Cam timing - vertical or parallel?

[c21vhpd]

Johnty helped me do my cam timing last weekend, and a few days later, his tuition has sunk in and I think I get it! One question remains though. We set the lift at TDC by arranging the dial gauge to travel parallel with the motion of the follower, which makes sense as that is the lift of the valve. But there is some intrinsic inaccuracy in getting the angle right, plus it proved impossible to mount the gauge rigidly enough to ensure an accurate reading.

 

Then I noticed on Julian's V11UFO cam cover pages that he has arranged for a vertical dial gauge clamp directly above the follower - which is a jolly smart idea - a nice rigid mount in exactly the right place. So is he just expecting that whoever is using this arrangement to compensate for the fact that the gauge is moving vertically, or is the 'lift at TDC' in fact quoted for vertical travel rather than parallel, since it's easier to accurately arrange the gauge vertically than perfectly parallel to the follower?

 

Honda Passion Orange, 640kg , and proud of it

[John Howe]

Assuming you are talking K series... take a piece of say 2" steel bar and bolt it to the top of the head...

 

You now have a fixing point for the magentic base to your dial gauge. Since the gauge has umpteen angle variations, simply set it to as close as parallel to the travel of the followers and then take you measurements from the top of the followers.

 

Any variations to parallel will not have a major effect on your timing measurements and the movement of your followers only reflects on the cams and therefore your valve travel.

 

If you need a length of steel bar to mount from, just shout as we have the odd tonne that we are trying to find a home for.

[oilyhands]

This can easily be arranged using a small mounting bracket that bolts to one of the cam cover bolt holes, such a bracket should hold the gauge at 22 degrees to the vertical, this is the follower angle, the probe of the dial gauge can be cranked around the cam so as to rest on the follower face, it will then accurately reflect the follower movement in the same plane. Even with a vertically mounted gauge, basic trigonometry will show that the reading is pretty accurate.

 

I have a bracket for the inlet follower and another for the exhaust, plus one for a third dial gauge to accurately measure TDC, if you would like a photo of the three dial gauges and brackets, let me know.

 

Oily

[Johnty Lyons]

This is in effect what we did using a steel plate bolted to the cam cover bolt hole and using a piece of welding wire to extend the dial guage probe with a bend round the cam. It has always worked so far and I have no reson to doubt it now. However my plate holds the magnetic base in a vertical plane and the 22Deg angle is accomplished by the angle arms on the mount I can see no benefit in an angled base ??? I can however see the benifits of using a three guage setup as per DW But havent had the resource or the finance to invest in this yet

 

jj

N.I. L7C AO.

Membership No.3927.

[c21vhpd]

Thanks all - it seemed perfectly logical to measure the lift in the direction of travel - it was only Julian's vertical clamping arrangement that made me wonder as to how lift at TDC was defined.

 

Honda Passion Orange, 640kg , and proud of it