New lifters/old cam

I have been living with my intermittent clapped out lifters for a few years now, but it's time to finally bite the bullet and address the problem since they are sounding off nearly all the time at highway speeds now, whereas before I would only get intermittent clatter at idle and occasionally at highway speeds for a few seconds.

Anyways, I know (from searching!!!) that most people say you CAN use new lifters with an old cam, but what if the cam is starting to wear/already worn, what is the worse that will happen once I swap in new lifters? Some posts I found talked about flaking of the cam or something, what is that exactly?

I need to drive this thing around 600 miles over the mountains soon and I can't risk catastrophic failure at the side of the highway with the lifters the way they are (and catastrophic failure DOES seems imminent at the moment), but what about swapping new ones in? I know the cam is probably getting a little long in the tooth, but it still run's like a raped ape these days and has plenty of power...If I replace the lifters and it stops clattering I'd be a happy camper for as many years as I keep it for.

Any insight? Oh, and happy new years...the JEEP just wished me mine with this bit of bad news!

Year, motor, details, etc. please

1990 renix 4.0, approx 110k miles. Did the RMS 2 years ago @ around 100k when I bought it and the main bearings all looked good, but there were lotsa hard chunks of what I assumed to be carbon deposits of some sort in the bottom of the oil pan. Cleaned it all up, cleaned the oil pickup screen (was pretty clogged), put it back together and have put around 10k miles on it since then. Oil pressure is within factory specs, typically run 15w40 but have tried just about every viscosity on the market to see what would happen with the lifters, seemed to like the thicker stuff better. Have also tried ATF in the crankcase, Rislone, MMO and a host of other additives to not much avail.

The lifter noise was intermittent at the time of the RMS but started to get worse after a few months of driving (the jeep sat for a year or so before I bought it and before that was driven very short distances with a bad thermostat by the previous owner, so basically it never got up to operating temp).

At the moment I use around 1/2 quart of oil per change through various small leaks, doesn't seem to burn any oil at all though.

Using new lifters on an old camshaft is perfectly acceptable.

Since you always put new lifters on a new cam; you'll have to replace the cam if it fails anyhow. However, the cam won't fail just because you've put new lifters on it (although you should follow engine break-in procedures anyhow when you replace lifters - they need to "scuff" into place on the lobes.)

"Cam flaking" would be where some bits of the cam lobe break off at the edges - since you don't ride on the edge, it's not that big of a problem. Look at the cam lobe, and divide into fourths from side to side.

Now look at it carefully - you'll see there's a slight taper to the lobe (it's there to help the lifters spin.) You'll be running your lifter against the "third fourth" of the cam lobe, counting from the low side (it's a difference of about .003" - I'd be surprised if you could see it just by looking. Exaggerate with a straightedge.)

How does the lifter spin in its bore? Now that we're done looking at the cam lobe, take a look at the lifter foot. Take a known straight edge or flat surface, and set the lifter on its foot on there. Now, rest your fingertip on the head of the lifter and you'll find you can rock it about slightly - the "flat" foot isn't really flat (it's a circle with a ~30" radius.)

The action of that slight crown against the slight taper of the cam lobe are what spins the lifter, and what keeps the lifter foot from getting worn through by the cam (if the lifter stops spinning, the lifter will usually fail first.)

If you carefully inspect the lifter foot, you should see a sort of "square" polished spot more or less on centre - this is the wear pattern we're talking about (it's the contact patch between the lifter foot and cam lobe.) If you carefully inspect the cam lobe, you'll see a polished band around the lobe - same thing. You don't use the entire lobe or entire foot to make contact. You may need magnification - ten to fifteen times should do - to see the polished detail.

When putting in the new lifters, make sure you are generous with the assembly lube. "Too much is almost enough." Don't worry - engine assembly lubes are oil-soluble, and will flush away later. Here's what happens:

1) The engine turns, and the assembly lube provides initial lubrication.
2) The oil begins to circulate, and begins to gradually flush the assembly lube away (the assembly lube enhances the lubricity of the oil until it is flushed away.)
3) The assembly lube remains in the engine oil until it is changed, so your startup oil on a fresh build is enhanced by the assembly lube.
4) The assembly lube is flushed away with the first oil change (you don't need it anymore anyhow.)

