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I am attempting to set the valve clearance on a 356. The engine has just been rebuilt by Porsche but has very noisy tappets. What I find strange is that some of the pushrods can be pushed back into the casing against the cam then spring back out about 5mm as if there is a spring between the cam and followers. So once clearances are set to 0.006" and 0.004" as per normal I can then push hard on the pushrod end of rocker and it moves a further 4-5mm then springs back out.
Old 02-17-2018, 08:05 AM
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Crank position set to TDC when you make the adjustment?
Old 02-23-2018, 05:09 AM
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Yes. But even if it wasn`t that wouldn`t account for how I can press the pushrods and followers against the cam and they spring back.
Old 02-24-2018, 07:48 AM
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Did you figure out what is happening here? With what and how hard are you pushing the pushrod against the cam follower? I suppose if you pushed hard enough you could flex/bend the pushrod, but to get 4-5mm of movement I don't think it would spring back.
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Old 02-27-2018, 01:53 PM
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I`m only pushing the pushrod with the palm of one hand then it springs back. The engine is being stripped to find out why next week.
Old 02-28-2018, 02:41 PM
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It`s sorted. Taking the bottom cover from engine it was immediately obvious what it was. The Porsche specialists (muppets) who built the engine have bent 3 of the pushrod tubes inside the crankcase . One was so bad that it was pushing the pushrod sideways so when the valve is closed it wasn`t seating fully in the cam follower. When the cam starts to open the valve the valve spring pressure is enough to fully seat the pushrod into the follower slightly bending the tube out of the way. You can see the witness marks on the inside of the tube just in one place. So the pushrod in question would spring back out because the tube was pushing it out of the concave hole in the follower.
Old 03-02-2018, 11:29 AM
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Glad you found the problem. Will you have a go with the collapsible push rod tubes? Since you simply wanted to adjust the valves and not get into removing the heads, that seems a reasonable approach.
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Old 03-03-2018, 05:56 AM
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Glad you found the problem. Will you have a go with the collapsible push rod tubes? Since you simply wanted to adjust the valves and not get into removing the heads, that seems a reasonable approach.
I had to strip the engine to change the followers as three of them were damaged with the pushrods sliding sideways in and out of the follower sockets.
Old 03-09-2018, 10:42 AM
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..."engine rebuilt by Porsche"... would you tell us a little more what that means?
Old 04-09-2018, 07:06 PM
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Interested here as well.
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Old 04-30-2018, 07:02 PM
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