Cam lobe measurements

[Morris]

I am trying to determine if I can get another year or two out of my cam. I really need to keep a stock cam for the short term, but I plan to buy a slightly hotter cam in a year or two regardless. Furthermore, I would really HATE to blow money (which I don't have right now) on a stock cam.

So I want to "measure" my cam to see if it is close enough to spec to keep using. I have a dial and magnetic base. My dial would not reach to the bottom of my tappets, so I turned my tappets upside down. I took measurements of #1 intake and exhaust and got a travel of about .243" on both. However, both seemed to "chatter" roughly .02-.04" at top and bottom.

So my question (at last) is this, is this "chatter" in indication of flawed measurements, or does it mean my cam is hosed? If my measurement methods are flawed, can you give me some tips on correct procedure.

Thanks

Ps. Tappets where not replaced when I rebuilt my motor and I mixed the tappets up when I reassembled /bcforum/images/%%GRAEMLIN_URL%%/blush.gif . I put about 1200 miles on the motor like this.

 

[Hap Waldrop]

Morris if the head is off, use a pushrod to set the dial indicator on for cam lobe lift, if the head is on measure off the valve retainer to give you valve lift.

Valve lift equals = cam lobe lift x rocker ratio minus valve lash.

As far as mixing lifters up, cam lobes and lifter wear together and should never be mismatched, I would start saving for that cam right now, you're going to need it. What engine 948/1098/1275/1500? If it's a 1275, if I'm not mistaken stock valve lift should be around .312", don't fret a few thousands, factory rocker arms are all over the place on ratio, but if you see big number like .020"+ drop or more, then chances are you wiped out the cam, with the lifters switched, you going to for sure wipe out a cam, probably already have. I know that not what you want to hear, but you never, ever mismatch the lifters.

 

[DrEntropy]

I'm anal over pushrods and rockers as well. All are numbered as to location on tear-down, never 'juggled'. New cams get new lifters and rods. Not a thing to try to do "on the cheap". You'll pay later anyway.

Just my couple 'a pennies' worth.

 

[Morris]

Okay... so keeping mind that my objective isn't to do this on the cheap. I am absolutley going to buy a nice street cam from APT no matter what. But I really need to get some good fuel tables for a stock cam before switching over.

Doc and Hap (and any other wise sages who care to chime in) what are your thoughts on putting in a non-nitrited regrind knowing that it only has to hold up for a year? (I plan to have the APT cam in for the big Spridget hoedown in 08). I just want to put in the stock cam, test a few setups, then shelf it. How long do you reckon a non-nitrited cam can hold up?

 

[DrEntropy]

I really hate to say this, Morris, but degradation starts as soon as you light it off. How long? Hard to say. Minutes is possible, hours likely. Your data will be inaccurate as the thing progressively turns into a set of roller skate wheels on a stick. New lifters MAY give you a bit more time, but I doubt it.

Maybe Hap or someone else will argue that. We can hope.

 

[Bugeye58]

Your not going to get any argument from me, Doc. And as those cam and lifter bits wear off, they travel through everything else, so, there go the bearings, oil pump, and all the other spinny things.
I doubt if you'll gather any meaningful data anyway, if the cam is going away as you are trying to establish a baseline.
Don't do it, Morris. You'll regret it big time in the long run.
Tuppence,
Jeff

 

[Morris]

Just to be clear Doc, my plan is to chunk the cam I have now and buy a new one. Of course, I will get new tappets, pushrods, break-in lube... the works.

The big "IF" in the situation is that the new one has not been nitrited. The seller (who actually seems like a decent fellow) claims to have 40,000 on an identical cam.

So the question is, how long will a new non-hardened grind last?

Maybe that WAS the question you were answering. Please forgive my stupidity if so.

 

[Bugeye58]

Morris, I think Doc answered that question pretty well. Anywhere from a few minutes to somewhat longer. It's too big of a crap shoot in my estimation.
Jeff

 

[Morris]

Okay... I just thought from the way he worded the question he thought I was going to keep my questionable cam.

Sorry for the confusion.

Thanks for the wisdom.

 

[Billm]

Of course when you say that the cam is not nitrided you mean that it is still heat treated to "in the 50's" I assume. In this case it should still be good for quite a while?? Nitriding is not the only way to harden a cam a (or anything else for that matter).
If it is hardened properly and you have new followers it should do OK I would thing. Am I missing something Hap,etal?
Bill

 

[DrEntropy]

There's some 'funny' metallurgy here: Cam lobes are "surface hardened". To a depth of around 0.005"~0.007" IIRC (Hap?). Can't recall just what it "Rockwell"s to, but it's 'up there'. Hardening the entire shaft would embrittle it, with dramatic consequences. If a "regrind" penetrates thru the depth of the surface hardening (and they do) it would need to be reprofiled & retreated with one of the mentioned processes. If done properly and new lifters fitted, yes it should last.

We may well be in a quandary over semantics with this?

 

[Hap Waldrop]

Nitriting goes to aprox. .030", it's the best way and what APT offers in it's regrinds. Morris, it's the get-me-by method for a year that somewhat puzzles me, what's the cost of the cheap regrind and the cheap lifters vs a APT nitrited regrind and his good lifter, a $100,$200, it that difference really worth doing this all over again in a year?
As for my opiions of personally using a poory or non hardened cam and cheap lifters, can't be of much help there, this is a path I never was tempted to follow.

 

[Morris]

Hap, the reasoning for doing it for a year has nothing to do with expense or "get me by."

I am working on a fuel injection project, and I want to be able to develop fuel and spark tables for a stock cam before setting my car up the way I want with a performance cam. It is my goal to create a business designing and building fuel injection kits for LBCs and other classic euro and nipponese cars. But I don't want to blow a lot of money on a cam I intend to through out in a year. Also, I am currently the sole bread winner for my growing family (new baby is due in May!) so it is very important to pinch pennies where possible on this project.