Thread: "Walking Cam" Problem

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I have a street 100 over 427 BBC. Last summer after I had body work done on the car, I started it up. It ran fine for a day or two, then I noticed some valve clatter. So I readjusted the valves following the procedure point by point. After, I stated it up, and the noise was gone. However, a few mins later there was another, louder noise comming from the motor. After some investigation and help from other car guys in my area we narrowed it down to being the cam. the cam is said to be "walking out" and hitting the timing chain cover. I've tried just about everything to stop this noise. The best ive done is when I readjusted the valves, the noise seems to stop for a minuite or two, then it will start again. Any suggestions at all would be a ton of help, i really wanna get this car on the road for the upcomming summer.
Thanks all,
Ben

Originally posted by Bengiordano
I have a street 100 over 427 BBC.

Not sure what street 100 over is?

Cam button might help. Slides in the center of the cam gear and held in place by the cam gear bolts. button comes to a dull point. The point (button) bumps the timing cover to keep the cam from "Walking out".

If you have to keep adjusting the rocker nuts down to get your settings right, or to make the valve train noise go away, you could be losing the cam or lifters. What type of cam is it?? The only type of cam you need a button with is a roller cam. A flat tappet cam will not walk under normal circumstances. The lobes are angled slightly so that the rotation against the lifters keeps pushing the cam towards the back of the engine. If it truly is hitting the timing cover, something is drastically wrong. And if you have to keep adjusting valves, the cam or lifters are on the way out. You have to do more checking. Are you using standard rocker arm nuts or locking type? If they're the old standard nuts, they're only designed to use once, and they can lose their holding capacity. They might be loosening up. Either try new nuts (they're cheap) or if they're locking type, there is a problem. What makes you think the problem is in the cam walking? It's possible, but very unlikely. Keep us posted. John

They are Hydraulic cam and lifters. Cam is deffinatly hitting the timing cover. If you start it up and place you hand on it, it's completly obvious. I have changed the cam button as was suggested before by the local machine shop. This did not change anything. I'll try to post the part numbers of both the cam and lifters, as soon as possible. I'm using the nuts where you lock the allen head inside and against the hex nut. As far as the cam and lifters being worn down, i rebuilt the motor about 4 years ago, and only drive the car in the summers, is it possible for them to be worn that fast? Another thing that i thought about was that last year i had body work done on the car, and it was not started for a pertty long period of time (6-8 months) could this have hurt the lifters or carm? Keep the replies comming, i wanna fix this thing!!
thanks guys,
Ben

I think I would stop there and tear it down before you wipe it all the way out....

I am gonna say too that you either got a lobe or a lifter that is wearing away....This will send tiny metal particles thru the engine and take out the rest with it....Bearings and crank....

As mentioned under "normal" circumstances flat tappet cams do NOT walk....

You got something goin on here that requires attention....save your wallet and yank it and tear it down...

Normally in a car you don't drive they should be started at least once a week especially in a bigblock engine... The camshaft relies solely on splash for lubrication and if you do not start it over long periods of time you are running it after all the oil has dripped off ( running dry) by the time oil gets splashed back on it's usually too late... You can get lucky but sometimes you don't....I would recommned biting the bullit this time and go with a roller cam and lifters.... sure they are expensive and they'll live rebuild after rebuild.....sorry

Do you think a complete rebuild is needed? or could i get away with just cam and lifters? I have run the motor a total of about 45-50 mins since the problem has started. Thanks again for the advice,
-Ben

depends on how far it has gone...

If you catch it bore it gets out of hand you may be ok....but, if a lobe has worn all the way off or the lifter is noticably shorter than others than you know that metal is floating all over inside the motor..... I would atleast do a tear down and inspect.....

I lost a cam in a 454 a year ago and it had and I re-hot tanked it and used the same bearings. They had no metal fragmenting but everthing else needed a good cleaning

First you have to figure out why the cam is moving, or if it is. If you already have a cam button in, and it's touching the front cover, which it should be, that could be what you feel...in that case, nothing is wrong with the cam "walking". On the other hand, if you have either one or more lobes going away, and corresponding lifters, you pretty much are screwed. It doesnt matter how long you have run it, I have seen cams go flat during break-in, only 10 minutes....if it has gone enough for you to hear the clatter, then there is lots of metal floating around in your engine...the oil filter will have caught most of it, but lots still gets in the bearings. I just tore one down in which two cams in a row were lost, and all the bearings were shot, along with the crank shaft...it is scored and has to be re-ground. You can just replace the cam and lifters if you want, and change the oil and filter..you might be OK for awhile, if the bearing wear isnt too bad. Or you may be in for trouble, there is no way to say for sure. It would be a gamble. If you do that, watch your oil pressure carefully. If the bearings are wearing out, the oil pressure will start to decrease as the bearing clearances increase. That will be the first sign. It's a tough call, I know you dont want to tear it down, but that's the only way to be sure of what things look like inside. I doubt that not starting the engine for some time is what caused this. It must have been going on since the rebuild. I had one go after about a year once. It happens. What kind of cam is it? Brand name, I mean. What Dr.Bowtie says is pretty much true, I have a roller cam now because of a couple of failures. If you do decide to go that route, let me know and I'll save you some money before you buy anything. Good luck, and whatever you decide to do, keep us posted so we can help. John

I'll second what Johnny said I have had cams go during a break in and two after a year.... after that not many...

If I go for the rebuild, and it looks like i dont have much of a choice. Whats to stop the same thing from happeneing again? What should I do so that I know I wont have this same problem a few years from now? Why would the cam start wearing down after the first rebuild if not because of not starting it for long periods of time?

By the way it is a Crane Cam
-Ben

Flat tappet cams are a gamble....

They are case hardened and sometimes maybe one just didn't get fully treated? dunno

One time I did 3 engines the same and used they same cam for all 3...

two of those went bad in a month the other was fine....pulled the 2 bad ones and sent them back and I got 2 new cams of those of which 1 was bad....one engine got a cam 3 times before I went to something else... All the cams were Speed Pro's (sealed power)

The lobes that went soft were either #1 or #8 none other? I have used every lube other than axle grease....may try that sometime....

There is no nothing to say it won't happen again....Just makee sure you do exacty as the cam instructions say for installation and breakin so atleast the warranty will be good....

Is it possible the rocker arm nuts are at fault? Depending on valve spring pressures the adjusting nuts could be backing off their adjusted position.

I have positive lock nuts on my BBC, they're nothing more than a nut with a set screw.

Also if you tear down the engine make sure the machine shop hasn't placed the cam plug at the rear of the engine in to far.

Good luck.

Quite a few things will cause the cam go go away....but Im convinced it happens at startup or shortly after. Mostly it is either not enough cam lube, or too much cranking before the engine starts, which wipes all the lube off the lobes and lifters. Spring pressures play an important part too, make sure the springs are what is recommended by the cam mfgr....Set your timing as close as possible so the engine will start right away, and make sure there is gas in the carb float bowls. When you put your lifters in, make sure they turn freely in their bores. A lifter that doesnt turn when the engine starts will wear out in no time. Follow the instructions to a tee, and you'll probably be OK...at least that way, if the cam does go bad, the company will no doubt replace it for you, like DrBowtie said. Best of luck to you, hang in there. Hot rods, nothing but trouble, huh???

If it were my engine I would check the engine for filings first. If the oil is clean I would check the adj. nuts on the rockers. (The two easiest things to diagnose).
If you do find filings in the oil ................... that sorta' narrows your options...... but I would rule out the simple things first so you don't pull the engine apart for no reason. Just my 2¢.