Cam Pitting

[mhoffman]

Over the weekend I found some light pitting on the top of one cam lobe; I searched and could not find any other posts as to when it should be replaced. I have the engine lowered (but not removed) in order to replace some leaking oil cooler seals. Car is a 79SC with 110K. None of the other cams have any apparent wear, heating issues, or pitting. All of the studs are in tact.

I have spent the last few weeks attending to a lot of "little" things that had been neglected by the PO; I figured as long as I have everything apart, go ahead and get the caqt to a good new baseline maintenance program, in addition to do a few upgrades- SSI, M&K muffler, wires, plugs, clutch cable, etc. I'd like to get the car to where I know what the status of all of th emajor components are and the go from there.

My question is 1) should the cam be replaced and 2) how much "pain" (read time and money) would be involved?

Thanks for any input-
Matt

[cstreit]

Try searching a bit more in the engine rebuild forum, we've discussed it several times. General consensus is that some small pitting is okay, but if it progresses, they'll need to be replaced.

To replace them you can either do a partial drop, or pull the engine. To remove you open the chain boxes, valve covers. Remove or loosen the rockers. Engine at TDC. Mark them remove cam nuts, sprockets, chain etc.. taking care not to change timing. Pull cam, replace, reverse assemble taking care not to change timing. Reset valve lash, check valve timing. It's not an easy job but can be done at home.

I would guess it's 8 hours of labor in an independant shop off the top of my head.

[mhoffman]

I priced new cams and still breathing through the oxygen mask....

[preston_brown]

Originally Posted by mhoffman

I priced new cams and still breathing through the oxygen mask....

You won't need new ones. You can have your current ones reground (and rehardened, if necessary) for a much more economical price. Check out

http://www.drcamshafts.com

or

http://www.webcamshafts.com

[KTL]

Yep. They can most likely be reground. Light pitting is easy fixed by Dougherty. Even a bad pit could be fixed with what's called hardwelding and reground.

Don't worry. New cams are NOT needed.

Your issue is probably not actual pitting from abnormal wear or lack of lubrication. Probably just a casting flaw. A search of the forums will show you that plenty of people's cams have this problem. Key to avoiding this is make sure you use good oil when you're done fixing everything up. The vast majority of today's SM rated oils are not utilizing the additives needed for the 911's flat tappet valvetrain.

[DaddyGlenn]

I found this last year during my first engine drop...



I buttoned it up and have put another 12,000 miles on her since. She is now sitting in the garage waiting for me to drop the engine again. I will be having the cams reground to a 964 profile and do some other "while I'm in there" stuff. My hope is the extra 12K didn't hurt too bad.

[Steve@Rennsport]

Those are likely oil-related problems (unless the spray bars are partially plugged) and we've been seeing this in increasing frequency for the last 3 years.

Personally, I would not let it go since the the metal that flaked away is VERY hard and will be pumped through the bearings,....thats not a good thing.

I would suggest that you review what oils have been used as well as how often its been changed as thats the real key to preventing a recurrance.

[Scott R]

My cams looked like Glens, maybe worse. I could never get the valves set correctly as a result. John at DR camshafts welded and re-ground them to 964 spec, beautiful work.

[mhoffman]

Thanks all- mine look similar to Glen's though not as pronounced (Sorry Glen!). The blocked oil flow or bad casting makes sense since the problem looks to be on only one cam lobe. As long as I have the engine down, I might as well get it back to gether correctly. Since I'll have to take the heads off, should I do the valves guides too, and maybe have the seats ground?

Oil going back in is Bradd Penn- bought four cases the other day before the price increase next month...

Dang, I wanted this back together by Christmas!!

[mb911]

You will not need to take the heads off as the cams will come out through the chain cases. I would suggest just getting some reground from camgrinder..

