I rebuilt my '92 Bronco 351W about 50,000 miles ago. Last week it suddenly started running rough, with an accompanying TAP TAP TAP TAP TAP TAP.

Oh-oh.

I have an old Snap-On Counselor II scope, so I plugged her in and did a cylinder balance test and a vacuum waveform. Sure enough, #6 and #7 looked damn near dead. I yanked the driver's side valve cover off and saw right away that the #6 exhaust rocker was flopping around with about 1/4" of lash. #7 & #8 exhaust were also a little loose. I pulled the intake and started poking around. Weird thing was that the #6 lifter plunger was just stuck, with no visible damage. #7 was badly dished, and had stopped rotating at some point, so it was worn off at an angle. #8 was dished, but it wore evenly. I pulled all the other lifters and they looked good.

What I did next wasn't real smart, since I suspected the cam was wasted, but I was hoping to get lucky since I thought I caught the problem right away before the damage spread. Besides, I was supposed to go on vacation this week and I needed the rig to tow my boat, and I was working on it in my employer's shop, so I didn't have a lot of time before he yelled at me to get it out of there. So I was kinda forced into taking a short cut.
I bought a new set of lifters, slapped them in, spun the oil pump with a drill to check for flow at all the lifters, buttoned the rest of it up and started it. I held the RPMs at 1500+ for about 20 minutes to break in the new lifters. About a minute after I dropped it down to an idle, it started the same crap again. WHACK WHACK WHACK WHACK WHACK with a bad miss.

OK, I took a chance, and I wasn't surprised it didn't work out. But what happened next was really a bummer.
I put it in gear to back it out of the shop, and when the RPMs dropped down to 650 or so, the oil pressure disappeared. Zippo. I put it back in neutral, and the oil pressure came back. I revved it up for a few seconds, the pressure held, but when I let off the throttle the pressure went away again when it returned to idle. I was thinking the stock sending unit might be playing games, but then the engine started sounding like a spoon caught in a garbage disposal and misfiring all over the place from the lifters bleeding off.
Oops. Guess I better shut 'er off.

I started it a couple more times, the pressure came back again, and as long as I didn't goose the throttle way up and let it fall back to idle real fast, it stayed good.

So yesterday I tore it down again, and this time I pulled the cam. It's wasted on quite a few lobes, but the journals look good. Just the half hour of running time hammered about six new lifters, including on the other bank where the old ones were still good. I can probably write that off to the previously damaged cam, but the oil pressure thing has me worried. I didn't have any pressure issues when it first went flat. I talked to the machine shop that did my block work, and he thinks the particulate from the cam wear got into the main/rod bearings and damaged them, but I'm not so sure. But on the other hand, I've never heard of a flat cam causing an oil pressure loss. Worn cam bearings will bleed oil off like nobody's business, but that would be a steady loss, not an intermittent "50 lbs one second and zero the next" kinda thing. I felt around inside the oil pan as best I could with the timing cover off, but all I found was clean oil, and no grit or anything else. I spun the oil pump again, and oil was flowing where it should be.

So now a dilemma; I don't want to yank the engine out just to look at the main and rods, since I don't think they're a problem. I didn't really mind wasting $50 and a few hours on a new set of lifters, but it's gonna be a couple hundred $$ and a whole day's work wasted if I eat another camshaft due to lack of lubrication.

Any ideas from the small block types out there??

 

There has been lots of problems with this, did you use diesel oil or a break in additave when you did the inital break in. Oil now days are not good enough for break in because, I belive, its zink has been eliminated. If not it will cause lobes to flatten. But normally it will happen befor 50k miles.

 

tear it down my friend, sorry but the rest of the motor is full of metal...I have seen it a few times where the motor had a ton of run time because it went un-noticed...(thats why I like solid lifter cams)

I think you will find as I have the bearings are waisted.....they will have grooves worn in them right where the oil comes thru the bearing, like it had sand in the oil.

Time for a rebuild......it's no ones fault..it happens.

do a search for camsaft brake in............

 

Did you put the cam grease on when you installed it? The initial start up is hard on all the motor internals, Liberal assembly lube and cam break in grease. And it is always best to try and put it together as soon possible so the assembly lube doesn't run off the components. When I redo a motor (full rebuild or cam, etc.) I always change the oil after about the first 45min then again after two hours, Diesel oil is cheap if you buy it by the case(gals) Cut up that oil filter you have on there now and see how much metal is in it that will give you an idea of what was circulating in the oil!!!

 

i prime my engine for bout an hour turning it every five min never had a prob

 

Ditto, the rest of the engine's going to be toast as well as the cam. Loss of pressure was likely the holes worn in the lifter bottoms from riding on the flat cam lobes. As Hemi's said, the rest of the engine bearings are going to be full of metal, ditto for the oilpump. There's no quick easy fix for this.

