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#1
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No valve adjustment for 1998 Nissan DOHC 4-valve 2.4L?
Why does the owner's manual specify no valve adjustment interval even
though the lifters are solid rather than hydraulic? This engine has no rocker arms but has the cams press directly against the lifters and uses disks of various thicknesses to set the clearances. However Toyota has similar valve train designs but specifies a 60K adjustment interval for them. Does Nissan use harder valves and seats or something? |
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#2
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Toyota is being more conservative.
In practice, with normal oil changes, because the DOHC valve train is so short, and with four valves per cylinder, the valves are smaller and lighter, plus generally drenched in oil (valve actuators under the cam lobes) adjustement is generally not required. Have known of people checking them regularly up to 300,000 miles and still fine. |
#3
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Toyota is being more conservative.
In practice, with normal oil changes, because the DOHC valve train is so short, and with four valves per cylinder, the valves are smaller and lighter, plus generally drenched in oil (valve actuators under the cam lobes) adjustement is generally not required. Have known of people checking them regularly up to 300,000 miles and still fine. |
#4
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#5
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larry moe 'n curly wrote:
> Why does the owner's manual specify no valve adjustment interval even > though the lifters are solid rather than hydraulic? > > This engine has no rocker arms but has the cams press directly against > the lifters and uses disks of various thicknesses to set the > clearances. However Toyota has similar valve train designs but > specifies a 60K adjustment interval for them. > These types of valve trains almost never need any adjustment unless parts are wearing out. The -old- VW's that "needed adjustments" had a design flaw with the parts in the head and are the only engine of this type I've ever seen that had issues like that. -- Steve http://www.atlantaracing.com |
#6
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I've worked on Fiat engines that had pretty much the same configuration as
the one you describe. Once initially set, they never needed readjustment, as others have mentioned, unless you change something like grinding valves, replacing valves, etc. On one particular Fiat 128 that I worked on, the owner had just had a valve job done at a dealership in Houston. The car was running pretty poorly, and I found the valves badly burned. The 'dealership' mechanic had ground the valves but had just reassembled it... he never reset the clearances by using the disks, the valves went bad immediately, and the dealership wouldn't even respond to the owner. I re-did the work, set the clearances (in one case had to grind a bit off the end of the valvestem), and put it back together. The engine lasted until the car collapsed into a pile of rust, considerably later. So if you ever have to have valve work, be sure that the person who does it knows what it is all about. |
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