OE Exhaust Valves, Sodium |
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OE Exhaust Valves, Sodium |
914werke |
Apr 1 2006, 10:04 PM
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#61
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"I got blisters on me fingers" Group: Members Posts: 10,138 Joined: 22-March 03 From: USofA Member No.: 453 Region Association: Pacific Northwest |
I know Jake suggests tossing these, but unfortunantly Im rebuilding a set of heads. Id like to keep them stock, but Im more concerned about longevity.
Is there anything that can be done to improve thier function? Cryo? (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif) |
davep |
Apr 3 2006, 02:06 PM
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#62
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914 Historian Group: Benefactors Posts: 5,152 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada |
Yes, the main problem is with worn guides. For efficient heat transfer you need metal to metal contact with only enough oil to prevent seizing and to fill all the voids. As the guide wears, there is less contact, more oil and sometimes air bubbles. Neither air nor oil conducts heat like metal so the heat transfer goes down and the valve stem temperature goes up. Once guide wear begins the process accelerates. While guide wear is a big problem it is not the only problem. The state of engine tune and valve adjustment can also play a significant part. So does the amount of cooling air the engine gets. More modern guide materials help a lot, but are not a godsend. To paraphrase Jake, it is all in the combo. |
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