cam bearings destroyed

slagburn

this is a follow up to my other thread re: distributor gear failure. I tore everything apart and found the cam bearings on this 401 utterly destroyed. The engine has about 150 miles. The bearings were put in by a machine shop and aligned properly with the oiling holes. The engine was prelubed before firing and had good oil pressure. The main and rod bearings look cherry. I'm at a complete loss as to what's going on here, any insight? I do run a largish solid cam with Comp solid flat tappet lifters, any issue with those, could they cause this sort of failure? thanks..

jeepsr4ever

You did say the oil slot to the cam gear was obstructed right? I wonder if the cma/distributor egar slivers made it past your oil filter bypass and wiped the cam bearings.

slagburn

Chicken or the egg theory- the cam did have the groove machined in the front journal, however it was completely full of bearing debris. The odd thing about all this is the perfect main and rod bearings. And yes, the cam sprocket had obstructed oil feed path. So that's a possibility. The two things I was looking for on the cam are present- holes in the back, and a groove in the front. edit: one more bit of info- when I prelubed the motor on the stand the rear cam plug was out, and I was watching really close so I wouldn't get oil on the wet paint. I had a 1/2 air drill singing pretty good on the oil pump drive, and only had a slight trickle of oil coming out of the bearing. But, I'd never done that before and been able to see the results there, and carried on with installing the motor. Normal?

jeep_man_401

You did say the oil slot to the cam gear was obstructed right? I wonder if the cma/distributor egar slivers made it past your oil filter bypass and wiped the cam bearings.

On my build with my 401 the dissy and cam gears went south. The resulting mess wiped out all the bearings. Cam bearings were the worst. Oil pressure spiked and blew the oil filter gaskets. That was when I pulled the dissy and found I had big problems. I had traced it back to too high oil pressure and a possible intake coolant leak I believe. All this with less than 3 minutes on the engine.
After cleaning and brushing all the passages, new bearings I had it broke in on a dyno. Best money I ever spent!

I know they say to break in a cam with lighter springs...could be a combo of that and the casting flash. Sucks big time, been there.

What oil did you use?

Did change oil and filter right away after the cam break in?!

Anything on the oil pressure before?

Also how long did the engine sit after the rebuild before you fired it? (I use moly paste on the cam lubes now rather than the red crap...doesn't drip off)

Did it fire up right away?

Cam guys will tell you a new cam can be wiped out before the engine even starts if you crank on it for awhile. Best to prime the engine just before you fire it.

Any pics?

There have been alot of write ups about the oil and new cams going bad. Pros can and do have the same problems.

slagburn

Initial fire was done with diesel oil with a full bottle of GM EOS. It ran for 20 minutes at around 2500 rpm. Changed the oil to Brad Penn race oil immediately. Pressures were excellent at all times. I saw no recent drop in oil pressure when parts started failing. The engine was primed immediately before firing, and it fired within 5 crank revolutions. Keep in mind this is not a cam lobe issue, they are fine, as are the journals. The engine block is back at the machine shop and they are scratching their heads too.

ironman_gq

I think these engines use the lifter galleys to oil the crank as well so the lifters and cam see the oil first. If metal was in the oil from the gears then it would go through the cam bearings first and get embedded in the bearing metal and eat the bearings up but possibly not get pushed downstream to the crank bearings.

slagburn

I could see that on one journal maybe- but all of them? All cam bearings were damaged, the front 3 literally had slivers of metal hanging out while the back two weren't as bad. Possibly because of the valley oil line bypass.

slagburn

So today I reassembled the engine. The rear cam plug is out right now, but the rest of the oiling system is there. I hooked up my 1/2 air drill to an old distributor to check out the oiling. Now I am getting a steady stream out of the distributor drive gear on the camshaft, that's good. The lifters are all oiling, oil out the pushrods, etc. However, watching the rear cam bearing, I am not seeing any oil at all oozing out of there. It's got some sticky lube on the cam bearings, maybe that's stopping the trickle I'm looking for? Insight?

AMX69PHATTY

Obvious question, oil holes in the cam bearings lined up with oil holes in the block ???

jeep_man_401

I would hope you brushed all the oil lines with a rod and then physically see light on the other end of the hole. Short of a blockage or lack there of by the rear cam plug off...you shouldn't wipe out the cam bearings. I can see maybe if you didn't reprime the motor AFTER putting on the rear cam plug. Otherwise the pump would have to fill up that void before oil pressure is see on the cam bearings again. On a new engine? Stranger things can happen.

slagburn

Yeah, the holes are all lined up- all passages verified clear, everything's been brushed out, tanked, cleaned again etc. I can see how a new, tight bearing with sticky assembly lube being run by a low rpm air drill might not show any oil movement, I just want to make sure. The front of the motor, oil really runs out at the cam sprocket and through the cam gear holes, but then it has a groove in the front cam journal and another one to match in the bearing, so that's quite the large oil path there.

ironman_gq

how fast is your drill spinning? I would look for at least 600rpm on the drill and you should be able to feel it build pressure with the cam plug in. It should slow down the drill considerably.