Re: Cams
[Re: racerx]
#1578826
02/14/14 12:56 PM
02/14/14 12:56 PM
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Joined: Jan 2003
Posts: 9,996
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
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master
Joined: Jan 2003
Posts: 9,996
Frostbitefalls MN (Rocky&Bullw...
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The lobe lift is limited to about .515 or so, and the next thing is cam core flex, which limits the rate of lift along with limited lobe profiles. Duration isn't limited, so you can go way too far with that. I don't know just how much the cam core flex and twist affects the motor, but I am sure it is quite measurable. The gen III Hemi has a very large cam core to allow high rates of lift with limited duration, and may also be bigger to offset cam twist. This brings up the question, best answered by cam engineers, of how much different installed centerline the bigger cam cores need to address cam twist in the older cam core size. If it is significant, then there is the answer. That would be compensation for cam twist.
Last edited by gregsdart; 02/14/14 01:22 PM.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Cams
[Re: racerx]
#1578827
02/14/14 01:11 PM
02/14/14 01:11 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I'm running a .640/.640 lift in my 416 in the Rampage its not the limit by far EDIT with 1.5 ratio rockers 
Last edited by MR_P_BODY; 02/14/14 01:26 PM.
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Re: Cams
[Re: pittsburghracer]
#1578834
02/14/14 02:28 PM
02/14/14 02:28 PM
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Joined: Oct 2011
Posts: 515
geezer acres rest home
dakotawilly
mopar
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mopar
Joined: Oct 2011
Posts: 515
geezer acres rest home
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810/775 for me,with 1.7 rockers,that translates into 476/455 actual lobe lift.but I know there are others running higher actual lobe lift,i have no idea what the max limit is,or the amount of twist and flex,i guess some of that would be determined by cam core quality and hardness.i am sure some cam companys test this and require at least a specific core hardness,also as lift increases,so should the base circle,but I am sure theres a point of no return here,without the proper supporting equipment for extreme lifts,head flow,cubic inches,geometry,etc,you will just be wizzing in the wind,matched combination makes power.in my years I have seen way too many over cammed combinations,killing power and torque,i believe the largest cam listed in the bullet catalogue is 510 lobe lift,thats 867 w/1.7 rockers........I would like to know the outcome of this myself.......... 
Last edited by dakotawilly; 02/14/14 02:45 PM.
SFI 25.5 depends,no leak,even at 213 mph....
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Re: Cams
[Re: dakotawilly]
#1578835
02/14/14 02:51 PM
02/14/14 02:51 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
810/775 for me,with 1.7 rockers,that translates into 476/455 actual lobe lift.but I know there are others running higher actual lobe lift,i have no idea what the max limit is,or the amount of twist and flex,i guess some of that would be determined by cam core quality and hardness.i am sure some cam companys test this and require at least a specific core hardness,also as lift increases,so should the base circle,but I am sure theres a point of no return here,without the proper supporting equipment for extreme lifts,head flow,cubic inches,geometry,etc,you will just be wizzing in the wind,matched combination makes power.in my years I have seen way too many over cammed combinations,killing power and torque,i believe the largest cam listed in the bullet catalogue is 510 lobe lift,thats 867 w/1.7 rockers........I would like to know the outcome of this myself..........
How would the base increase if the lift increases...
the limiting factor on lift is the came tunnel..
(you cant get the cam in the tunnel if the lobes were
to start out larger than the tunnel) then they grind
from there... more lift they cut more out of the base
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Re: Cams
[Re: MR_P_BODY]
#1578836
02/14/14 03:01 PM
02/14/14 03:01 PM
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Joined: Oct 2011
Posts: 515
geezer acres rest home
dakotawilly
mopar
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mopar
Joined: Oct 2011
Posts: 515
geezer acres rest home
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to a point yes,you are correct,but the smaller the base circle,the more viscious lift and control at rpm becomes,ramp design,you can increase the base circle some,but not a huge amount for sure.once again theres a point of no return..its give and take for sure.......
Last edited by dakotawilly; 02/14/14 03:36 PM.
SFI 25.5 depends,no leak,even at 213 mph....
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Re: Cams
[Re: dakotawilly]
#1578837
02/15/14 01:53 AM
02/15/14 01:53 AM
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Joined: Aug 2008
Posts: 4,068
Mo.
racerx
OP
master
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OP
master
Joined: Aug 2008
Posts: 4,068
Mo.
