Cam wear

[rb77413]

Ok not a What cam do I need post. But I hope this hasn't been posted before. Last night pulled the intake to change gaskets, and while I was there I measured the lobe lift of the cam. According to manufactuers specs, it seems both intake and exhaust lobes wore .08-.09 inches. Valve lift should be I= .478 / E= .502, lobe was measured at .314 intake (.472 @ valve.) and .329 exhaust ( .493 @ valve) Is this normal wear for cam lobes. The rockers are isky 1.5. Haven't measured at valve, since I am going to be pulling the heads off in about a month anyways. Just seeing if I need to plan a cam swap along with the heads. Do all this at once. Thanks

[dwc43]

You did not say, but if this is a hydraulic cam then you are measuring it wrong. With the stock lifters they bleed down with no oil pressure. You need to use a solid lifter installed to check it at the valves. That's why your readings are off. If you did not check the lift when it was new on the lobe then that number means nothing to you cause ou have no reference to match it too.

[rb77413]

It is hydraulic, I dont have a solid lifter so thats why I measured it on the lobe. I just multiplied it by 1.5 to get the valve lift. True I have no basline. Just didnt seem right for it to be that far of from the advertised lift.

[dwc43]

Advertised lift includes the 1.5 ratio added to it so that's why it's off so much not to mention your depressing the lifter and even if it was full of oil it still has a predetermined amount of preload designed into it.

[rb77413]

When I measured the cam, I put the dial indicator directly on the cam lobe itself, The actual readings i got were I=.314 and E=.329

cam specs from the Crower web site:

The information below is for degreeing cam only. Correct only at .050" tappet lift.
INTAKE Opens: 6.0 BTDC
Closes: 42.0 ABDC
EXHAUST Opens: 54.0 BBDC
Closes: 2.0 ATDC

LOBE SEPERATION 112º


Duration at .050" Intake: 228
Exhaust: 236
LOBE LIFT Intake: 0.319
Exhaust: 0.33

[LA360Dart]

rb77413

?? did you measure the lift when you put it together. If you didn't the lift may be what it was when new. The cam specs. .478/1.5= .3185 intake and .502/1.5=.3345. These are just .004 to .005 larger. The numbers are just to close to be a coincidence. Could the cam have been small to start with? Kinda odd to both wear just .004 to .005".

dwc43

1) Did you just say what I thought you said? If he measured at the lobe, lifter body or plunger it makes ZERO differance. The cams lift is not changed unless he allowed the plunger to move down while measuring the lift. A spring in a dial indicator won't cause the spring in the lifter to depress. Your latter statement is right on but the first one is off in the ether.

2) The second post is even worse. The lifter had bled down then it's at bottom of the lifter and lobe lift is unchanged. Suppose that you have a series of pullies and a rope theaded though you move the rope 6" at the start how far does it move at the end? Pulley ratios works out to 50:1

3) Sorry to be so harsh but that is tragic and you build race engines scary. Hope your a better in your law enforcement job.

[dwc43]

So you lost .005 on the intake and .005 on the exhaust. Well at least it's euqal wear so the valve springs must be right. How many miles on this cam?

[dwc43]

Originally posted by LA360Dart
rb77413

?? did you measure the lift when you put it together. If you didn't the lift may be what it was when new. The cam specs. .478/1.5= .3185 intake and .502/1.5=.3345. These are just .004 to .005 larger. The numbers are just to close to be a coincidence. Could the cam have been small to start with? Kinda odd to both wear just .004 to .005".

dwc43

1) Did you just say what I thought you said? If he measured at the lobe, lifter body or plunger it makes ZERO differance. The cams lift is not changed unless he allowed the plunger to move down while measuring the lift. A spring in a dial indicator won't cause the spring in the lifter to depress. Your latter statement is right on but the first one is off in the ether.

2) The second post is even worse. The lifter had bled down then it's at bottom of the lifter and lobe lift is unchanged. Suppose that you have a series of pullies and a rope theaded though you move the rope 6" at the start how far does it move at the end? Pulley ratios works out to 50:1

3) Sorry to be so harsh but that is tragic and you build race engines scary. Hope your a better in your law enforcement job.

Just need to explain it better I guess. In hte first post I was refering back to the fact he check it at the lobe and the lifter. I know I did not make that very clear at all after I reread it myself. The second one was giving two different scenarios again. And just because a lifter bleeds down does not mean it will completly bottom out. It has a set of check balls in there and no lifter will completly bleed down til theres no oil in it at all. Sorry for any confusion there.

[rb77413]

I didnt put this engine together. The previous owner was sure it was one of 2 cams. Wgile the intake was off I decided to measure the cam. The cam I believe has only about 10K on them. Thanks guys. More than likely I guess the cam was on the small side to begin with.

[sixpackgut]

isnt a cam lobe ground at a taper from front to back to spin the lifter and prevent cam walk? if you checked it at the lifter i would think it would be more accurate. i have checked a couple cams lately and they all have been in the ballpark but smaller than what i thought they should be.

[rb77413]

Originally posted by sixpackgut
isnt a cam lobe ground at a taper from front to back to spin the lifter and prevent cam walk? if you checked it at the lifter i would think it would be more accurate. i have checked a couple cams lately and they all have been in the ballpark but smaller than what i thought they should be.

I did think about that, and tried to get it in the middle of the lobe. When the heads come off I will prolly use a sloid lifter to check. Cool, at least now it doesn't seem like i need to replace the cam.