Hey folks,
Now that I've adjusted the valves on my 3RZ-FE (in a 1999 4Runner) over a period of 60,000 miles I wanted to share some interesting trends. In the table below you'll see the data I have gathered for each adjustment. The "lash before" is what was measured before adjusting and "lash after" is after changing the shims (copy-pasted when no adjustment is made). The values in yellow indicate that I changed a shim. (FYI this engine uses the shim over bucket design)
What you'll notice is that the exhaust valves always tend to tighten and seem to do so at a rate of about 0.5 thou per 20,000 miles. The intake valves generally tighten a bit but not nearly as fast.
My conclusion is that once you know your current lash values, and if they are near the center of the spec, you should be able to get away with checking them every 40k at the most. Also, this suggests that it always makes sense to adjust the valves to the high side of the spec since they tighten over time -- this is in line with general good practices anyway.
Maybe not specifically applicable to most folks but figured the analytical types here might enjoy some data.
Now that I've adjusted the valves on my 3RZ-FE (in a 1999 4Runner) over a period of 60,000 miles I wanted to share some interesting trends. In the table below you'll see the data I have gathered for each adjustment. The "lash before" is what was measured before adjusting and "lash after" is after changing the shims (copy-pasted when no adjustment is made). The values in yellow indicate that I changed a shim. (FYI this engine uses the shim over bucket design)
What you'll notice is that the exhaust valves always tend to tighten and seem to do so at a rate of about 0.5 thou per 20,000 miles. The intake valves generally tighten a bit but not nearly as fast.
My conclusion is that once you know your current lash values, and if they are near the center of the spec, you should be able to get away with checking them every 40k at the most. Also, this suggests that it always makes sense to adjust the valves to the high side of the spec since they tighten over time -- this is in line with general good practices anyway.
Maybe not specifically applicable to most folks but figured the analytical types here might enjoy some data.
