Setting Valve timing with unmarked sprockets

[Phil C]

Morning All

Fitting new cam chain and sprockets (unmarked).

Is it possible to turn the cam and crank independently without introducing the valves to the pistons?

I can’t remember if an open valve protrudes beyond the head face.

I am looking to reconfirm TDC using a piston stop and thought I should remove the rocker shaft first just in case?

thanks

 

[DJB350Z]

What engine is this - Aren't all 6 cylinder Triumph engines non-interference?

[Phil C]

2 litre Vitesse. 

[Wagger]

It will be non interference unless you have had monster amounts of machining off the cylinder head, and fitted a high lift cam. A piston stop will create solid interference, so disconnect the battery before using it. I have never used one. Just shone a light down a plug hole, rotated forward, back and repeated until satisfied. Always finish this by rotating in the engine direction of rotation. There are dial indicators that will fit in a plug hole, but you can break bits off inside the cylinder easily. Mark the pulley with white paint when sure it is at TDC.

I cannot remember now, but the Keyways should be in the positions shown in the workshop manual. I came unstuck with these as BMC engine keyways point at one another when it is correct. Not so on Dolomite 1500. They had to be 'Vertical', not quite facing one another. I'll try to find a drawing.

[Wagger]

Normally, there should be timing marks on both sprockets. A line scribed on each. If there are none the procedure in the workshop manual is (Slightly abbreviated):-

Rotate camshaft until number 12 pushrod is at is highest point. Adjust number 1 rocker to a 1mm gap in this position.

Repeat the procedure with number 11 pushrod at its highest point and adjust number 2 rocker to the same as number 1 rocker at that point.

Turn the crankshaft to bring nmbers 1 and 6 pistons to TDC. Fit the sprockets and chain in that setting.

 

The camshaft sprocket has two positions and can be reversed to achieve exact timing. Therefore giving four options.

It is tedious and I have never had to do this as I have always had timing marks on the sprockets.

Good luck.

 

[Phil C]

Thanks guys for the confirmation re interference.

I have a standard cam and the head has been lightly skimmed once so I guess all will be ok 🤞

the procedure seems straightforward enough if not a little tedious. Not something I’ve done before but always fun to learn new stuff!

[DanMi]

I found that when I did my cam, there is a good few degrees of movement just on the bolt holes so I check using 2 dial gauges such that with no1 at TDC both number 4 valves(4 cyl) have identical lift

[Wagger]

In 'Factory Standard Form' these engines are very tolerant of Valve and Ignition timing. When they are tuned, this becomes more of an issue. The really 'Fussy' tuner would check every cylinder, mke notes and then set all for the best compromise.

As the timing chain stretches, the tensioner actually retards the cam slightly. On an OHC engine, so does machining the head. This is often overlooked.

[Phil C]

I have restored the engine to standard spec so these finer points, whilst valid for achieving peak performance, will not be so important for me. All very interesting though!