Saturday, Apr 14, 2012 at 20:25
G'day marc p
You seem unfamiliar with engine valve train designs. They don't have two methods of adjustments, only one.
The term "tappet adjustment is a term used by many but it isn't accurate and doesn't indicate the reality of the situation.
Traditionally tappets are at the end of a rocker arm and the cam the other end. Cam can be in the middle on some makes.
The valve is opened by the ratio of cam to pivot to valve, hope this makes sense to you.
With a bucket, sometimes the shim is between the bucket and valve stem and others have the shim in a recess in the top of the bucket. The cam presses on the bucket/shim and directly pushes the valve open.
Cam profile and lift size is quite different for each type of arrangement.
Some engines have a screw adjustments for the valve clearances and others with a, bucket/cam have a shim adjustment.
Many toyotas have the shim adjustments as do lots of other brands.
The cam to bucket clearance has to be measured so a shim of the correct thickness can be calculated when the actual shim is removed and also measured.
Sometimes a thicker one is required and sometimes a thinner one.
Most people draw up a chart of all the valve clearances as they are in the beginning and then remove all the shims from the engine and keep them in order.
When the shims are measured, the appropriate thicknesses are used in the correct positions and only some have to be purchased to get the remaining valve clearances correct.
If people go to a motor wreckers they can buy shims from dead engines of other Toyota models and use them to suit the clearances which need shims.
Ross M
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