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Crank build for racing engine
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<blockquote data-quote="greg brillus" data-source="post: 179193" data-attributes="member: 597"><p>Yes the titanium valves are fine until you machine them.......however, its not disastrous so long as you catch it and do something about it as we have done.......When you modify them and clean up the surface of the stem it looks perfect so you are hopeful that nothing will happen......but it appears to be very abrasive not only the stems but the seat faces as well.......Some would ask.......why bother......well its all about reducing the reciprocating mass so you don't have to run massive valve springs which then can become destructive.......These valves came from NASCAR engines running near 10,000 rpm all day long with massive springs........so us running them to say 7000 max with less springs should be fine.......so why the big spring pressures........Roller cams.......it is these and modern spring technology that has allowed a V8 to put out 3 times the power it use to.......With a follower ratio of 1.2 and rocker ratio of 1.25 0.400" lift at the cam gives 0.600" at the valve........This amount of lift and holding it there much longer than a flat tappet cam is what gives you more power........and also reducing the massive duration normally used on high performance engines.......the sooner you close that inlet valve, then the compression builds much better.......big duration cams cause the inlet to close very late......Some about 70 or even 60 degrees before TDC.......this is why their power band is up high in the rev range.........We want massive torque out of the corners........Testing so far has given us just that......After more run time it will be interesting to see what the pin looks like........Often difficult to fully center the rods on a twin.......if the bore mouths are not right or the spacer between the rods is the same........They were never designed as a performance engine.......just a big lazy twin to ride for miles.</p></blockquote><p></p>
[QUOTE="greg brillus, post: 179193, member: 597"] Yes the titanium valves are fine until you machine them.......however, its not disastrous so long as you catch it and do something about it as we have done.......When you modify them and clean up the surface of the stem it looks perfect so you are hopeful that nothing will happen......but it appears to be very abrasive not only the stems but the seat faces as well.......Some would ask.......why bother......well its all about reducing the reciprocating mass so you don't have to run massive valve springs which then can become destructive.......These valves came from NASCAR engines running near 10,000 rpm all day long with massive springs........so us running them to say 7000 max with less springs should be fine.......so why the big spring pressures........Roller cams.......it is these and modern spring technology that has allowed a V8 to put out 3 times the power it use to.......With a follower ratio of 1.2 and rocker ratio of 1.25 0.400" lift at the cam gives 0.600" at the valve........This amount of lift and holding it there much longer than a flat tappet cam is what gives you more power........and also reducing the massive duration normally used on high performance engines.......the sooner you close that inlet valve, then the compression builds much better.......big duration cams cause the inlet to close very late......Some about 70 or even 60 degrees before TDC.......this is why their power band is up high in the rev range.........We want massive torque out of the corners........Testing so far has given us just that......After more run time it will be interesting to see what the pin looks like........Often difficult to fully center the rods on a twin.......if the bore mouths are not right or the spacer between the rods is the same........They were never designed as a performance engine.......just a big lazy twin to ride for miles. [/QUOTE]
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Crank build for racing engine
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