The 350 we put in my girlfriends 85 Trans Am keeps eating cams. By eating cams......I mean that every few months, the cam will pre-maturely wear out a lobe or two. I know this because the car will develope a stumble, then when I take the valve covers off to check the rocker arms, the guilty lobe will not move hardly at all indicating a rounded lobe. This has happened THREE times on the same motor. I've done maybe 50 cam swaps in my life so I know what I'm doing. This never happens on my firebird or any other car, just hers. The 350 we got was out of the junkyard in good used running condition, mileage unknown. The motor appeared to be "refreshed" recently, as all the freeze plugs were new and the paint was fresh when I bought it. Ridge wear on the cylinder walls was also very non-existent. Motor looks very good. I basically just refreshed the motor with new gaskets, new oil pump, put on my old vortec heads with new Comp conical valve springs, and threw the motor together with a comp 268 extreme energy cam. Now I'm scared to fix the bad cam for the third time as it will just happen again.....I need to figure out why its doing this!!! Any ideas??

 

I had two comp extreme energy 294 (big block) go out on me, both lasted a week or so before sheading a lobe or two. Comp said it`s my block and feed me BS about geometery and such. After they "eat" two under warranty they gave me a old pro street style cam that also had a 294 advertised dur. It never had a problem. All I use now are wheels man. Most cam faluires are caused by poor break in, I`d make sure you hone out those lifter bores so that tappet spins freely, if it jams and doesn`t spin you know what happens, dished lifter. The metal from those lifters ruined my 454, the skirts of 3 pistons scuffed till they knocked.

 

same lobe? i'd suspect maybe a weak spring or the lifter bores. new lifters with the new cam?

 

Why am I not suprised it's a Comp cam? Because my engine ate two lobes on a Comp cam on break-in. And most "eating cam lobe" threads for some reason involve a Comp cam. Coincidence? I don't know.

I'd do what greezemonkey says and check lifter bores and for any coil bind. Good luck with it.

 

ALOT of 70s 350 blocks have one of 2 Problems; either The Starter Problem, or The Lifter Bore Problem, or maybe even both. The one with lifter bores is where one or more of them don't point properly at the cam, so the point of contact between the cam and lifter isn't right. The more aggressive of a flat-tappet cam you put in there, and the more spring pressure you run, the more critical this contact is.

Is it the same lobe over and over? If so, your block may very well be fornicated, and should probably be trashed. You can fix it by boring them to the AMC lifter diameter and using AMC lifters. But usually you can get a new block for less than it costs to do that. And of course, that has to be done with the new bores properly indexed to the cam, or you'll just re-create The Problem.

If it's eating the same lobes repeatedly I'd just throw the block away if I didn't have a bunch of money already tied up in it; stuff like 4-bolt splayed caps, or stroker grinding. 350 blocks are too plentiful to get attached to one particular one.

But I also notice you have Vortec heads, which have a known retainer-to-guide clearance issue. Have you checked that, to make sure the retainer doesn't smash into the top of the guide at full lift, and basically force the cam to try to press the guide out of the head?

 

Maybe I should post a new thread, but I've had a similar problem.
I had an engine with a cam that wore down a lobe prematurely, and I just recently invested in having that same block machined. Unfortunately I wasn't aware of this problem til after I had the work done.
But at least the engine isn't assembled yet and I'd like to know if there's a way of checking the lifter bore alignment before I go any further.
Any ideas??
Are there any particular block #s or series of #s that are prone to this problem?

Thanks

 

I don't know of a good way to check, other than a machine shop that has the right equipment and expertise. Basically, find a racing machine shop that builds circle track cars where they know and use the tricks like the AMC lifters; yerbasic corner auto parts store won't cut it.

Call around to the shops in your area. Just say the words "AMC lifters" and see what you get. If you get the phone equivalent of a blank stare, thank them for their time, and hang up and call the next one. If they want to know who let you in on their secret trick, you found a match.

Any 70s block can have this. I've personally owned 010s and 014s that had it, and maybe others that I can't recall the casting #. It was a machining problem all through the 70s, just like The Starter Problem (where the starter bolt holes are drilled toof ar from the crank); so, based on the odds of that, which are about 1 in 4 or 1 in 3, and it being caused by one of the 3 or 4 machines that performed that operation being wacked, I'd guess your odds are about 1 in 4 or 1 in 3.

Chances are, if you buy a 350 block from the 70s and it looks great, looks like it's running maybe even, you can't see a thing wrong with it by eye, and you can buy it for real cheap, like way way too cheap, it has one of those Problems and that's why somebody's getting rid of it. Whether they know the cause of it or not. All they know is that no starter they've ever found will work right on it, or it's eaten 4 cams so far, and they're sick of it.

 

That was fast, thanks.

 

I just KNEW that if RB saw this, he would be compelled to reply with information about "The Problem".

 

To be completely honest, I don't remember if it happens on the same lobe repeately, but I DO remember that in at least one occasional of the SEVERAL times this motor has eaten a cam, it was on the #3 cylinder, and this time its on #2. They were all Comp Cam extreme Energy 268 cams, and the heads are vortec, however they have been modified with different aftermarket teflon seals and comp conical springs. I shaved about .100 off the top of the guides with that tool to install the aftermarket seals, so I don't its a guide to retainer contact problem. i'm really wondering if maybe I should just find another cheap 350 short block, do a cheapo rebuild with some $80 pistons and put together another 350, because I can't afford (either time or money) to put in another cam every 6-12 months because this motor keeps eating them. Its a damn shame too, because when her car is running good its FAST as hell with those ported vortecs, gears, and automatic. It ran a 13.7@101 last time at the track WITH the worn #2 cam lobe. I bet properly running her car would pull a high 12, since the same exact motor in my firebird with a manual tranny went 12.6.

 

why don`t ya just put some roller lifters in it, more power, no lobe eatin` and peace of mind for just a little more than a few cam and lifter kits?

 

I bet I know why.....because retro rollers = $$$$$!!!!

But worth it in the long run, I agree.

 

Probabily the lifter bores.
Try this. use a cam with a little less volitile lift ramps.

try a Summit #1103 214-224-.442-.465-112
A little easier on the whole valvetrain.

Went 13.0@105 with a basic vortec headed 350 like yours, so this cam can deliver the goods.

Wolverine Blue racer #WG1159 is the same thing.

Sometimes lifting the valve off its seat just as fast as posssible, is not the best for reliabilty.
the Comp extreme energy cams push the limit in this area.

Also note: that the car manufacturers have lobbied the oil companies to remove the Zinc out of engine oil. ( (emissions)
The Zinc is one of the best anti wear anti scuff additives
in oil. This will result in more flat tappet cam failures.
Add some GM E. O. S. engine oil supplement to your oil.
This is good stuff. you have to go to a GM dealer to get it.

Check out the tech note from LAZER CAMS

Here is another good source for this type of cam.
And others.

Accelerated Motion Cams

Will ship to your door too.
A-motion pn# 19811-21578 Is the same grind.
All his stuff is hand checked for accuracy before shipment
with a Cam Doctor and includes the cam analysis print out. Good warranty. Great quality.

 

Sorry to bring this thread back from the dead, but I just tore an engine down after it ate a cam and I was doing a searchon the topic.
So the question is, what's the deal with the AMC lifters?

 

They have a bigger diameter, so that the lifter to cam contact area is less severe. It allows for more radical cams profiles. So if you have a xtreme energy cam, a radical lobe grind, the AMC lifters will better handle the force and stress, because the lifters will not gouge into the cam lobe.