Camshaft sprocket setting after head planed

[lagonda 42]

My car is a late 1989 CTi 1.6. The head, and camshaft, were replaced by those from a 1.9, as the original 1.6 cam was (typically) worn, and the head was cracked. The head was planed just enough to ensure 100% flat, and because this brings the cam sprocket closer to the crank sprocket, the 10mm dowels for timing checking don't fully line up. Currently, with the crank 10mm dowel correctly engaged with the crank pully and timing recess, the dowel for the sprocket is roughly half its width from entering the hole in the block. I would need to turn the sprocket clockwise (ie normal rotation) to get the 10mm dowel to properly enter its timing hole. This presumably means the valve timing is slightly retarded. The only adjustment (no vernier pulley!) would be to jump the drive belt back one tooth, which would then mean the valve timing would be slightly advanced.

 

Which is preferable?!

[DamirGTI 342]

I did the "one tooth belt jump" and it works for really heavy head skim .. no valve/piston contact issue , starts , runs , idles good but the engine will be a little bit down on power from mid to high revs , however low down torque will increase - it's a little bit too much advance , one cam tooth is around 8.5 deg.if i remember .. usually you need around 4 deg. and not much more than that .

 

Cheap vernier option is fitting an 1.5 TU5D cam gear (it's adjustable , and fits on the XU engine/cam/head) , just needs some trimming on a lathe to make it thinner , but really easy to do .

 

 

D

[petert 589]

you can offset the dowel, or use an XU10J4RS pulley with a shim

[DamirGTI 342]

How to work out where to reposition the dowel on a std. pulley ? and does the original dowel hole needs filling up/welding ?

 

 

D

[lagonda 42]

Hi both,

 Many thanks for replies. I think Peter means the peg/protrusion on the sprocket itself, that engages with the keyway in the camshaft. Hadn't thought of that! Thanks particularly Damir re your experiences moving on a tooth ... better leaving it where it is than doing that!

Laurence

[DamirGTI 342]

Yes , the pin/keyway which locks onto the cam is removable on some OE pulleys  .. some are fixed some are pressed in/removable ... i have 3-4 OE pulleys with the pressed in pin/keyway , but the tricky bit is precise calculation where to reposition the pin so that the pulley is then advanced 4deg. .

 

If one tooth on outer pulley circumference makes it 8.5deg of advance (or retard) , then the lock pin/keyway on the centre of the pulley needs repositioning to a very small increments counting millimetres one or two me thinks ..

 

With an heavy head skim , +2mm taken off .. the cambelt will be dangerously loose and performance will suffer , you can squeeze manually the belt tensioner to pick up the slack from the belt but only up to a limit .. or jump a cam pulley one tooth to advance , the belt will be nice and tight as it should but as said one full tooth is a bit too much of cam advance , needs to be around half the tooth which will roughly be 4deg. (if the complete/full tooth is 8.5deg.) .

 

D

[Tom Fenton 1,542]

It is quite a simple job for anyone with a mill and a dividing head to pick up the original pin location and then index round and drill a new hole.

Personally I would probably index round 180 degrees plus/minus whatever offset was required, that puts your new dowel location well away from the original, and at the same time drill a new hole in another pulley web for a new locking pin to allow the initial timing to be easily set up.

 

[DamirGTI 342]

Rough representation , sorry ! , obviously needs careful measuring/drawing to make it spot on :

 

 

 

... but something like so , right Tom ?

 

D

 

[Tom Fenton 1,542]

Yes, but I doubt you could measure and draw accurately enough, hence needing a dividing head which will allow you to get it nigh on exact. Certainly +/- 0.5 deg. Counting the teeth on the photo there are 43 so you can't just do it at 180 degrees, but the principle is the same.

[petert 589]

Or drill out the existing hole with an 8mm milling  cutter, offset 4 degrees. Then turn up a new stepped pin and press it in the new hole. 

[DamirGTI 342]

That'll be job for my machinist then !

 

Anyways , i have TU5D pulley on mine .. seemed easiest/cheapest solution .

 

D