904 vs 937 lifter a 460 heads 8500 plus rpm

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Re: 904 vs 937 lifter a 460 heads 8500 plus rpm

Post  10.0 on October 17th 2016, 1:56 pm

Just seen a deal where a used A-460 block had been bored for roller cam bearings incorrectly and the cam timing was totally different from the front of the block to the back.
The block was purchased that way and was getting larger lifters, when they started checking lifter locations, they discovered it.
Ya can't assume anything.

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Re: 904 vs 937 lifter a 460 heads 8500 plus rpm

Post  Lem Evans on October 17th 2016, 7:00 pm

DaveMcLain wrote:
Lem Evans wrote:At any rate, the bigger the cam dia. the more advantageous the bigger wheel is.....slows the roller wheel speed.  

Yes but the smaller the base circle the greater difference the size of the wheel makes to the cam action.  A larger wheel makes the cam more "radical".  Seat timing and lift remain the same but duration increases.  It makes a surprisingly small difference on most cams though even if you change the diameter quite a bit.

As usual you are correct, master. That's the reason I order cams for the wheel diameter being used. This is the way Comp's program works...I'm using 1234 lobe number as an example.

1234R = ground for a BBF or 55mm core with .750" wheel.
1234RE = """"""""""""""""""""""""""""""""""" with ~.815" wheel
1234RG = """""""""""""""""""""""""""""""""" with .850" wheel
1234MG = 60mm with .850" wheel..........etc.

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Re: 904 vs 937 lifter a 460 heads 8500 plus rpm

Post  DaveMcLain on October 18th 2016, 10:16 am

Lem Evans wrote:
DaveMcLain wrote:
Lem Evans wrote:At any rate, the bigger the cam dia. the more advantageous the bigger wheel is.....slows the roller wheel speed.  

Yes but the smaller the base circle the greater difference the size of the wheel makes to the cam action.  A larger wheel makes the cam more "radical".  Seat timing and lift remain the same but duration increases.  It makes a surprisingly small difference on most cams though even if you change the diameter quite a bit.

As usual you are correct, master. That's the reason I order cams for the wheel diameter being used. This is the way Comp's program works...I'm using 1234 lobe number as an example.

1234R =   ground for a BBF or 55mm core with .750" wheel.
1234RE = """"""""""""""""""""""""""""""""""" with ~.815" wheel
1234RG = """"""""""""""""""""""""""""""""""  with .850" wheel  
1234MG = 60mm with .850" wheel..........etc.

It is a good idea that they(Competition Cams) do offer different designs but the amount of difference from even radical changes in the size of the wheel is very small I would assume that they just make the changes in software which alters the "master" to produce the same motion.  Here is an example showing a hydraulic roller lobe designed for a .900 base circle using a .700 roller wheel compared to the same lobe run with a .900 wheel.  The differences are there but they are not as big as most people would assume even when changing the wheel diameter .200!  I'm trying to learn about this stuff and it is a lot of fun to be able to compare such things and see what changes.  



The initial acceleration from the base circle happens sooner with the larger wheel but isn't significantly higher.  Then the negative acceleration at the top of the lobe is lower with the big wheel.  It is interesting how the maximum velocity is lower with the larger diameter wheel and how the greatest differences between the two are where the velocity is the highest on the lobe not where the acceleration is the highest.  



This is a simple comparison of the lift produced by each follower on the same lobe and it shows a maximum difference of about .009.

Thinking about this I can't see any advantage to making anything smaller, base circle or roller wheel, the bigger the better. I would think that most of this standardization on a .750 roller wheel for a solid roller came about from having to package a drop in roller lifter for a .842 diameter(Chevy) lifter bore long ago.

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Re: 904 vs 937 lifter a 460 heads 8500 plus rpm

Post  Scott Foxwell on October 21st 2016, 8:44 am

DaveMcLain wrote:
Lem Evans wrote:
DaveMcLain wrote:
Lem Evans wrote:At any rate, the bigger the cam dia. the more advantageous the bigger wheel is.....slows the roller wheel speed.  

Yes but the smaller the base circle the greater difference the size of the wheel makes to the cam action.  A larger wheel makes the cam more "radical".  Seat timing and lift remain the same but duration increases.  It makes a surprisingly small difference on most cams though even if you change the diameter quite a bit.

As usual you are correct, master. That's the reason I order cams for the wheel diameter being used. This is the way Comp's program works...I'm using 1234 lobe number as an example.

1234R =   ground for a BBF or 55mm core with .750" wheel.
1234RE = """"""""""""""""""""""""""""""""""" with ~.815" wheel
1234RG = """"""""""""""""""""""""""""""""""  with .850" wheel  
1234MG = 60mm with .850" wheel..........etc.

It is a good idea that they(Competition Cams) do offer different designs but the amount of difference from even radical changes in the size of the wheel is very small  I would assume that they just make the changes in software which alters the "master" to produce the same motion.  Here is an example showing a hydraulic roller lobe designed for a .900 base circle using a .700 roller wheel compared to the same lobe run with a .900 wheel.  The differences are there but they are not as big as most people would assume even when changing the wheel diameter .200!  I'm trying to learn about this stuff and it is a lot of fun to be able to compare such things and see what changes.  



The initial acceleration from the base circle happens sooner with the larger wheel but isn't significantly higher.  Then the negative acceleration at the top of the lobe is lower with the big wheel.  It is interesting how the maximum velocity is lower with the larger diameter wheel and how the greatest differences between the two are where the velocity is the highest on the lobe not where the acceleration is the highest.  



This is a simple comparison of the lift produced by each follower on the same lobe and it shows a maximum difference of about .009.

Thinking about this I can't see any advantage to making anything smaller, base circle or roller wheel, the bigger the better.  I would think that most of this standardization on a .750 roller wheel for a solid roller came about from having to package a drop in roller lifter for a .842 diameter(Chevy) lifter bore long ago.
Lifter bore dia. definitely limits the wheel size. One thing I understand is that the bigger the core and lobe, the more accurately it can be ground. You can also get more lobe lift with the bigger cores and run less rocker. Lof of guys go that direction. That's another whole debate; more lobe, less rocker, or less lobe, more rocker. Bigger cores are also physically stronger and have less deflection, especially with 5 bearing cores.
Regarding the difference of .009" lift; What's more important to look at is the area that creates under the curve, not necessarily the net lift result.

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