Camchain Timing Marks
 

Hi Guys

I am into the manual CCT job on my FireStorm and am at the stage of checking the lining marks, I don't so much have a problem more confused.

I am working on the rear cylinder, when I line up the rear cam lobes so they are pointing up and in and observe the timing mark, the pattern seems pretty random?

RT
RT
F
F
F
RT
F
F
F
F
RT
RT
F
F
F
F
F
RT
F (*15) WTF? (etc etc)

I guess it doesn't matter so much for what I need to do a I will turn it to RT with everything pointing the right way and change the tensioner, but what does all this mean?

Ta
Rpb

No I think I am being silly here, the RT mark must very quickly follow the F. So if you think you are lined up and it on the F, then turn it very slightly and you will hit RT!

You did find the factory service manual on here, correct?

The cam sprockets are identical for the intakes, exhaust, front cylinders and rear cylinders. They have markings for all of the positions that they need to be set to, e.g. RI is the rear intake, FE is the front exhaust.

The only relevant marks on the flywheel are the FT and RT marks. These are (kind of obviously) 90 degrees apart. A smarter person than me may know what the other marks that follow the T marks are for, possibly spark timing at idle?.

Without wishing to teach you to suck eggs, it is also useful to know that the camshafts turn at half the speed of the crank so that it takes two crank revolutions for each cam revolution, which is needed as it is a four-stroke. This is why the manual tells you to set the crank timing and then check the cams are pointing in the right direction, and if not, give the crank one full revolution (which will move the cams by half a turn).

Something I have found with older camchain engines is that the timing marks won't ever line up perfectly due to a bit of wear in the chains and I assume the guides.

https://cimg4.ibsrv.net/gimg/www.sup...71e05439ac.jpg

https://cimg1.ibsrv.net/gimg/www.sup...af6df66fba.jpg