Timing - Top Dead Center

[BigNiner19]

Can anyone tell me which cylinder/piston is "Top dead Center" for timing on a 2005 DF250? The marks on the camshafts are not lining up. I dont want to take a chance when I start this motor.

[BigNiner19]

Anyone have any input on the timing for this motor? I think it may be 180* off but the crankshaft position is matching the mark for TOP DEAD CENTER. But niether of the cams match there timing marks

Any suggestions to assure that I have matched and correct timing before I put it back together and start it?

[Harper]

I don't know a thing about the DF250, except that it costs a lot of money. So, be patient, as sometimes it takes a while to get an answer to some questions. A factory service manual is a really cheap investment for the DIYer, considering the cost of that engine you've got torn down.

[BigNiner19]

Okay, maybe an easier question. The manual says to match up the timing marks on the camshafts and the crankshaft. My question is, if all marks are matched up, would this be considered timing set or could there be other adjustments necessary to make the timing correct before starting the motor back up?

[Harper]

Okay. by this post I assume you have a manual, and that's good to know. Surely your manual has some illustrations of correct alignment. My 150 manual shows the timing marks on the crank sprocket and the cam sprockets, along with the colored links on the cam drive chain(s), and how they need to be aligned in order for everything to be right.

Pardon me if I seem to state the obvious, but I have no way of knowing your level of knowledge. Valve timing is critical to your engine's operation.

Cams turn at half the speed of the crank, so the crank will be at top dead center twice while the cams make one revolution. But with the timing cover off and you see that the marks are lined up properly, then there's no way that the cams can be out 180. That's what all the marks are for. There should be marks on the block to align the crank, also there are sometimes marks on the head for initial alignment of the cam sprockets, which are aligned with the cams themselves with dowel pins, and there are specific links on the timing chain(s) that are marked also. If all are aligned correctly, it's impossible to be 180 degrees off.

If things are not lining up according to the way the manual says they should, then there has to be something wrong somewhere. and of course, if you try to run the engine with the valve timing out of whack, at least on some engines, you will hit the top of the pistons with the valves and damage the engine.

The marks on the cam sprockets do not "match up with marks on the crank." The marks on both the crank and the cams match up with marks on the timing chain.

[BigNiner19]

Okay. by this post I assume you have a manual, and that's good to know. Surely your manual has some illustrations of correct alignment. My 150 manual shows the timing marks on the crank sprocket and the cam sprockets, along with the colored links on the cam drive chain(s), and how they need to be aligned in order for everything to be right.

Pardon me if I seem to state the obvious, but I have no way of knowing your level of knowledge. Valve timing is critical to your engine's operation.

Cams turn at half the speed of the crank, so the crank will be at top dead center twice while the cams make one revolution. But with the timing cover off and you see that the marks are lined up properly, then there's no way that the cams can be out 180. That's what all the marks are for. There should be marks on the block to align the crank, also there are sometimes marks on the head for initial alignment of the cam sprockets, which are aligned with the cams themselves with dowel pins, and there are specific links on the timing chain(s) that are marked also. If all are aligned correctly, it's impossible to be 180 degrees off.

If things are not lining up according to the way the manual says they should, then there has to be something wrong somewhere. and of course, if you try to run the engine with the valve timing out of whack, at least on some engines, you will hit the top of the pistons with the valves and damage the engine.

The marks on the cam sprockets do not "match up with marks on the crank." The marks on both the crank and the cams match up with marks on the timing chain.

Okay, so I can assume that if all marks line up correctly, then I am good to go. I wasn't sure if it were possible to line up all the marks but still have to adjust something else. I believe initially I only made one revolution to line up top dead center, so when I removed the head and placed them back as I removed them, I was putting them back 180* out thinking it was correct.

Yes, I have the manual. Hope to have this completed by this evening. Then put everything back together. The head gasket fix was the easiest part of this whole assembly.

[Harper]

Yeah, with the heads off, you can turn the crank all you want, and as long as it's back on TDC when you put it together, it doesn't matter how many times you turned the crank without the heads. Since the crank makes TDC twice with each cam revolution, it's the cams that determine whether you're TDC between the compression/power stroke or TDC between the exhaust/intake stroke. You're good to go.

[BigNiner19]

Just reporting back. Got everything lined up and timed correctly. The whole job, was time consuming but slowly following along with a manual and typical tools, the entire job can be completed. Engine hoist is a must.

[Harper]

Thanks....good to hear. Happy boating!