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Quote:
810/775 for me,with 1.7 rockers,that translates into 476/455 actual lobe lift.but I know there are others running higher actual lobe lift,i have no idea what the max limit is,or the amount of twist and flex,i guess some of that would be determined by cam core quality and hardness.i am sure some cam companys test this and require at least a specific core hardness,also as lift increases,so should the base circle,but I am sure theres a point of no return here,without the proper supporting equipment for extreme lifts,head flow,cubic inches,geometry,etc,you will just be wizzing in the wind,matched combination makes power.in my years I have seen way too many over cammed combinations,killing power and torque,i believe the largest cam listed in the bullet catalogue is 510 lobe lift,thats 867 w/1.7 rockers........I would like to know the outcome of this myself..........
Hmm....so is all this with a stock block?
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Re: Cams
[Re: gregsdart]
#1578838
02/15/14 02:06 AM
02/15/14 02:06 AM
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Joined: Aug 2008
Posts: 4,068
Mo.
racerx
OP
master
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OP
master
Joined: Aug 2008
Posts: 4,068
Mo.
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Quote:
Yep, just cam lift. That is where BBC motors have a slight edge, they come with 1.7 ratio rockers stock. We are stuck with 1.5, which adds to the total weight the springs need to control .
So help me understand this,you're saying that an 1.5 is heavier than a 1.7?I know that the 1.7 adds to the lift.
One reason i bring this cam ? up is that generaly GM blocks seems to run much bigger cams than crylers.Do they use a bigger bearing jounal than us crysler guys to help support the cam flex?
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Re: Cams
[Re: racerx]
#1578839
02/15/14 02:15 AM
02/15/14 02:15 AM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Quote:
Yep, just cam lift. That is where BBC motors have a slight edge, they come with 1.7 ratio rockers stock. We are stuck with 1.5, which adds to the total weight the springs need to control .
So help me understand this,you're saying that an 1.5 is heavier than a 1.7?I know that the 1.7 adds to the lift.
One reason i bring this cam ? up is that generaly GM blocks seems to run much bigger cams than crylers.Do they use a bigger bearing jounal than us crysler guys to help support the cam flex?
I dont know about the journal size but stock they
run a bigger ratio rocker so they dont have to have
the base ground down smaller which helps with rigidity
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Re: Cams
[Re: racerx]
#1578840
02/15/14 03:03 AM
02/15/14 03:03 AM
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Joined: Jan 2003
Posts: 9,996
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
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master
Joined: Jan 2003
Posts: 9,996
Frostbitefalls MN (Rocky&Bullw...
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Quote:
Quote:
Yep, just cam lift. That is where BBC motors have a slight edge, they come with 1.7 ratio rockers stock. We are stuck with 1.5, which adds to the total weight the springs need to control .
So help me understand this,you're saying that an 1.5 is heavier than a 1.7?I know that the 1.7 adds to the lift.
One reason i bring this cam ? up is that generaly GM blocks seems to run much bigger cams than crylers.Do they use a bigger bearing jounal than us crysler guys to help support the cam flex?
The higher the rocker ratio, the less movement of the rockers and pushrods for a certain lift, which makes it easier on the springs. As Iunderstand it Mopar lifters are bigger, which allows a bigger roller wheel, which helps a touch for rate of lift.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Cams
[Re: racerx]
#1578842
02/15/14 03:28 PM
02/15/14 03:28 PM
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Joined: Oct 2011
Posts: 515
geezer acres rest home
dakotawilly
mopar
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mopar
Joined: Oct 2011
Posts: 515
geezer acres rest home
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i am sure there is something to that,pro stock guys are well over an inch of lift ,but,they use a cam bearing for every pair of lobes,9 to be exact,,and their cam bearings I believe are 70-75 mm,HUGE,by any standards.where and when the actual flex comes into play would vary by combination of valve springs,rocker ratio,rpm,and such.us "normal" racers aren't looking for every ounce of horsepower at any cost either.i guess the best scenario would always be run what the manufacturer recommends and forget it.their history and r&d wouldn't lead you astray for sure,their reputation depends on it...........
Last edited by dakotawilly; 02/15/14 03:36 PM.
SFI 25.5 depends,no leak,even at 213 mph....
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whats the biggest cam have someone has use in a stock block?And i no it's has alot to do with combos,did not what to get into that,just what to hear what size have uall used in a stock block i did not what to hi-jack the other thread with this ? so thought i'll start a new one............Tha 
