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General Minitrail Talk
Tech Area
Verify Oil Pump Flow - Top End Noise
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<blockquote data-quote="69ST" data-source="post: 185947" data-attributes="member: 5"><p>Unlikely as plug-to-piston contact seems to me, this is a very good point to raise...and so easy to check.</p><p></p><p>For a short-run test, the valve clearances can be set really tight. You'd never want to run with overly tight valve lash but, for a few seconds up to a couple of minutes, you could set the valves a tight as they will go while still allowing the engine to run. If the noise vanishes, or decreases, you'll at least know that it's related to the rocker arms. No difference and you'll know to look elsewhere. Do this testing with one rocker at a time. The objective is to isolate the source.</p><p></p><p>Addendum...</p><p>I've run across pistons that were noisy...and very difficult to pin them down as the source. There was a batch of aftermarket pistons that rattled like hell unless installed backward...with the sparkplug relief on the wrong side(!). That was a good 5-6 years ago, seems unlikely any of those pistons would still be sold as of this late date. Another possibility is piston-to-head, or piston-to-valve, contact. If the tolerances are just on the jagged edge, thermal expansion would account for the timing (IOW when the noise occurs) without bending/breaking something. I'd not pull the head until such time that the valvetrain has been ruled-out as the source.</p></blockquote><p></p>
[QUOTE="69ST, post: 185947, member: 5"] Unlikely as plug-to-piston contact seems to me, this is a very good point to raise...and so easy to check. For a short-run test, the valve clearances can be set really tight. You'd never want to run with overly tight valve lash but, for a few seconds up to a couple of minutes, you could set the valves a tight as they will go while still allowing the engine to run. If the noise vanishes, or decreases, you'll at least know that it's related to the rocker arms. No difference and you'll know to look elsewhere. Do this testing with one rocker at a time. The objective is to isolate the source. Addendum... I've run across pistons that were noisy...and very difficult to pin them down as the source. There was a batch of aftermarket pistons that rattled like hell unless installed backward...with the sparkplug relief on the wrong side(!). That was a good 5-6 years ago, seems unlikely any of those pistons would still be sold as of this late date. Another possibility is piston-to-head, or piston-to-valve, contact. If the tolerances are just on the jagged edge, thermal expansion would account for the timing (IOW when the noise occurs) without bending/breaking something. I'd not pull the head until such time that the valvetrain has been ruled-out as the source. [/QUOTE]
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Verify Oil Pump Flow - Top End Noise
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