What would cause on lifter on a sbc to wear completey out.  Good Oil Pressure and nothing else notibly wrong.  

Not all that unusual, back in the late 70s early 80s it got so bad that there was a law suit an subsequent recall or payment to settle. The consesus was faulty wear resistance treatment which I think was Parkerizing. In my less than humble opinon the real Root Cause is the the lack of positive cam retention. Everybody else uses a thrust plate which positively restrains the for and aft camshaft movement. Chevy puts a small angle on the lobe and used valve spring pressure reacted through the lifter to push the cam toward the back of the engine to react forward cam movement. Only rearward movement is positively restrained by the back side surface of the cam gear to block. This arraingement allows sufficiently strong loads to move the cam for and aft in the bearing bore.  As the timing gears and chain age I think the cam starts getting fore and aft as well as back and forth ossicallations that exceed the thrust seating force generated by the lobe taper. These ossicillations then drag the cam lobes horizontally across the lifter faces. A little bit of this kind of motion is plenty to take out the lifters and often the cam lobes. This often shows on only one or two lobes and lifters, while extreme cases get most if not all of them to some extent.

This is a long way of saying that a cam button on non factory roller blocks is a good idea regardless of cam but especially with anything that offers durations over 200 degrees and lifts over .4 inch. Keeping up on timing chains and gears is a good idea; i.e. every 50,000 miles on a stock non performance engine. The nylon gear and silent link of the factory cam drive offers some isolation from crank ossicillations, but they wear quickly. Steel gears and silent link chains offer an improvement in gear life, but the silent link chain still stretches, still this is a better deal than the OEM, but it also allow more of the crank vibration to the cam. True roller chain and gears offers the best service life, but will transmit still more crank ossicillation to the cam, but this set up combined with a cam button is the best way to go. A cam button should be included no matter what the camshaft timing and lift or cam drive selection. High RPMs, wild cams, stiff springs, 1.6 rockers, improper length or bending pushrods, worn guides & rockers, tired hydraulic lifters or using solid lifters, reving to lifter pump-up also are major contributors to cam and lifter wear problems. 

My 2 cents from a lot of shop time inside these engines; Bogie 

I was just going to say perhaps the rocker was lashed too tight,  but what he said sounded alot better.

Brian

Thanks guy's.  I broke it down and found that the Cam lobe for cylinder 8 exhaust was gone.  The engine only has about 3k miles since a complete rebuild so I am guessing that the Cam was not properly broken in.

Go here   http://www.cranecams.com/?show=article&id=2

Follow these instructions to a "T".

Never ever reuse old lifters on a new cam. That means, you guessed it, take all the lifters that have 3000 miles on them and put them in the recycle can.

1) Coat the new cam and lifters with gobs of moly cam lube.

2)  Prelub the engine with a electric drill driven adapter to spin the oil pump.

3) Don't crank and crank if you can't get a light off --- find out why. Grinding away wipes the lube off the cam and lifters faster than the oil pump puts it on. The "moment" to which the lobe and lifter is exposed to by the valve spring is greater during cranking than when running because of the slow rotation rate of the engine on the starter concentrates the load in small areas of surface for a relativly long period of time, this squishes the lube out and causes high local heating from friction at the contact interface.

4) If you're running a whomper-stomper cam with stiff springs, use GM run of the mill passenger car/truck springs when breaking in the cam. The lighter pressures go a long way toward preventing break-in lobe and lifter failure. After the engine has an hour or two on it then replace the spings with the "race" stuff.

5) Once you get the engine running keep it around 2000 RPM with no load (don't drive it) for about a half hour. Then drop it to 1500 for a the rest of the hour. Have a couple good size fans to provide cooling air through the radiator and into the engine bay. Do not allow the engine to overheat!!!!!!

6) Put a cam bumper in it, to be effective you'll need to reinforce the timing cover to keep it from flexing. This can be a piece of 1/8th to 3/16s thick by an inch and ahalf square piece of steel welded to the out side of the timing cover, or an external bolt run between the water pump and the timing cover, many aftermarket pumps have a provision for this, if your's doesn't use a stud in the lower backing plate hole of the water pump. Best is to spring some bucks for a cast aluminum cover which is sufficiently stiff as to not need additional reinforcement. Stay away from chrome covers unless this is strictly a show engine. Chrome, significantly reduces heat transfer which causes the internal components and the cooling system to run hotter and work harder. A two piece timing cover that allows for timing set and cam work without dropping the pan is a great asset.

Bogie 

Thanks oldbogie, you are great.  HOwever I am a day late and a dollar short.  I should have checked this site yesterday for your advice.    I installed a used good condition General Kenetics CaM With New lifters, tons of Cam lube.  Fired it up and ran it at 2000 rpms for about 15 minutes.  Let the engine cool overnight and yesterday adjusted the valves.  After that I decided to take it for a short spin since everything seemed ok.  I didnt make it out of my neighborhood before the engine started missing and backfiring through the carb.  ONce i got it back home I pulled the valve covers and noticed that they were all loose again......... so I broke it back down and found that Mostly all Of the lobes on the cam had worn off to nothing.  THe number 8 eshaust lifter also worn and a different pattern that the rest.  It has a extremely gouged pattern. Help Help Help.  All that I can think to do differently next time is prime the oil pump as you described.  HOw do I do this?  Help Help.. THis is beginning to break the bank..

is it hard to get the #8 lifter out, the one thats wearing so badly?  perhaps its in the lifter bore.  ok bogie take it away

Wow that 's an experience to the extreme. If I could get the cam out without doing more than raising number 8's lifters just enough to let the cam bearing journal slip by I'd hold off and push them out the bottom, assuming you're tearing the engine completely open at this point. That would minimize any damage to the lifter bore resulting from driving the lifter back up the bore to get it out. Your problem could be related to worn or miss-aligned lifter bores.

At this point if you could describe the build up for me in terms of what machining and what parts your using would be most helpful. It's quite unusual for a cam and lifter set to go away so quickly, so I'm on a hunt for something out of the ordinary that was or was not done during the rebuild and what parts are in there.

Prelubing the engine is accomplished with a tool either bought or made for that purpose. The tool is essentially a distributor with the drive gear removed from the bottom of the shaft and the mechanical advance plate cut off the top. This (what is it a gadget or a widget?) is installed into the distributor opening so it engages the oil pump drive shaft. An electric drill is used to rotate the "distributor" shaft which then rotates the oil pump, all without disturbing the cam. This is done till oil is coming out the pushrods, showing that the engine has been lubed with pressure oil. Then you remove the "tool", drop in the real distributor and light the engine off. This is especially important to do with an engine that's been setting awhile between building, installing, and running.

The cam and the bottom of the lifters are 100% dependent upon crankshaft throw-off and upper end drain back for lubrication. That's why it's imparative to get an early light off and keep the idle speed high for a while. The "dry lube" materials in the oil such as zinc dialkyl ditiophosphate (ZDDP) need time work into the pores of the cam and lifters, this stuff is what provides long term protection at start-up after the oil has had time to drip or evaporate off the engine internal parts when it's not running.

At this point you've got a lot of metal inside the motor, I, therefore, would highly recommend you pull it out and do a complete dissassembly and cleaning before running it again. The fine metal particles from the failed cam and lifters are often too small for the filter to pick up, not all the oil goes through it all the time anyway, and this stuff acts like a fist full of sand going through and opening up clearances everywhere.

Bogie