Cam timing problem - would like some assistance

[vince_aust]

Gents, hope someone can assist?

I am In the middle of engine reassembly after a top end rebuild. Completed cam timing of left bank as per Wayne's book - went to do right side and decided to replace chains and sprockets. Once completed - set valve timing on number 4 cylinder all ok. Rotated main pulley to check and found pulley jammed at approach to TDC .

At this point in the process Inlet valve 4 just starts to open (valve open maybe 40%) and then everything jams? I cannot rotate pulley anymore until I loosen valve swivel foot on number 4 inlet completely. Once I have loosened the valve gap on number 4 the pulley is free to turn and inlet valve number 4 opens completely?

This has got me stumped and would like some direction from the expertise on this forum.

Notes:

1. I assume I have the correct cams in each side as I managed to set timing ok on left side
2. I assume chain is on sprocket correctly as No1 and number 4 cylinders open 360 apart
3.if I have both chain tensioner under no tension the chain becomes tight on alternate rotations ??
4. I assume that valves are ok as once rocker arm gap loosed the valve is free to completely open
5. Heads, valves, springs etc have been professionally refurbished. There was very little skimming of the heads and everything went back together smoothly as per Wayne's book
6. Engine seems to rotate via pulley freely otherwise

[Daviboy]

Vince whilst not an expert they are going to ask questions like:
Type of motor? - 3.0 or 3.2L I assume 3.0 but should never assume
Type of cams?
Type of pistons?
How much was skimmed off the heads?
Did you use shims on heads and if so what size?
Did you check deck height prior to mounting cam towers?

I ask this because I had a similar issue during my 3.0 rebuild and it sounds to me like you have piston to valve clearance issues. Also when timing the right bank did you have the dot on the camshaft pointing down? To time the left bank the dot on the left cam needs to be facing up, when pulley at TDC, then put your depth gauge on the valve head and rotate 360° check valve movement depending on your cams etc. If not in spec loosen nut move pin and try again until resluts are consistent. I rechecked about 10 times before I called it good. Once happy tighten up 46mm nut and move to right bank. Turn the pulley until at BDC and the dot on the right cam is pointing down, then repeat previous process until happy. Hope this helps but I would check piston to valve clearance first and dont force the pulley or you will bend a valve stem. Reread the section in Waynes book as it is clear once understood on position of cams during timing.

[Flat6pac]

You need to pin both cams at the same time with the keyway in the 12 oclock position.
360 degrees set left pin for desired amount.
move dial guage to #4 and 360 degrees rotate to desired area and set to number.
when you changed chain wheel you must have lost something. Back crank back 30 to 40 degrees and move the cam where you need it then move crank back to center line. At that point you need keyway down at 6 oclock.
Bruce

[vince_aust]

Guys thanks for prompt replies - some answers as follows:

motor is 3.2. Nothing was skimmed of heads other than a lite skim to clean all up
Everything is standard (including cams), pistons were reused but new rings - top end rebuild was done to get over worn valve guides issue but motor had only done 90Miles. Head heights were checked prior to assembly and no shims were required.

Cam timing on right hand side was pointing down as per book instructions

Not sure how I can have a piston to valve clearance issue as valve will open fully up when I loosen valve timing lobe? It jams when valves open approx 40% but when I loosen valve lobe it opens all the way when I rotate past TDC (loosing valve clearance allows pulley rotation)

Both cams were set with keyways at 12 oclock position - if they were not could I achieve valve 1 and 4 opening @ 360degrees and 720 respectively???