How would the noisy lifters fail? And you do have to R&R the head to replace them don't you? Are you sure you have good enough oil supply to the head?

winterbeater said:

How would the noisy lifters fail? And you do have to R&R the head to replace them don't you? Are you sure you have good enough oil supply to the head?

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Lifters tend to either "collapse" or "go flat" (they don't retain enough oil pressure to maintain lash adjustment) or "go solid" (they don't "pump down," and valves never quite close.)

Yes, you have to R&R the head for service.

The lifters supply oil to the head, not the other way around. Oil under pressure is supplied to the lifters by an oil galley, the lifters "pump down" slightly when they open the valve - this "pumped" oil travels up the pushrod to the rocker arm, the other tip (at the valve) is splash-lubricated; and the oil dribbles down the head, drains back to the lifter side, and runs down (under gravity) around the lifters and back down to the sump.

Thanks. 5-90. You see so many forum responses that are total crap, but I know that you always have the answer I can believe. This Jeep forum though is way better than the Crown Vic forum I also visit for answers on my vehicles.

Thanks for taking the time to explain all that to me 5-90, I've learnt alot about my jeep from you since I started using the message board.
sounds good, I'm going to freshen up the motor by doing the lifters, timing chain, waterpump etc. While I'm at it I'll take the head to a shop to get it pressure tested and a valve job. I'm also thinking that I'll pull the oil pan again and clean out any sludge and make sure the oil pump pickup screen is clear again.
Anything else I should do while I'm in there?

Front and rear mains - you're there anyhow. You can do the front main on the bench (you'll have the timing cover off,) making that easier - the rear main can be done without having to pull the transmission or crank, as it's a metal-cored two-piece seal. Be sure to check the sealing surfaces of the crank for grooves - if you didn't have a leak before, you're not likely to find one, but it's good practise.

I did the RMS a few years ago, and I don't lose any oil from there 2 years later but I'll definately do the FMS, hadn't thought of that. Thanks again!

Oh, and if things have been running well for the last 2 years would you even bother getting the head pressure tested and all that? I'm in a pretty small town visiting my folks while this started happening, so turn around time could be a little while for a pressure test and vavle job. Luckily I have access to a retired mechanics shop space while I'm here, but I have a timeline to get back home and can't push it too far.

clunk said:

I did the RMS a few years ago, and I don't lose any oil from there 2 years later but I'll definately do the FMS, hadn't thought of that. Thanks again!

Oh, and if things have been running well for the last 2 years would you even bother getting the head pressure tested and all that? I'm in a pretty small town visiting my folks while this started happening, so turn around time could be a little while for a pressure test and vavle job. Luckily I have access to a retired mechanics shop space while I'm here, but I have a timeline to get back home and can't push it too far.

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If you have the oil pan off anyways I'd throw an oil pump in there, a one peice oil pan and valve cover gasket would be on my list as well. You'll thank yourself later! Is there somewhere you can have the head machined in town? A good time to install valve seals too

The oil pressure is measured at (near the filter). The oil then goes to the mains (etc.) then up. Any sort of blockage or excessive bleed off, should show up as little or no oil to the rocker eventually. Oil pressure isn't everything, oil volume to the top of the motor is also relevant. Face it, the 4.0 isn't a tight motor, things in general can be way loose and still run fine.
After cleaning out the top and bottom of my motor, I had some high pressure issues (higher pressure than expected). Likely it was a partial blockage in one of the oil up passages. It eventually cleared itself, but the nasty lifter racket at startup and occasional tick while running was annoying.
IMO collapsed or tired lifters, is fairly low on my list of probable causes, much more likely to be excessive oil bleeding off lower in the system (connecting rods??) or a partial blockage someplace.

clunk said:

I did the RMS a few years ago, and I don't lose any oil from there 2 years later but I'll definately do the FMS, hadn't thought of that. Thanks again!