[DaddyGlenn]

Originally Posted by mhoffman

Thanks all- mine look similar to Glen's though not as pronounced (Sorry Glen!). ...{snip}

No worries. I knew when I saw those that I was in for some expense. Assuming John can regrind them I've budgeted $1,000 for the whole project, grinding, chain ramps, gaskets, etc.

I'll start a new thread when I do the project and let everyone follow along. Perhaps you'll do the same, Matt?

[mhoffman]

I ordered a new battery charger for the digital camera- probably should take photos and add to the body of knowledge the site provide for everyone. Good idea.

I sent John a note and he quoted $275 for re-grinding and $30 each for the rockers with bushings- total is less than a single new cam, not to mention the required rocker work.

Any other recommendations while I am at it would be welcomed- things to do, things to avoid, other projects.

To summarize what I've done since I picked up the car: turbo tie rodes; steering rack clean and inspect with new lube; pedal cluster re-build; new clutch cable with helper spring; SSI and M&K waiting to go on when I straighten out the cam issue; new wires and plugs; clean and inspect of dizzy with lube; replaced oil cooler seals; new sound pad; new shift bushings; new belts and filters; replaced any bad/cracked hoses; changed tranny fluid. Valve adjust and oil change after cam resolution. Anything else need to happen?

[DaddyGlenn]

I'd change the oil pressure sender on the back of the engine. It is a cheap part but can make one heck of a mess if it leaks.

I've heard that it is a good idea to replace the cam chains as they tend to stretch. (I'm not doing mine because I'm cheap and the chains only have about 60K on them) And the chian ramps should be replaced. If it hasn't already been done you might want to consider Carerra chain tensioners.

The quote you got matches my figures but when you add in the soft pieces, (seals gaskets, etc) and allow for the other things that pop up, I figured $1,000 was a safe budget.

While you have the engine out you might want to pull off the CIS and engine tin and make sure your cooling fins are not clogged with debris. And you might as well split the engine/tranny and take a look at the clutch, flywheel, T.O. bearing, etc.

And since the engine and transmission are out it would be a good time to refresh the rear suspension and ... and ... and

[mhoffman]

Glen-
I was under the impression I could do it without removing the engine...
Ben said up the thread a bit it could be done- Wayne's book supposedly outlines the procedure, but I have yet to review it. And I would just like to point out to everyone that all of this is Ben's fault- if he had not sold me the muffler for my other car I would not have been so motivated to install the same thing in this car!! With the exhaust out of the way, just seemed prudent to do some neglected maintenance.

Also, I went through the parts catalogue trying to figure out what other hardware I need to order for the project; and I am not real clear on what gaskets, o-rings, etc I need to replace if I pull the shafts and rockers without pulling the heads.

The car has carrera tensioners (recent) and I would ASSUME (big mistake probably) that the PO put in new ramps at that time- the bill only says "Aarrera Stlye Tensioner Kit"...

Thanks-

[DaddyGlenn]

Ben is correct. You can do it without dropping the engine. But it is so easy to drop the whole thing, which is what I am going to do. (It will be my second drop.)

It actually might be a better idea to do it as Ben suggests. That could prevent a lot of "while I'm in there" work.

If I remember correctly, Wayne's 101 projects book outlines the needed parts. I'm pretty sure the ramps get changed with the carrera tensioners but you might want to ask the PO about the chains.

[mhoffman]

it must be the 101 engine projects book- the other one is lacking in the cam shaft department...
but hey, it is a cool night to work on the car- low 50's upper 40's...;-)
Did I mention I like being in Florida?

[DaddyGlenn]

Yep, you're right. I just looked. It is the engine book. I'll copy the parts list tomorrow if I have the time.

[mhoffman]

ordered the engine book this am.

I got all of the rockers/arms out last night without incident. I think I am going to have to pull the muffler bracket off to get all of the chain cover nuts removed though. Buggar.

Sounds like the real challenge is removing the gear and shaft...more to follow.

John D said he is going to go ahead and start on the rockers for me so they will have a faster turn-around while I am pullin gmy stuff off- talk about great customer service!

Matt