I got to comparing my new Crane 300H to the old Andrews B and the "B " should have a higher lift, but it is measuring less than the 300H ,could it be that worn or am I measuring it wrong. I believe the "B" should be .507 and the 300H should be .479, I'm getting close to the .479 for the 300 H , but I'm only getting .410 from the "B" , can it be that worn ? both intakes lobes are reading about the same.
My OEM cam in my other Pan had one intake lobe almost round .
Cams
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fourthgear
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FlatHeadSix
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Panacea
What? Does the push rod stretch when it goes up? Does the rocker "cam" when it rotates? What part of the valve train geometry accelerates the lift when it operates? I always thought it was pretty much a 1 to 1 ratio through all the moving parts. The only geometry affect would be in the hydraulic lifter systems, and they would usually decrease the lift.
just curious.....
mike
What? Does the push rod stretch when it goes up? Does the rocker "cam" when it rotates? What part of the valve train geometry accelerates the lift when it operates? I always thought it was pretty much a 1 to 1 ratio through all the moving parts. The only geometry affect would be in the hydraulic lifter systems, and they would usually decrease the lift.
just curious.....
mike
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mbskeam
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its called base circle of the cam,
what this means is the round part of the B cam has a smaller OD than the
300 H
measure the cam lift
measure the base circle then divide by 2 then subtract this number from the total lift, then times it by 1.5 (rocker arm ratio) this should be your lift....
clear as mud
mbskeam
what this means is the round part of the B cam has a smaller OD than the
300 H
measure the cam lift
measure the base circle then divide by 2 then subtract this number from the total lift, then times it by 1.5 (rocker arm ratio) this should be your lift....
clear as mud
mbskeam
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FlatHeadSix
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thanks guys, it makes perfect sense now. I forgot about the unequal arm length. Panacea's arm length measurements and mbskeams's 1.5:1 ratio explain the whole thing.
In my defense, most of my experience is with the flatheads, whatever lift the cam gives you is exactly what you get at the valve. (minus the valve lash at the tappet of course)
John, the teeter-totter analogy is very descriptive, you can prove it to yourself with a pencil and a ruler and moving the balance point. The end of the longer arm definitely travels further. Guess what I was doing at work today after you posted that? The guy in the cubicle across from me must have been watching me experiment with my "model" rocker arm and asked what I was doing. Now he's convinced that I'm totally nuts.
mike
In my defense, most of my experience is with the flatheads, whatever lift the cam gives you is exactly what you get at the valve. (minus the valve lash at the tappet of course)
John, the teeter-totter analogy is very descriptive, you can prove it to yourself with a pencil and a ruler and moving the balance point. The end of the longer arm definitely travels further. Guess what I was doing at work today after you posted that? The guy in the cubicle across from me must have been watching me experiment with my "model" rocker arm and asked what I was doing. Now he's convinced that I'm totally nuts.
mike
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fourthgear
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FlatHeadSix
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mbskeam
for lobe lift you subtract the entire diameter of the base circle from the total height of the cam to get the amount of lift from just the cam, then multiply by the rocker ratio to get valve lift. from the Lunati folks:
Understanding Camshaft Specifications
LIFT
Lift refers to maximum valve lift. This is how much the valve is "lifted" off its seat at the cam lobe’s highest point.
How is it measured?
Valve Lift is the amount (usually in inches) that the valve is lifted off of its seat. It is usually measured with a dial indicator at the tip of the valve. Lobe Lift is the amount (usually in inches) that the cam lobe increases in radius above the cam base circle.
Tip: To quickly find maximum lobe lift, measure the base circle of the cam and subtract it from the thickness across the cam lobe’s highest point (see the diagram below).
Tip: Maximum valve lift can be calculated by multiplying the maximum lobe lift times the rocker ratio. For example, a 0.310" lobe lift cam yields 0.496" of valve lift when using a 1.6 ratio rocker arm.
Formula: valve lift = lobe lift x rocker ratio
for lobe lift you subtract the entire diameter of the base circle from the total height of the cam to get the amount of lift from just the cam, then multiply by the rocker ratio to get valve lift. from the Lunati folks:
Understanding Camshaft Specifications
LIFT
Lift refers to maximum valve lift. This is how much the valve is "lifted" off its seat at the cam lobe’s highest point.
How is it measured?
Valve Lift is the amount (usually in inches) that the valve is lifted off of its seat. It is usually measured with a dial indicator at the tip of the valve. Lobe Lift is the amount (usually in inches) that the cam lobe increases in radius above the cam base circle.
Tip: To quickly find maximum lobe lift, measure the base circle of the cam and subtract it from the thickness across the cam lobe’s highest point (see the diagram below).
Tip: Maximum valve lift can be calculated by multiplying the maximum lobe lift times the rocker ratio. For example, a 0.310" lobe lift cam yields 0.496" of valve lift when using a 1.6 ratio rocker arm.
Formula: valve lift = lobe lift x rocker ratio
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fourthgear
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mbskeam
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well...
I am wrong sorry, I had to go back and look at my book,I just remembered that the cam heel dia was split in 2 in the illustration I have. subtract the full dia not 1/2 like I said...
but the smaller base/heel dia is how you get higher lifts in the same space as smaller lift cams.
my bad.....
mbskeam
I am wrong sorry, I had to go back and look at my book,I just remembered that the cam heel dia was split in 2 in the illustration I have. subtract the full dia not 1/2 like I said...
but the smaller base/heel dia is how you get higher lifts in the same space as smaller lift cams.
my bad.....
mbskeam