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, Tue, 26 Apr 2005 16:13:13
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"Rock" means the exhaust valve is just starting to close and the intake valve is just starting to open. As you turn the engine, you'll see the exhaust valve go down, then start to come up, just as the intake valve starts to go down. As the exhaust continues to go up and the intake go down, they'll reach a point where they're level with each other. That's the "rocking" point. I think it's called "rocking" because if you were to turn the engine slightly in both directions (which you shouldn't do!) they'd appear to rock back and forth.
The rocking valves are NOT the ones to adjust -- instead, when one set of valves is rocking, it means that the camshaft is completely clear of another set, and THESE are the ones you should adjust. You do it this way so the valve clearance isn't influenced by pressure from the camshaft -- the pushrods are all the way down and the valves are all the way closed, so the rocker arms have some clearance against the valve stems (which is what you're setting.) Obviously, once the cam lobes start pushing on the pushrods and the pushrods press the rocker arms onto the valves, this will close up any clearance and you won't be able to measure or adjust it.
How I do it: I put the car in 4th gear (making sure the freewheel is locked) and jack up one front wheel, leaving the other wheel on the ground. I turn the engine by turning the raised front wheel in the forward direction -- it gives you plenty of leverage and makes it easy to turn the engine slowly so you can see the "rocking" position come up easily on each set of valves.
You probably have a chart like this in your manual, but here it is anyway:
Rocker arms rock at cylinder #4 -- adjust valves on cylinder #1
Rock at #2 -- adjust #3
Rock at #1 -- adjust #4
Rock at #3 -- adjust #2
How you adjust 'em: When you've got the valves of the target cylinder in the neutral position (per the chart) you make sure the inner end of the rocker arm is pressed down against the pushrod, then slide a flat feeler gauge in between the other end of the rocker arm and the stem of the valve. You're aiming for a "drag fit" -- the gap should be tight enough that you feel a slight resistance as you slide the blade of the feeler gauge through it, but not so tight that you have to use a lot of force to make it move. I don't know if this will make sense to you or not, but I think of it as about the amount of drag you feel when you're writing with a lead pencil -- a definite resistance, but smooth.
If the gap is too wide (no resistance as you push in the feeler gauge) then you make it smaller by tightening down the adjuster on the other end of the rocker arm -- this pushes down more on the pushrod and closes up the gap. You don't have to turn it far -- half a flat (1/12 turn) makes a noticeable difference! If the gap is too tight (lots of resistance, or you can't get the feeler gauge in at all) then you widen it by screwing out the adjuster -- this makes more room between the rocker arm and pushrod, and lets the rocker arm rise off the valve stem a bit more.
Oh, yeah, and you set the clearances with the engine cold: 0.014 inch for the intakes and 0.016 inch for the exhausts. Again, this is bound to be in your manual, but I thought I'd mention it so all the info is in one place.
So, is that all you can stand to know about adjusting valve clearances? Well, you should be all set -- go to it! Have fun...
posted by 68.227.170...
, Tue, 26 Apr 2005 16:13:13, Wed, 27 Apr 2005 06:07:29
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