adding cubic inches effect on cam performance
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From: california
adding cubic inches effect on cam performance
going from a 95 ci to 103ci motor by changing to a 4 3/8 flywheel on my 2000 flht and was wondering what effect this would have on cam powerband if i use my same cams (S.E. 211's). I wanted to change to a different cam to have more low rpm power and less high end. I was told my 211's would now start sooner and end sooner by having the increased stroke and cubic inches. Is this true and if so does anyone know how much sooner the power will kick in and end ?
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You are on the right path, the cams will come in sooner on a larger displacement bike, with that said, it may or may not sign off sooner and you might wanna consider that added stroke might not like to be turned the same as your 95 did, I say put it together and see how it rides, cams are easy to change ,
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going from a 95 ci to 103ci motor by changing to a 4 3/8 flywheel on my 2000 flht and was wondering what effect this would have on cam powerband if i use my same cams (S.E. 211's). I wanted to change to a different cam to have more low rpm power and less high end. I was told my 211's would now start sooner and end sooner by having the increased stroke and cubic inches. Is this true and if so does anyone know how much sooner the power will kick in and end ?
Scott
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From: deland,florida
what the guys are trying to get to,is that with more CID,your compresion will go up with the same cumbustion chamber.
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From: san antonio
For instance, if the heads are the early SE Performance heads with 76cc chambers, the 211s work but increase the stroke from 4.00" to 4.375" and you will have way too much compression with the 211s. That's why the guys are focused on chamber volume.
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From: california
djl and everyone else, thanks for being patient with me , I did miss the point. My builder said the compression would be 10 to 1 which is the max i want for reliability . My heads are early S.E. performance heads #16952-99a but i do not know if they were decked when installed and in it appears the chamber volume should be 76cc . I based 10 to 1 on my 95 inch motor from the s.e. cataloge description that "bolt on compression ratio 10.1:1 for big bore twin cam (1550)". i was running flat top s.e. pistons . So now i know (thanks again djl) 10 to 1 with the same cams will increase the compression. How do i figure out what it will be and what is the formula then to select a proper cam to match?
I do know the builder is using weisco (?) pistons and a S.E. 4-3/8 stroker flywheel.
So now you have me wondering what he will have to do to acheive this number (10 to 1) running the 211's If that is even advisable. I was considering new cams to lower the powerband when he said that would happen by the increase in displacement. So........nothing was ever mentioned of doing any thing to the heads and reliability has been emphazised over and over.
WHAT SHOULD MY BUILDER BE DOING to acheive the 10 to 1 ratio ? Sorry to ask a loaded question like that but i really have no clue in how you figure out a compression ratio. I have a lot to learn to make an informed descision it seems!
I do know the builder is using weisco (?) pistons and a S.E. 4-3/8 stroker flywheel.
So now you have me wondering what he will have to do to acheive this number (10 to 1) running the 211's If that is even advisable. I was considering new cams to lower the powerband when he said that would happen by the increase in displacement. So........nothing was ever mentioned of doing any thing to the heads and reliability has been emphazised over and over.
WHAT SHOULD MY BUILDER BE DOING to acheive the 10 to 1 ratio ? Sorry to ask a loaded question like that but i really have no clue in how you figure out a compression ratio. I have a lot to learn to make an informed descision it seems!