I'm replacing my Comp cam due to an issue with whining.

I was sent a cam with the same grind, but I figured for giggles that I would compare the lobes.

Using calipers I measures the first lobe on each cam, from base to tip, but I'm coming up with different numbers?

I'm guessing this shouldn't be the case... Or is there more to it?

Cam (a)= 1.7815 base lobe to max
Cam (b)= 1.7695


How should I measuring?

 

Why are you measuring the cam? Taking dial calipers to the lobes isn't going to tell you anything that isn't on the cam card. Actually, it won't tell you much of anything at all. Also, you could be measuring in ever so slightly different spots from cam to cam.

If you want to know more about the lobes on your cams, get a degree wheel and dial indicator and degree the cam and record lobe lifts for every degree of movement. But that still won't tell you anything unless you understand cams enough to design them in the first place.

Good luck though, that's the kind of info I like finding out for myself also.

 

If you also measure the minor axis (perpendicular to your meaurement above of the major axis) and subtract this from the major axis you get lift...

but as was said above you don't have durartion/LSA/advance or valve events.

 

I was simply trying to see if each cam was identical... So that I could pop it in and go.

Knowing the lobes are different, I'll have to likely order another set of pushrods, I assume.... So dropping another $100 because of a poor cam polish upsets me.

I didn't want to put the cam in until I was sure, which is why I resorted to the calipers.

I would have assumed both cams would have the exact lobe height, but I've measured on different spots of the lobe (towards the ends... Middle...etc) and each time moving the caliper from one cam to the other, you can visually see the difference.

 

Put the cam in the motor and remeasure push rod length and you will know.

 

Maybe I'm looking at this wrong, but you pulled the old cam suspecting it's bad, found a measurement difference between the two, and suspect there's an issue with the new cam?

To me, I would assume the old one was a known issue, a brand new "identical" cam measures differently, then I would take that as confirmation the old one was bad.

 

The only reason you should need different length pushrods is if the measurement for the base circle of the cam changes. But it is a good habit to always measure regardless.

 

I'm just wondering if a grind was done wrong once, then what's to say this new one is correct? There doesn't seem to be any safeguards or checks/balances.

The only issue I found with the cam I had was a whining noise... Which many here attribute to a bad polish... But I had no idea my cam lobes were off.

I know Comp Cams makes thousands of cams, and generally don't have issue, but I don't have a lot of trust in them right now...

 

That's why I like Kip, you get a cam dr report, which tells you everything you need to know and a lot of stuff you didn't need to know about the cam. The only way to truly measure it is on a cam dr. You could send it to Kip for validation. You could send both to Kip for validation and then you'll know for sure.

 

Wayland I thou th t you got a cam motion piece now? You got another co m p one?

 

Yea, they offered to swap it out under a warranty (with a deposit of course).

I wanted a cam motion one, because they seem to have some better QC measures in place, but I was told that even cam motion had a bad batch of cams, and with the amount of Comp Cams that they sell, only a handful ever have issues.

I might just say screw it at this point and order a Cam Motion cam. I'm not sure they can give me a BTR grind (the Cam Motion shelf grinds seem to have less lift) but I just like the idea of a report card proving somebody checked the cam after it cam off the machine.

 

You can set the cam up in a pair of "V" blocks and use an indicator to compare base circle numbers to know if your old pushrods will work for you

 

Cam motion custom grinds cost the same as there shelf cams. So all you need are the BTR specs and they can make it exactly the same.

 

We have not had a bad batch of cams in last 10 years. Is we ever have a problem with any of our cams we replace them at NO CHARGE. If you want to make sure of what you have and to make sure the new cam does not WHINE send it to us we will put it on the Cam Doctor give you a report and polish it.
To check the lobe lift it must be done with a dial indicator. When you measure the lobe heel to toe or 12&6 you will get a number like you did. When you measure across the lobe 3&9 you will get a number. The problem with the 3&9 measurment is you will be on the opening and closing ramp they go past 90 degrees so the number will be a little large. When you subtract the two numbers the lift will be off a little.

 

This really is your best bet. You'll be down a couple more days, but then you'll know FOR SURE about both cams

 

Hey Kip,
I sent you an email using the form on your website. Let me know if you got it or not.

But regardless, are you saying two of the exact same cam grinds could be off like I'm seeing?

And as an aside: I noticed on both comp cams that the hollow core seems to have a weird look to it: almost as if they drilled in from each end, but didn't meet exactly in the middle? Is that typical?

 

You could have the same grind with a little different base circle that's normal. The lift and duration could be the same but they will measure different heel to toe. PM me here to make sure I get what you sent the web site emails can get lost sometimes.

 

I see. It still seems odd to me that two of the exact same cam grinds could be off a noticeable amount despite being ground only a couple of months apart. I know very little about the process, but to me it just seems like a quality control issue.

I'll shoot a PM now!