Author Topic: '71 A65L valve timing  (Read 306 times)

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Caulky

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'71 A65L valve timing
« on: 21 April, 2018, 15:39:10 »
Sorry to bring this up, again.
Now, have I got this right?
I have read all that I could find on this subject, but some things are still confusing.
When doing this job, some say the 'clock' should be on the valve collar or on the rocker arm adjuster.
Others say, this is incorrect because the quoted figures are for the pushrods/tappet followers.

Another thing is, people talk about 'lift', do it at .040".
Lift meaning valve lash? It could mean, turn the crank + .040" @ 0.015" lash, after the needle begins to move and read the degree-wheel?
Also, taking the WSM figures for inlet: open 51* BTDC, close 68* ABDC at 0.015" lash.
Using these figures, we have 51+180+68 = 299*. 299/2 = 149.5*.
The cam lobe centre is given as 98.5* crank ATDC, so for the cam centre we subtract 51* from 149.5* = 98.5, OK fine. (this MAY be the lobe peak, but not neccessarily).
But, the quietening cam ramp needs to be avoided, so the measurements need to taken at .040" lash, not at 0.015"
OK so far?

AWJDThumper

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Re: '71 A65L valve timing
« Reply #1 on: 21 April, 2018, 16:19:15 »
If the valve opening and closing times are specified at 0.015" gap then that is what the tappet clearance must be set at. What you then need to sense is when the valve starts to open or just starts to close. The most accurate way is to put a dial gauge on the valve stem or collet - you can't sense valve opening/closing by putting the gauge on the rocker arm or adjuster.

The purpose of the 0.015" specified gap is that it takes into account the quietening ramps on the cams. Simply measure the opening and closing angles with that gap set and then compare with the specified values. The position of the centre of the cam is neither here nor there!

JulianS

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Re: '71 A65L valve timing
« Reply #2 on: 21 April, 2018, 16:26:53 »
The 15 thou needs to be set when the cam is on its base circle, that is in the normal position for tappet setting - set inlet when other inlet is fully open.

AWJDThumper

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Re: '71 A65L valve timing
« Reply #3 on: 21 April, 2018, 22:17:48 »
If you don't have a dial gauge, you can use a 2 thou feeler gauge to sense when the gap is just about to close just before the valve is about to open, or just after the valve has closed and the gap is just about to open out. Not as accurate as using a dial gauge but probably accurate enough to confirm the valve timing is more or less what its supposed to be.

Caulky

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Re: '71 A65L valve timing
« Reply #4 on: 17 May, 2018, 18:05:39 »
Hi again
After changing to the drive-side inlet valve only, and by advancing the cam-wheel by one tooth, the opening time on the degree wheel was reasonable.
So, fit the other inlet valve...but check the closing time first.
Same trouble, too early! 45 degrees after ABDC.
It makes me think I have the wrong camshaft fitted?
The other problems are mounting the clock and setting the tappet gap.
To eliminate the gap trouble, I clocked the adjuster screw to .015", by lifting/dropping the rocker arm.
The clock is reasonably steady, but as the rocker-arm moves, so does the angle.
As far as I can tell, the lobe centre is good.
I'm not happy with this, but what to do? Getting hacked-off with this.
Even if the inlet side is OK, the exhaust is likely to be wrong.

AWJDThumper

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Re: '71 A65L valve timing
« Reply #5 on: 17 May, 2018, 19:44:48 »
Is this engine mounted in the frame or still on the bench? It sounds as though you need some help in measuring the valve timing. Where are you based?

Caulky

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Re: '71 A65L valve timing
« Reply #6 on: 17 May, 2018, 20:08:41 »
The engine is in the frame.
I'm on the Isle of Wight.