Cams

Posted By: racerx

Cams - 02/14/14 12:46 PM

I'v seen seen the tread on here bout "Help me pick a cam for my 511"and had me thinking

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

P.S i filled out the cam questionear with Bullet cam and they recommendation the they gave me were pretty close to what i have

Posted By: gregsdart

Re: Cams - 02/14/14 04:56 PM

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.

Posted By: MR_P_BODY

Re: Cams - 02/14/14 05:11 PM

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

Posted By: Dodgeguy101

Re: Cams - 02/14/14 05:17 PM

I am assuming they are talking before the ratio of the rocker arm adding in there. Not total lift, just at the cam.

Posted By: gregsdart

Re: Cams - 02/14/14 05:25 PM

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 .

Posted By: pittsburghracer

Re: Cams - 02/14/14 05:51 PM

Back in the 70's and early 80's the R286 cam (750 lift) was VERY popular. Most of use ran them on .030 over 440 engine with TRW pistons, stock rods, and stock cranks. My Duster ran a 9.81 with one and I still have 3 of them sitting on a shelf.

Posted By: Jeremiah

Re: Cams - 02/14/14 05:55 PM

How high did you guys spin those .030 440's? Do you know the duration @.050?

Sincerely,

GIT (gearhead in training)

Posted By: Biginchmopar

Re: Cams - 02/14/14 05:59 PM

The biggest cam I have run is .475" lobe 308*@0.050"

I believe cam size is duration not lift but to each their own.

Posted By: pittsburghracer

Re: Cams - 02/14/14 06:03 PM

Quote:

How high did you guys spin those .030 440's? Do you know the duration @.050?

Sincerely,

GIT (gearhead in training)

The 286 is at .050 and pretty sure 332 total rings a bell. I ran a 14-31 Goodyear slick with 4.56 gears shifting at 6800. Direct Connection rod bolts, shot peened rods, with polished beems.

Posted By: dakotawilly

Re: Cams - 02/14/14 06:28 PM

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..........

Posted By: MR_P_BODY

Re: Cams - 02/14/14 06:51 PM

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

Posted By: dakotawilly

Re: Cams - 02/14/14 07:01 PM

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.......

Posted By: racerx

Re: Cams - 02/15/14 05:53 AM

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?

Posted By: racerx

Re: Cams - 02/15/14 06:06 AM

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?

Posted By: MR_P_BODY

Re: Cams - 02/15/14 06:15 AM

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

Posted By: gregsdart

Re: Cams - 02/15/14 07:03 AM

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.

Posted By: racerx

Re: Cams - 02/15/14 03:40 PM

Okay i see,so both brands have there advantages to a degree Hummm...Thaxs fellas

Posted By: dakotawilly

Re: Cams - 02/15/14 07:28 PM

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...........

Posted By: jafr

Re: Cams - 02/17/14 02:08 AM

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?

If you are referring to a big block Chevy, there is a big difference in port volume and shape as compared to a big block Wedge headed Chrysler. You could run a cam grind designed for a Chevy but it would not perform as well as a grind designed for a Chrysler.

A big Chrysler has a factory .904 lifter which is larger than a Big Chevy. Having the bigger lifter lets you have a faster ramp speed on the camshaft without destroying the cam lobe or the lifter. Most aftermarket Chevy blocks come with a .904 lifter bore.