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PV, 120 (Amazon), 1800 General Forum for the Volvo PV, 120 and 1800 cars |
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hardened valve seats.Views : 609 Replies : 2Users Viewing This Thread : |
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Mar 1st, 2016, 13:40 | #1 |
arcturus
Last Online: Yesterday 07:14
Join Date: Mar 2006
Location: Sagres Portugal
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hardened valve seats.
Just out of interest, what's the deal with hardened valve seats. Are the seats bought separately, from a specialist or does the machine shop source and fit them. How are they fitted in?
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Mar 1st, 2016, 13:51 | #2 |
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Location: essex
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The machine shop has them, or sources them, they are an interference fit, by cooling the seats right down they shrink enough to fit in position.
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Mar 2nd, 2016, 03:35 | #3 |
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Last Online: Aug 29th, 2016 19:28
Join Date: Oct 2013
Location: Seattle
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Back in the olden days when petrol had lead, the deposits would cushion the hammering of the valves. Thanks to clean air laws, lead was eliminated back in the 1970s. Without the lead cushion, the extreme heat and the constant pounding would basically crush the cast iron valve seats especially the exhaust ports.
The solution is to have a machinist cut out the old seats and press in new ones made of hardened steel. I just had this done. Some will say that valve seat recession is a myth but I assure you it is not! Mine were so bad that the #4 cylinder could no longer hold pressure. |
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