So I freshened up a motor to include a new cam. Once installed in the car it just never was right. And after a lot of troubleshooting, parts, ect, I took the motor back out and took it apart.

Three of the pistons showed marks of contact by the intake (yes, intake) valves. No damage, but certainly curious. Re-degreed the cam only to find out nothing wrong there.

Put a new smaller cam in it, and now runs like it should. So, looking at the old (but new when installed) cam, the intake and exhaust lobes on number 6 and number one don't line up. Close, but no cigar. Visually about .100 off from another. I didn't check any other lobes.


Anybody else ever have that problem? Wow, what a nightmare it has been.

The only real way to know if there’s an an issue, and if so, how much of one...... is to degree every lobe.

I just used a 590 cam with no problems engine runs great.
purchased about four months ago. Keith

I've had a couple of 590 cams in our cars and its a great cam. But the effort I went through to fix this problem was just about enough to drive ya crazy. Just an odd lot of bad luck.

I'd use one again some day, but I'll eyeball those lobes prior to install and maybe degree in a couple of cylinders while I'm at it.

Agreed, I woulda not have expected that error!. A good reminder (for me) to check everything/assume nothing.

A good engine builder would check a phase of a crankshaft but we all just assume the other 14 lobes are phased properly.

Theoretically, it could also be the crankshaft's phasing.

Clearance is never a problem until things get too close. You will never know unless it's checked.

Its definitely the cam. You can "eyeball" down the length of the cam and see the cylinder 1 and 6 lobes are off from one another by about .100 at the center of the lobe. I suppose I could check 8 and 5 too. But if they did line up, that would only show that cylinder 1 is off. But, any of them off, I'm still bad.

When you have a new crank, I can see that being checked, this crank was run before. I checked piston to valve clearance, but only number 1. And when you do that, typically only the exhaust comes close.

Maybe from now on I'll check 1 against 6 when degreeing. But someplace along the line we all rely on some quality check somewhere. The jig on this cam had to have slipped, eh?

What made this such a tough deal is that I fought with these problems for a long time. It ran, it idled (although somewhat erratic), didn't rev very good, never past 4500. I did drive it locally, just never performed. Who would have thought?

Did you call the manufacturer and tell them what you had?

Might want to do that and ask how this could happen when a master is used to grind a cam.
Unless maybe they don’t use a master any longer and use CNC.

If you decide to have that conversation, you do not want to be dealing in "abouts" either. You need to mount the cam in a lathe, set a dial indicator on the base circle and measure the lobe lifts on the offending lobes and the rest of them for that matter to the .001".

Calling tech support with an I eyeballed it to about .100 story might activate the dial tone. Lol

Kevin

I'm not calling anybody. Not worth it. Just a loss.

The cam is put in a jig, ground, rotated/ indexed on the jig, and go again.

Something had to happen that it got loose, slipped, or whatever.

Here’s something for you to think about.......

If you took the same cam profile, but had it ground on two different lsa’s, say..... one at 100, and the other at 120....... do you think the alignment/relationship for those two particular lobes would be the same between both cams?

Between the two cams, no, the lobes would be offset from one cam to the other. But, on the same shaft, the 1 and 6 should always line up. Well, that is my current thinking anyway.


Per your question, I did go out and look at another cam I have and although different lift, the 1 and 6 do line up.



BtW, if this was a cam company, I might give them a call and see if there is something they would do. But, its a Mopar cam. Can you imagine calling them? I bet it would take a half a day just to find someone who would listen.

Never thought deeply about this before, but wouldn't all the lobes on the cam be cut in 45 degree segments?

I have a friend that used to work at Schneider Cams in San Diego, he might know how it happened to fail. Next time I talk to him I will get his take on it.