Timing issue.

[Cushing]

Pulled my engine out again to fix the oil leak and noticed that when I turn the crank to TDC on the front pulley, the dots on the cams don't line up 100% and the TDC mark on the flywheel is off as well, why ? 

 

What's the best mark to use, rear flywheel or front pulley ? it's difficult to see the piston move with a screwdriver though the No 1 spark plug hole as well.

[giorgio67]

Mark on the flywheel is more precise, even if they must be the same, your sprockets are out of allignement of about half a teeth, if your engine was running well leave it as it is, you are within an acceptable error.

[MrDangerUS]

On the picture, both cams are slightly retarded (less than 1 tooth).

 

Culprit: short cam-to crank distance, which may be caused by by decking the block, skimming the head, skimming and re-machining the main bearing bore, skimming the cam carriers or use of a thinner head gasket.

What color dot cam pulleys are installed on your engine?

Edited July 10, 2015 by MrDangerUS

[sanj]

If he turns the crank so that the front timing mark lines up the cam pulley teeth will also move closer together.

[Cushing]

The photo of the pulley shows the crank lined up to TDC or 0, the black mark has been made by me when I turned the crank to get the cam marks lined up, it's not the TDC mark.

 

I have had the head skimmed and all sprockets are green dot. 

[Barrykearley]

There's something in the service notes about skimming, the amount you can skim off and if I remember correctly something about thicker gaskets????

[Vulcan Grey]

The rear timing mark is most accurate, the front timing mark is least accurate...

The cam marks don't actually appear to line up perfectly, usually...

But having skimmed the head, there is a possibility that the cam timing is slightly retarded. However, the later spec head gasket replaced the earlier gasket, and it is ~.020" thicker IIRC. Since the machining limit for skimming the head is lower than that, then you really should NOT have much retardation.

If you were out one whole tooth on the cams, that equates to 18deg, so it would be unlikely you are that far out!

The photo of the rear timing mark makes it look like you were not at TDC. Could be the angle though?

[Cushing]

Thanks Travis,  I did use the slightly thicker gasket as I skimmed the head. The pictures I posted are taken with the crank pulley set at TDC, so you see the cams are slightly off but not much, however, it's the flywheel mark that I'm more worried about, the picture  angle is bad but it's definitely off the TDC line.  

[Vulcan Grey]

Ignore the front crank marking. Just use the rear flywheel marking. Then check the cams, make sure they aren't off one tooth.

[Mr_John111]

Agreed, ignore front pulley. The woodruff key can open up the slot if the pulley bolt is loose and so it can flap about a bit.

My 2 cents