 

I once bought a 78 caprice classic(yes I know traitor!!) for $45.00!! There were 4 lobes on the cam were ground to just a round profile a couple of bent pushrods. I bought a new cam 4 lifters and 4 pushrods and a timing chain and a couple gallons of 15w40ci oil. I drove it around for 2 months then sold it for $1500.00 and I still see it running around town of course now its got 20" rims and a crazy paint job!!! It is the zinc in the oil that helps with metal to metal contact points! as well as phosphorous 15w40 without the energy conserving seal is the best bet for break in on any motor internals. They took out the zinc and phosphorous because it's not good for catalytic convertors on most SI rated oils!!!

 

some times you can get lucky

if the motor is already showing signs of pressure drop then it's likely the inturnals are damaged. if it still had good psi then i would just replace the cam and lifters and run it.

 

So diesel oil still has zinc in it? I use Shell Rotella in my 351 and thats what I'll be using for my 393.

 

The Rotella-(T) has it, thats what I run in all my stuff 15-40 I get it free at work. I use it in everything we have at work from the new F650 with the Cat motor to 5hp Honda motors. Never had a problem with it.

 

Yeah thats what I've been using. Going on 205,000 now and still runs pretty good.

 

The new CJ-4 oils have less zinc, But they supposedly will protect just as good!
The main thing that is good for a fresh rebuild is the lack of friction modifiers in diesel oils(the energy conserving part) They(Fric mods)will not let the motor wear in right and leading to more fling off of components in the long term(=less lube where you need it) If it says it meets ILSAC put it back on the shelf! The way c rated oils hold onto dirt and other contaminents is what you want so it carries it to the filter and can be removed. I generally use the cheapest diesel oil (15w40) I can find and have run it in my bronco since I bought it 8 years ago, and I change the oil around 5000 miles but I have definately gone longer with it with out a worry. Pulling off a valve cover is all the proof I need after sitting overnight there is still a sheen all over and it is clean no deposits whatsoever or sludge!! Of course there are trade offs!, Zinc from ring and valve seat blowby will foul out a catalytic convertor, If you have one that is!!! and the ash potential is higher which can lead to combustion area deposits leading to pre ignition but a couple of well placed ounces of water will take care of that!! Or some PB blaster in the spark plug holes, let it soak for a while, start and bring it up to 2000 rpm and it will peel it off(don't do this with catalytic converters!) My bronco has 300,000 plus miles and still going strong!! So I will stick with what has been working! When I change my plugs hopefully soon and if this thread is still around I'll post my compression numbers. If you have a fourwheeler or motorcycle run 15w40 in it and it will live a long life and you will not have a slipping clutch like you will get with ILSAC oils!

 

I used the break-in lube that came with the cam when I rebuilt it 3 years ago. I didn't really like the look of the stuff. It was too runny, and it looked like it didn't want to stay where it belonged. I ran straight 30W for about 500 miles, then switched to Mobil1 synthetic.

I bought a new Crane cam, and their break-in lube looks more like a paste or grease than a thick oil. I bought some extra just to be sure I have enough.

I pulled the engine last night, but the pan isn't off yet. I'll know more about internal injuries later.

 

Too much lube can be as bad as not enough------be warned. I only apply the stuff to the lifter bottom and cam lobe, and then only a thin film. I then flood the lifter valley with breakin oil. The lobe needs to get enough traction on the lifter bottom to set it to spinning on initial fireup. The oil splash will take over by then. No spin = sure death for both the lifter and cam lobe. To be sure, run it with the valve covers off so you can watch the pushrods to make sure they're spinning. If they're spinning, the lifters are as well. I'd steer clear of synthetic oil too.

 

I put a line of white paint on the push rods....well some times......

I helped my friend rebuild a 557 after a bad cam, the cam had like 5 lobes completely gone...truck never sounded right when I heard it for the first time..... anyways we got it apart and the crank was juck it had groves worn right at the oil holes like it had sand pumped thru it. he ended up getting a new block and all new inturnals, saved the heads....

The one thing a always do on any of my motors is ,if a hydo flat tappet with adjustale valve train or a solid flat tappet is mark the rocker nuts after i set the preload. I brake in the cam and re-set the rockers. If I get one that has to be adjust way more then the original mark i put on it I run it with the valve cover off and make sure the push rod is turning. I also check the adjustment a few time in the first 3000 miles. if the cam is ok and everything is right the marks I put on the adjusting nut stay right on the 12:00 position where i marked them. It's a lot of work but if the cams goes bad it might take 10000 miles before you will notice it because sometime! it takes that long to wear the lifter enough to lose all the preload in the lifter. Once the lifter has no more preload in it the rocker starts to tic and you just drove all that way with metal in the oil...

Ok i'm done......Good luck. Glad you are taking the time to check out the rest of the motor....