, locate the markers for TDC make a note of where they are in relationship to the factory specification for alignment (on the heads) and also look at the crank pulley, there is probably a mark for the TDC.

When I do a motor I like to take a white paint marker and mark all of my moving timed parts to a fixed location so that when I put it back together I don't have to worry about making a mistake.

RDWizard

The real question for everyone is how many crank rotations can it take to line up all the timing chain marks up properly?

The answer is NOT in the FSM!!!
I will provide pictures and the answer when I get to my PC.

TDC is easy.
The diagrams for the timing chains ARE in the FSM.
Nowhere can you find how many crank rotations it can possibly take to match TDC and all the timing chain marks.

SouthArk370Z

It's a 4-cycle engine - 2 rotations. The piston will move to the top twice but only one of those will be TDC (both valves closed).

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RDWizard

Yes. That is correct for TDC but not for Timing Chain Alignment.

phunk

Ill give it a stab without a lot of thought, but I warn I do not practice math much at all... but maybe...

Where x = timing chain links, and y = crank sprocket teeth

lcm(x,y) / y = revolutions between timing chain eclipse

anyone good at math? grade me

edit: never mind i just graded myself, i get an A+ this solution works.

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RDWizard

For the sake of science (And because I couldn't find it anywhere on the internet) I counted the required revolutions of the crank between true complete 100% Timing Chain Alignment Check at TDC as per the diagram in the FSM.

1. Every 22 revolutions of the crank, the double orange links on the secondary timing chains line up with the proper dimples on the outer cams at TDC.

2. Every 1100 revolutions of the crank, the yellow links on the primary timing chain line up with the proper dimples on the inner cams at TDC and the double orange links on the secondary timing chains line up with the proper dimples on the outer cams.

That's once every 50th time condition 1 happens, condition 2 will happen!!

So if you're checking your timing, you may have to rotate the crank anywhere up to 1099 revolutions to check it.

Helpful Hint: Remove the sparks plugs before starting. It makes it a hell of a lot easier. Doh!

Attached Images

Timing Chain Alignment.jpg (198.0 KB, 36 views)

phunk

My formula fell on deaf ears

Where x = timing chain links, and y = crank sprocket teeth
lcm(x,y) / y = revolutions between timing chain eclipse

solution: lcm(100,24) / 24 = 100 revolutions of the crankshaft per full timing chain alignment phase.

edit: ahh you are also trying to achieve simultaneous alignment with the secondary chains as well... I had not factored that in yet. Now I am intrigued.

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Spooler

Put the car on TDC per the crank pulley. Take front cover off. Check and see if the mark chain lines up with the dimples on the crank and cams. If so, take apart. If not, rotate engine to desired marks are line up. Easy, use to do this all the time with VG30DE, KA24E, SR20DE's, etc. make sure you have it right before taking anything apart. If you are not sure, take to someone who does know.

TechnicZ

Whenever you're are removing a timing chain or belt. You always need to bring cylinder 1 to top dead center. There are timing marks when you remove the timing cover stamped onto the cams and crankshaft to help align to the back timing cover. At this point always look for golden or brass colored links bc these are the links that are supposed to go on these marks. Once in a blue moon you'll have time line up initially but as long as you are TDC cylinder 1 you can remove the chain and put it back on with the links matching up and it will be on time.

Sent from my SM-N950U using Tapatalk

phunk

^^ exactly, there is no purpose to spinning the engine until the timing chain marks are aligned. Just make sure cylinder 1 is TDC and you are safe to take it apart.

The colored links on the chain are intended to aid in assembly, not disassembly. As I mentioned a couple posts up, it can take up to 100 rotation to get the colored marks to line up again just on the primary chain not considering the secondary chains.

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TechnicZ

Have you ensured proper alignment of the timing marks on the camshafts and the crankshaft? Once these are aligned, put the main timing chain on the top cams first and ensure the colored links are in place, then carefully line the crank sprocket and chain up, hold this in place and then put the chain tensioner, with tensioner guide, in. Then put the secondary guide on the other side of the motor on and relieve the tensioner. It's finicky but once you get the hang of it, it'll become a nice technique to master.