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MG MGB Technical - Setting Valve Clearances

Can anybody find fault with this method of setting the valve clearances? It seems much, much simpler than the various rules of seven, nine, etc.

Turn the engine until it is at TDC on cylinders 1 and 4 - when the timing marks are aligned. Take off the distributor cap, the rotor arm is pointing to the cylinder just about to fire ie at the top of the compression stroke so both valves will be well and truly closed. Set the clearances on this cylinder. Wind the engine through 180 degrees clockwise (you can mark the front pulley opposite to the normal timing mark to make sure you get it right) and set the clearances on the cylinder next in the firing sequence (1,3,4,2). Then turn the engine another 180 degrees so that the timing marks line up and do the next one, and another 180 degress to do the next one.

Neil
Neil Lock

Hi Neil

This is known as setting the tappets on the rock.When the piston at TDC has the valves rocking (one opening the other closing) set the tappets on the other TDC piston. The rule of nine seems easier to me and I mark each rocker as I adjust it.

Peter
peter burgess

I think I'm using the rule of 9, but

I turn the engine until a valve is fully open, then

If it is the second valve from the front that is down, I adjust the second valve from the back, 4th from front down, adjust 4th from back and so on.

I keep turning the engine and watching the valves, until I get back to the first one I adjusted = 2 full turns to do them all.

I don't need to look at anything except the valves, the timing marks are not required.
Martin Layton

I knew what I was doing works, it just seemed easier to understand. Then again, I do have the radiator out and so it is really easy to turn the engine with a big socket on the front pulley nut...

Neil
Neil Lock

I do it Martin's way. It's also convenient since with the plugs in the engine will stop only at positions with two valves almost fully open, and the corresponding "closed" valves acceptably closed and on the base circle. The following comment on cams applies with this variant as well. Neil's method usually will work, but drastic cams can cause trouble, since long duration may result in the "closed" valves being on opening/closing ramps.
Be aware that both Martin's method and the rule of nine that derives from it do not work on non mirror engines, like some Fords, with valves arranged IE, IE, IE, IE
FRM
FR Millmore

Pick any cylinder, turn the crankshaft in the normal direction. Adjust the exhaust valve just as the intake closes, adjust the intake just as the exhaust starts to open.
John H

I adjust my valves "on the rock"
I put the car in 4th gear and roll it to get the valves to rock.
Quick, easy, and accurate.

Rich
Rich McKIe

I find my back few valves can't be set accurately with the 'rule of nine' as the clearance is still changing when its partner valve is fully down. I still use the rule (again much easier than looking at timing marks) and nudging the car along in 4th but test either side of the strict 'rule of nine' point looking for the point of greatest clearance before setting the gap. It's only a few degrees, but it certainly makes setting easier. I say 'setting', but in fact since I started doing this I haven't had to alter the gaps in years, whereas before I couldn't get repeatable gaps from one turn of the engine to the next.
Paul Hunt 2

I take the coil HT lead off and nudge with the starter(I'm lazy)
K Harris

Engine not car!!
K Harris

This thread was discussed between 23/03/2007 and 25/03/2007

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