"....No argument with comments however Rosebud question still is " how to accurately establish fully open valve" Alex infers close is good enough ( I agree) but dial indicator would provide best accuracy...."

Best accuracy for what???  You're only interested that the valve being measured is closed... and this is indicated by the corresponding valve being "more or less" open.  How open, as long as its "mostly" is totally irrelevant....  Rosebud is only asking about "how open" due to misunderstanding about how the system works..

".....For anything but a full-race engine where you are setting the tappet gaps individually to chase every tenth of a horsepower, this is more than adequate...."

And it seems its important to point out that while Alex talks about individual gaps being relevant on a race engine, he's talking about the size of the gap......not how its measured...

Cheers, Ian 

+1
By 'proper sequence' I observe which valve opens next in sequence and use the rule of 9 to determine which valve to adjust. (uses a lot less driveway!)

Not bothering to jack it up, I pushed my car across the driveway in 4th gear, stopping every foot (or less) to adjust each valve in proper sequence

Agreed

For anything but a full-race engine where you are setting the tappet gaps individually to chase every tenth of a horsepower, this is more than adequate.

 

Think about it, even a 320° full race cam has the follower sat on the base circle for over half the time...

No argument with comments however Rosebud question still is " how to accurately establish fully open valve" Alex infers close is good enough ( I agree) but dial indicator would provide best accuracy.

+1 to Alex's comments.  

It's actually a very easy and very effective way of performing the task.  The rule of 9 isn't complicated.

When a valve is fully closed, the cam follower is on the base circle which generates the maximum free play in the valve train - the tappet gap.  A few degrees either side of this isn't going to make any difference as the cam follower is on the base circle for a long time.

To establish when the follower is on the base circle, you observe the other valves to determine when theey are fully open - a much easier thing to do.

With the engine stone cold, wind it round until one of the valves is fully open.  Count which valve it is (you ought to count right to left, but it doesn't really matter as long as you stick to the same side) and subtract that from nine.  If No 6 valve is down (inlet on 3) then you adjust valve number 3 (inlet on No2), if 4 is down you adjust 5, and so on.

It isn't difficult.

I tend to put the car in gear and roll it forward from the passenger side by rotating the front wheel while watching across the valves for movement.  With practice, it can be done start to finish in 10-15 minutes.

The rule of 9 is just an efficient way of running through the process.

While the valve is only fully open for a relatively short time it is fully closed for at least 1/2 the cam rotation (basic geometry will demonstrate this).  And you're setting the gap with the valve closed...

So don't sweat it. If 1 "looks like" its at full lift then 8 is measurable....

Cheers, Ian

We used the screwdriver method to find TDC on 2 stroke MCs back in the 60's. Worked great. But setting valve lash on a 4 stroke I suspect is another matter. Just wish I could tell with certainty when the cam follower is completely [CORRECTION] on the lobe.

Quote:
I would guess that it is a progression such that turning the engine is minimized. i.e. when #1 valve is set then a slight engine rotation will bring up #3 etc. 

Actually, Haynes' method requires a lot of engine cranking to get through all 8 valves. So, I think there's something else at work here.

Sorry didn't read Haynes before posting.
I just do it the practical way which is good for all engines. BMC recipe is specific to those 4 cyl engines with that valve arrangement. I would guess that it is a progression such that turning the engine is minimized. i.e. when #1 valve is set then a slight engine rotation will bring up #3 etc etc. The best way i know to show valve is fully open is to put a dial indicator on the rocker arm and set it at max indication. If i were following that i would still just look at the piston and find where it changes direction. Some put a screwdriver on the piston for a better visual of piston changing direction. A few mm either side should not affect gap setting.

I'm following Haynes; "adjust valve no. 1 when valve no. 8 is fully open, etc.," so I'm looking for fully [CORRECTION] open valves. Yeah, adjusting a valve w/ the piston @ TDC seems simple enough, but since Haynes recommends this rather complicated procedure (rule of 9's), I figure it must be for good reason. Perhaps the valves aren't fully closed at TDC on the compression stroke due to cam overlap?

Unless I'm reading wrong you need to set the valve gap when fully closed not when open. When cylinder is on compression stroke you can see top of piston with spark plug out. set valve to rocker gap to spec .012?. Valve fully open is just a function of cam lift and doesn't get "set".

Is there an accurate method to determine when a valve is completely open for valve adjustment purposes? I'm currently rocking the car w/ the trans in gear and eyeballing the rocker arm until a given valve appears to be fully open. Turning the engine over by hand doesn't seem to be any better. Seems to me if +/- a couple thousandths of an inch is the difference between a burnt valve and worn pushrods, these methods leave a lot to be desired. Any thoughts?