CAM Regrinds are back - ZR-1 Net Registry Forums

LGAFF · 03-25-2011

Got my regrinds back: Intake: Primary 222/415 lift Secondary 236/425 Exhaust 222/415 lift

Regrind is on bottom, stock cam on top

Rerind on Left

Regrind on left

LGAFF · 03-25-2011

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?

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 · 03-25-2011

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

LGAFF · 03-25-2011

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 · 03-25-2011

What is the difference in base circle?

LGAFF · 03-26-2011

Looks like its abouty a 1.-1.2mm difference

todesengel · 03-26-2011

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.

Locobob · 03-26-2011

Quote:

Originally Posted by LGAFF

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 · 03-26-2011

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

Coupe89 · 03-27-2011

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

03-25-2011	#1
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,194	CAM Regrinds are back Got my regrinds back: Intake: Primary 222/415 lift Secondary 236/425 Exhaust 222/415 lift Regrind is on bottom, stock cam on top Rerind on Left Regrind on left __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 Last edited by LGAFF; 03-25-2011 at 08:46 PM.

03-25-2011	#2
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,194	Re: CAM Regrinds are back 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? 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 __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 Last edited by LGAFF; 03-25-2011 at 09:24 PM.

03-25-2011	#3
sammy Join Date: Jun 2010 Location: back in lone pine Posts: 591	Re: CAM Regrinds are back maybe a dumb ? but do you still use the stk lifters or do you have to get a special set ?

03-25-2011	#4
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,194	Re: CAM Regrinds are back 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. __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

03-25-2011	#5
Locobob Join Date: Jan 2004 Location: Portland, OR Posts: 1,057	Re: CAM Regrinds are back What is the difference in base circle? __________________ Robert ZR-1 Net Registry Oregon State Director 91 ZR-1 #431 Black/Black LPE 368

03-26-2011	#6
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,194	Re: CAM Regrinds are back Looks like its abouty a 1.-1.2mm difference __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359

03-26-2011	#7
todesengel Join Date: Apr 2010 Location: O'Fallon, Mo Posts: 738	Re: CAM Regrinds are back 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.

03-26-2011	#9
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,376	Re: CAM Regrinds are back Doesn't the ramp angle also increase and require increased cam torque to rotate the camshaft? __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

03-27-2011	#10
Coupe89 Join Date: Aug 2009 Location: Livermore, Ca Posts: 203	Re: CAM Regrinds are back I'm wondering if I got this right. Do you need to install smaller cam bearing if you do this? __________________ 1990 ZR-1 #642