CAM Regrinds are back

[LGAFF]

Got my regrinds back: Intake: Primary 222/415 lift Secondary 236/425 Exhaust 222/415 lift
http://i134.photobucket.com/albums/q115/lgaff/166.jpg

Regrind is on bottom, stock cam on top

http://i134.photobucket.com/albums/q115/lgaff/165.jpg
Rerind on Left

http://i134.photobucket.com/albums/q115/lgaff/164-1.jpg

Regrind on left

[LGAFF]

To many people the process of regrinding a camshaft is a black art, resulting in the inevitable
question :
?How can you machine metal away from a cam, yet have it finish up with more duration and lift??
It works like this?

http://i134.photobucket.com/albums/q115/lgaff/Untitled-2.jpg
In (Fig. 83), the outer contour represents the
original lobe shape and the cam lift is represented
as dimension ?A?, the difference between the base
circle radius and the nose.
The duration of the lift is shown as 120 degrees at
the cam, which would be 240 degrees at the
crankshaft, because the camshaft rotates at half
crank speed.
The inner contour line shows the cam shape after it
has been reground and it can be clearly seen that
the lift has now been increased to the dimension
?B?, this time the difference between the new basic circle radius and the nose.
At the same time the duration has been increased to 160 degrees at the cam, that is 320 degrees at
the camshaft.
From this diagram it is also now possible to see why the cast iron cam lends itself so readily

[sammy]

maybe a dumb ? but do you still use the stk lifters or do you have to get a special set ?

[LGAFF]

I will need to check cams/lifters to see if they will work, as my heads have had 2 valve jobs, OEM lifters were alittle tall, this may solve that problem.

[Locobob]

What is the difference in base circle? :happy1:

[LGAFF]

Looks like its abouty a 1.-1.2mm difference

[todesengel]

Looks like you are getting everything in just in time for a late spring/early summer install. Will be interested to see how it all works out for ya. :thumbsup:

[Locobob]

Looks like its abouty a 1.-1.2mm difference

Is that diameter or radius?

I think I recall someone (probably Pete) saying that our lifters had about .06in worth of preload (room).

1-1.2mm = .04-.047in

If this is diameter then there should be no problem as the lifter would only have to make up for .02-.0235in
If it's radius then it still should be okay although seating the valves slightly deeper would provide a little extra comfort.

[A26B]

Doesn't the ramp angle also increase and require increased cam torque to rotate the camshaft?

[Coupe89]

I'm wondering if I got this right.
Do you need to install smaller cam bearing if you do this?

[XfireZ51]

What works for me is to think of it as the ratio between base circle height v lobe height. If the base circle represents where the valve is closed, then the valve begins opening sooner, open longer and deeper with the regrind. The center of the base circle is moved closer towards the tip of the lobe. Having just had a larger intake installed, I can tell you it changes the bass note of the idle. You won't be balancing a nickel on the plenum anytime soon.

[VetteMed]

I'm wondering if I got this right.
Do you need to install smaller cam bearing if you do this?

The bearing surfaces are not reground - only the lobes.

[LGAFF]

At Pete's today, we confirmed that the regrind, which is about .025 to .030 ground off the stock cam, will allow me to use the new stock OEM replacement lifters, despite the valves being set in from 2 valve jobs. If Phil lets me, I will write an article on checking the lifter height to ensure that the cams do not hang the valves open.

[A26B]

Let you write an article???? I'm sure he would be very happy to have your contribution. I know you'll put some photos in there too!

[Locobob]

At Pete's today, we confirmed that the regrind, which is about .025 to .030 ground off the stock cam, will allow me to use the new stock OEM replacement lifters, despite the valves being set in from 2 valve jobs. If Phil lets me, I will write an article on checking the lifter height to ensure that the cams do not hang the valves open.

So we have an effective height difference of .025 to .030 to be absorbed by the lifter preload then?

[LGAFF]

Correct!

[Locobob]

Correct!

Well that doesn't seem bad at all if the lifter does indeed have .060 of play like I have heard.