Oh, and if things have been running well for the last 2 years would you even bother getting the head pressure tested and all that? I'm in a pretty small town visiting my folks while this started happening, so turn around time could be a little while for a pressure test and vavle job. Luckily I have access to a retired mechanics shop space while I'm here, but I have a timeline to get back home and can't push it too far.

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Having the head pressure-tested is something you only need to do if you already suspect a crack, have done a leakdown test, and can't figure out where the leak is that way. If it's been running fine, you don't need it.

If you haven't overheated the engine, it's not likely that your heat will be warped, either. Doesn't mean you shouldn't check (it's easy enough to do, if you have a "known good" straightedge and a set of feeler gages available,) but you'd have no reason to suspect it. Head warpage is not a contributing factor to tappet noise, in any case.

I'd like to suggest something - if you haven't already started the work. Get the stuff on the top end first, before you even drain the sump. This will allow you to clean the top end and get all of the crap in the oil, which will then drain out before you pull the sump. Then pull the sump and scrape that out (I find that the plastic scrapers you usually find in the paint department at the hardware store work quite well for this sort of thing.)

What about retorquing the mains and con rod bearings. I always figure it never hurts to check 'em all out while the pan is off. Not loosening them or anything, just verify that they're all still tight to torque specs. When I did that on my '79 Mustang with 30K miles on it (25+ years ago), I was shocked that some were getting (or maybe always were) loose.

8Mud said:

IMO collapsed or tired lifters, is fairly low on my list of probable causes, much more likely to be excessive oil bleeding off lower in the system (connecting rods??) or a partial blockage someplace.

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this is actually something that's playing in the back of my mind as well, and I'm secretly pretty worried that I'll do the lifters and everything and still have the racket because of a blockage somewhere. All the hardened carbon junk I cleaned out of the oil pan definately could have clogged something up.

clunk said:

this is actually something that's playing in the back of my mind as well, and I'm secretly pretty worried that I'll do the lifters and everything and still have the racket because of a blockage somewhere. All the hardened carbon junk I cleaned out of the oil pan definately could have clogged something up.

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It's a pain, but not all that bad, to pull the valve cover and see how much oil is flowing (being pumped) to the top of the rockers.
I've been trying to find a good oiling diagram for the 4.0 forever with little success. I have a couple of oiling diagrams that are poor to useless.
I'd pull a couple of rockers and turn them over to see just how worn they are, I've seen 4.2 rockers that were worn most all the way through. You can get a decent idea of the looseness and wear by running each cylinder up to TDC and just wiggling the rockers. Especially if you've been in a motor before and have a little feel for what is acceptable and what is excessive, they will have a little slop (or side wiggle) normally at TDC.

Okay, thanks. I actually had the valve cover off around a year ago to check them, and they all seemed uniformly even when I checked the play. I didn't have a torque wrench available at the time so I could not check the tightness of the rockers. I'm going to pull the valve cover again today and pull a few rockers out to check for wear like you suggested, I have an idea of which lifters are going bad so I should be able to check those rockers first to get a good idea.

clunk said:

Okay, thanks. I actually had the valve cover off around a year ago to check them, and they all seemed uniformly even when I checked the play. I didn't have a torque wrench available at the time so I could not check the tightness of the rockers. I'm going to pull the valve cover again today and pull a few rockers out to check for wear like you suggested, I have an idea of which lifters are going bad so I should be able to check those rockers first to get a good idea.

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Meh - if you've got to replace one tappet, just do them all. Especially on the 242ci, where you have to rip the head off to get to them in the first place!

Make sure the bores are clean, and be generous with assembly lube (use about twice as much as you think you need, and then a bit more. You're not going to hurt anything by doing it that way...)

Bear in mind that the screws for the rocker pivots are simply torqued to spec (19 pound-feet? I'd have to check - if I have it, it's up on my site...) and it's best to torque them at TDC with the valves CLOSED. The remainder of preload adjustment is handled by the hydraulic action of the tappets themselves.