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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
hard valve seats
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<blockquote data-quote="oexing" data-source="post: 119709" data-attributes="member: 1493"><p>Heat expansion variations of 11 or 13 just account to minimally different sizes of rings I guess, not really relevant when looking at 0,20 mm shrink . Your tool steel was heat treated for use at 550 degrees, don´t think it will change dimensions in the engine. Plus the seat ring will not get much above 300 degrees in an alu head with great heat conduction.</p><p> My choice of 1. 2379 was from using it in the toolroom : At 12 % chrome it is a pig to machine, more so for reaming numerous bores as is typical in mould fabrication. It blunts reamers in short tiime - meaning it is very high wearing - or should I say low wearing ?? Confusing in English . A seat ring does not really need high hardness, some engine types got alu bronce rings or sort of cast iron types traditionally. While lead was used in fuels the lead prevented micro wear on the iron rings but today you need a different approach: That is why I went for the high chrome types and they don´t need to be 60 HRC as you want to machine the ring after dropping it in the head, so used in "soft" state. The chrome will provide a mini coat of well wearing protection so no lead is no problem. Of course you pick good valves as well with powder welded seat section. Don´t know about valves from the Spares Co so got mine from the motor trade like TRW , diesel valves my choice as sort of nimonic material, lightened.</p><p> I do not believe a ring will change its dimension by heat in use, this would have been known for many decades . When it really drops out it has more to do with uncorrect shrink fit and no substantional dimensions of ring or alu head recesses, not because of dimension changes from heat effects.</p><p> When having done heavy machining on components it is certainly a good idea to put them on an electric cooking plate at a few hundred degrees for a while to get stress lelieving before finishing to shrink sizes.</p><p> Did you look up my Ebay link, many seat rings easy for sale and correct material I´d think . Getting types from big companies may be awkward for small orders. Today I´d take that route , cheap enough and not a big operation on the lathe like with 2379 bars. "Hardened" seat rings is not quite correct, they have to be machineable , it is just a matter of wear resistance.</p><p></p><p> Vic</p></blockquote><p></p>
[QUOTE="oexing, post: 119709, member: 1493"] Heat expansion variations of 11 or 13 just account to minimally different sizes of rings I guess, not really relevant when looking at 0,20 mm shrink . Your tool steel was heat treated for use at 550 degrees, don´t think it will change dimensions in the engine. Plus the seat ring will not get much above 300 degrees in an alu head with great heat conduction. My choice of 1. 2379 was from using it in the toolroom : At 12 % chrome it is a pig to machine, more so for reaming numerous bores as is typical in mould fabrication. It blunts reamers in short tiime - meaning it is very high wearing - or should I say low wearing ?? Confusing in English . A seat ring does not really need high hardness, some engine types got alu bronce rings or sort of cast iron types traditionally. While lead was used in fuels the lead prevented micro wear on the iron rings but today you need a different approach: That is why I went for the high chrome types and they don´t need to be 60 HRC as you want to machine the ring after dropping it in the head, so used in "soft" state. The chrome will provide a mini coat of well wearing protection so no lead is no problem. Of course you pick good valves as well with powder welded seat section. Don´t know about valves from the Spares Co so got mine from the motor trade like TRW , diesel valves my choice as sort of nimonic material, lightened. I do not believe a ring will change its dimension by heat in use, this would have been known for many decades . When it really drops out it has more to do with uncorrect shrink fit and no substantional dimensions of ring or alu head recesses, not because of dimension changes from heat effects. When having done heavy machining on components it is certainly a good idea to put them on an electric cooking plate at a few hundred degrees for a while to get stress lelieving before finishing to shrink sizes. Did you look up my Ebay link, many seat rings easy for sale and correct material I´d think . Getting types from big companies may be awkward for small orders. Today I´d take that route , cheap enough and not a big operation on the lathe like with 2379 bars. "Hardened" seat rings is not quite correct, they have to be machineable , it is just a matter of wear resistance. Vic [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
hard valve seats
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