Hughes Reground Cam

[bbeep71]

Hi Guys,
Can someone explain how a cam can be re-ground and lift is now greater than what it was? Also when you use a reground cam do you need to use special pushrods or etc. to obtain the lift.
Thanks
bbeep71

[amxauto-x]

When you regind, you can grind it to a smaller base circle and leave the "top" of the lobe close to the same. And so have a greater lift.

The length of the rods doesn't have anything to do with the lift., but will take up the difference in the diameter of the smaller base circle. Or you can use adjustable rockers if you are using hydrolic lifters.

[bbeep71]

Hi amxauto,
I guess I don't understand the concept of smaller base circle. If the cam is still located in the cam bearings at the same center axis of the cam, how does a smaller base circle help. I guess I find it hard to understand how lobe lift increases when the distance from center of cam to height of lobe remains the same. Hopefully you can explain this and thanks for your patience.
bbeep71

[amxauto-x]

I can't make a drawing on here and I'm not all that good at using words. I'm better at showing then telling. The base circle is where the cam is round/partly round where the lifter is setting on when the valves are closed. The 1/2 of the cam that is round then goes up into the lobe. Imagine that being completly round and no lobe. That is the base circle. When it is reground that circle is now smaller. The top of the lobe is barely gound again and so is not shortened. Say you have a circle of 1 inch. and the lobe sticks up 1 inch above that, like a mountain above a plain. If you grind the circle 1/2 inch smaller [dia.] but grind the top of the lobe .020. then the dif is .480. so in affect you've increased the lift by .240 [1/2 the dia]

[6 packin]

When looking at any camshaft the lobes are concentric, you have a heel and toe of a camshaft. Whent the engine turns and the lifter rides on the heel there is no lifting on the push rod. Untill it starts the ramp of the toe. Too measure a camshaft for lift simply measure the toe or fat part of the cam with a nice set of calipers. Then turn it around and measure both the heel and toe of the lobe, subtract the 2 and it will give you the ramp or lobe lift. Times that by your rocker ratio (factory is around 1.5) and will tell you lift. So if you grind down the heel part of the cam, given the same amount on the toe (changing the ramp), you can see how that would effect it.

[bbeep71]

Hi amxauto and 6 packin,
Thank you for your explanation. I guess I was confused because I was using the center of the cam as a reference. I now realize that the key here is to use the base circle in relationship to the lobe height. I now understand. You did a great job in explaining it. Thanks for your time and patience in solving this little mystery. I try to understand how it works and then sometimes I get in trouble. I'm building a 88 318 with roller cam for my 66 cuda and I will have Hughes regrind this cam.
bbeep71

[bbeckwith]

Hey amxauto-x,

I was waitin for you to use the ol licorice example heh heh. jk, remember when I asked about torsion bars? LOL

Bruce

[amxauto-x]

Ya, I member that now. Hey ifin it works

[bwlizard]

AMXauto-x, That was an excellent explaination ! Even I understood that !

[amxauto-x]

I understand "simple" I'm VERY simple!

[rumblefish360]

And people laff at me when I explain things in this mannor. But then again, when I'm done, they understand. The KISS method is best, even more so here where drawing and refrance books are not so easy to show,
K - keep
I - it
S - simple
S - stupid
Or stupid simple.

[amxauto-x]

that's me--simple--and stupid