I think I wiped out my GP2 cam........

[Guest]

Take a look at the #3 lobe on my GP2 cam (that would be the 2nd intake). It looks trashed to me. Rough to the touch and somewhat flattened. What is the world could have caused that? I know that the roller rockers are adjusted properly, all new cam followers, new chromoly push rods. I will call Richard Good in the morning and see what he says. Gotta take the whole front of the engine and the head off to redo. This ain't fun. Must have been part of that clanking noise.

The kicker is, it runs great when it gets warmed up.


Any thoughts???

 

[2wrench]

Dang, Bill. So sorry. Never heard of a cam lobe making
a clanking noise before; but, then, I had never heard
of a flapping headgasket till that happened on my
'47 Plymouth (first car, ever).

Thanks for the time and trouble to take the picture. Looks
good.

Is the lobe you mention the one closest to the main
bearing cap? I can't see much on the ones dripping
with oil.

 

[Guest]

I highlighted it for better viewing. Cannot for the life of me figure out why this might happen. There is some play in the thrust washer but not enough to do damage. Have a new one to put in. The cam is not set in cam bearings. Has about 8000 miles on it. Pulled the valve cover and will check all my valve settings, too p.o.ed tonight to fool with it any more.

 

[Brosky]

Bill,

Back to basics. Did you check the total lift to see if the lobe truly is worn? Let's look at some details before tearing anymore down.

A worn lobe will not get better as the engine warms up and the view from that angle is deceptive, at best. Get that valve cover off and watch the movement of the push rod and rocker first.

 

[Guest]

Any suggestions on what to measure to see if indeed that lobe is flattened? If it is flattened out, then the intake valve won't be opening all the way, right?

 

[Guest]

Too, look at the texture of that lobe, almost as if there were casting defects in the metal. Looks porous or pitted. Feels rough to the touch.. All this with a strong flashlight and sticking my hand up into the bowels of the short block from the bottom.

Then, to top things off, I got a drop of motor oil in my eye.
Boy, does that sting.....

 

[vettedog72]

Bill
Do you have the tappet out yet; if so, what does it look like?

You can read Crane's reasons for failure:

https://www.cranecams.com/?show=faq&id=1

 

[Guest]

Have yet to take the head off to remove the tappets. The tappets were all new, never interchanged. The auxiliary oil line seems to do the job, everything is nice and wet with oil under the valve cover.

 

[Brosky]

Bill,

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]If it is flattened out, then the intake valve won't be opening all the way, right? [/QUOTE]

That is correct and easy to compare to the one next to it.

Be careful on the edges of the cam lobe when you are reaching up there feeling around. If it is worn abnormally, those edges can get razor sharp. That, along with the oil as a lubricant, can provide some nasty cutting action to the skin.

You already know that you don't have to ask me how I know this.

Richard has never had a problem with his cams as far as I know. If the valve is adjusted properly and you have no lift, then you know it has to come out.

Knowing you, I'm sure that you did everything correctly when installing it, so I'd be surprised if the casting was bad.

You did get a brand new cam and not a regrind, right?

 

[Guest]

Everything was new from GoodParts, even the valve springs.

Even though there appears to be flattening of the lobe on the second intake, all this might mean at this point, if indeed it is starting to flatten, is there would be less air/fuel going into the chamber when that valve is opened. The push rod might be able to rotate freely when the valve is "supposed" to be coming off the intake, i.e., premature valve closure or even slow opening of same.

Am I off here or what?

 

[Brosky]

Bill,

There is a normal slight side flattening of every lobe. In other words, they are not perfectly egg shaped, but have an inclination angle that climbs from a certain point of the base circle to the top of the lobe, where lift is at at maximum and the valve is in the full open position.

Turn the engine over slowly and observe the opening and closing of the valve in question and compare it to the next intake or exhaust that matches it to see if the opening amount is the same.

 

[Guest]

With 10 and 12 fully compressed, 1 and 3 should read .018 and .016 respectively, according to the grind of the GP2. This is what Richard has told me, even thought the web site suggests .017 exhaust and .015 intake. The number 3 valve that appears to be flattened a bit reads .025 and counting...

Nothing is loose on the roller rockers, all adjustments appear true.

Even though the website Vettedog referred me to about cams and cam problems suggests cams almost never wear because of metallurgy, this sucker has porosity!

 

[Guest]

My next move, before I jerk the head and everything else, I cam fabricate a cup on a stick and fill it polysiloxane impression rubber (the kind we take dental impressions with) and stick it up onto the lobe, let it set, then withdraw it and pour it in dental stone. (How may of you can do that!?)

This should prove or disprove my dilemma.

I maintain that this is a defective cam.

 

[Brosky]

Bill,

Measure the height of the fully compressed intake on any other cylinder. Then rotate the engine and measure the height of the the spring on number 3 when fully compressed. That is at max lift of the cam, a full open valve. These should be the same.

You are measuring the clearance or valve lash/adjustment spec at .017" - .015"

 

[Brosky]

Also, defective cams do not get better when they get hot. Nor do cams with badly worn lobes allow the engine to run very well as all cylinders are not breathing the same.

Your method may or may not prove valuable to Richard in determining the correct shape of the lobe. Having something stick closely to oily parts isn't always accurate or easy, but it just may work.

And defective cams don't get quiet when the get warm and the engine is running well. If you said that the engine was loping or started to skip on acceleration or badly at idle, I'd probably agree that it was the cam.

I truly think that the noise is somewhere else.

 

[Brosky]

Bill,

I thought that you were worried strictly about a flattened lobe. I've re-read all of the posts and I just blew up your picture about 20 times, and even though it's not a high resolution, I can see what you are talking about with the potential porosity issue.

You better send this picture to Richard in a full size version.

I'd even like you to email it to me in that format.

 

[Guest]

My measurements are looking arbitrary. Especially since the battery on my digital measure is blinking.


The vinyl rubber impression material isn't sticky. Vinyl sets and releases clean.

I'm starting to get bleary-eyed. And have a headache.

 

[jessebogan]

Actually, a wiped cam will make noise. On MGBs I can tell by listening to the valve clatter. I can't really describe it, but it is a distinctive noise, differant than loose valves. Have you looked at any other lobes? It is a mite unusual to wear out one lobe. With one lobe bad, perhaps a flaw in the hardening process, perhaps even the lifter itself. If you have more than one, perhaps it is the ZDDP oil issue? I see that Moss motors, and others are selling ZDDP additives now to help protect the cams. No matter what, that really sucks.

 

[glemon]

Sorry if I missed it but with all the discussion of ZDDP, oil, and cams and lifters I am curious what kind of oil you used for break in and running the motor.

Thanks, and also a question, sounds like the cam can be changed with the engine in place, but a lot of parts need to come off?

 

[2wrench]

Bill: Sounds kinda like you're ready to tear into
her. But I can't help but think there might be
something else going on as well, and wouldn't it be
best to leave it together enough to do a little more
research so it's less of a pick and a poke?

That said, been reading a reference book on
rebuilding the Chevy short blocks. They have a
section that talks about listening to various engine
noises with a stethoscope instrument, (quoted affordable).

If you hear this noise on startup with "naked ear,"
maybe the stethoscope method can help you focus more
on an area.

In the reference, they mention different sounds meaning
different things. Where to listen. If you wanted
me to, I can copy just that portion and fax/e-mail, whatever.

Just another idea, short or ripping the engine out
without being too sure of the problem. Cam could have
a problem as well...but wouldn't you hate to install a
new one, only to find the noise is still there?

Sorry. Don't mean to have you chasing your tail.

Best of luck, Bill, and keep us posted. This one
sounds interesting.