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by foshi
< Vitesse — Coolant Escaping When Hot Valvetrain noise looking for my old car > | ||||||
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![]() posts: 531 non member |
posted Fri 16th Oct 2020
Hi. If a valve clearance is too large, what metal part on metal part is making the excess noise, or is it a few things please?. Thanks for any replies. Dave |
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Tags - Vitesse | ||||||
![]() posts: 1479 non member |
posted Fri 16th Oct 2020
reply 1 of 5
well the rocker arm hitting the stem will always generate a noise but the bigger the gap the faster the arm is travelling so producing a louder noise. To prevent any noise there needs to be no gap but then there would be no room for thermal expansion or valve settling and risk valves not closing completely.... |
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Tags - Vitesse | ||||||
![]() posts: 531 non member |
posted Sun 18th Oct 2020
reply 2 of 5
Thanks Glang. I always assumed that's what made the chatter, though if I have a hose to ear and top of valves I don't think I hear much, so was wondering?. There normally isn't any separation between cam lobes/tappets/pushrods/rocker adjuster screws when running to make any noise, I assume?. Dave |
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Tags - Vitesse | ||||||
![]() posts: 1479 non member |
posted Sun 18th Oct 2020
reply 3 of 5
Correct, no other gaps, which I assume is achieved just by gravity as I cant think of any springs or other means..... |
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Tags - Vitesse | ||||||
![]() posts: 2285 Spitfire & GT6 Model Consultant Cambridge group joined on Sun 11th Apr 1993 |
posted Sun 18th Oct 2020
reply 4 of 5
I don't think it's purely gravity. The pushrod has a cup one end and a dome that fits in the follower at the other. Both of these are shapes that attract an oil film and hold by surface tension or suction. So the easy places for a gap to develop are the rocker to valve and the follower to cam. Given that the valve spring has pushed the mechanism back, inertia will encourage the follower to rest against the cam and the rocker to separate from the valve.
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Tags - Vitesse | ||||||
![]() posts: 1479 non member |
posted Sun 18th Oct 2020
reply 5 of 5
Yes it makes you wonder how it works on upside down or radial engines in aircraft.... Also wouldnt it be better to have the gap between the cam and followers (effectively like a OHC) as theres more surface area in contact so less wear rate? |
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Tags - Vitesse | ||||||
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