Diagnosing and Repairing Your Imperial's Valvetrain


Imperial Home Page -> Repair -> Engine -> Valvetrain

Question from Bill:

How hard is it to do a valve job?


From Dave:

You might want to replace the valve guides & seats with a harden type of parts etc. This will enable less top end wear due to unleaded fuels of today. However this is a specialist job.

From Steve:

Valve job on the car would be difficult for you to do on your car, mostly because you don't really have a place to work on it. You have to pull the heads off the car to do it and this requires being able to work under the car and beside the car for many hours (If I remember correctly you have only one cramped parking spot to work in?)

I also would advise you not to do just the valve job. There is a good chance that if you rebuild the top half of the engine you will start burning oil due to extra stress being placed on your rings. Many people do it and get away with it, but if you aren't one of the lucky ones then you end up doing all that hard work over again.

From Kerry:

I'd also agree that building just the valves can cause the motor to start smoking as the compression will increase but the old rings will not be able to hold it.

Pulling the heads on a 413 is not that difficult but might be a bit much for a novice.

From Kenyon:

Jump in and do it as a novice, but be prepared to learn, and maybe learn the hard way. Getting a little help during the process from someone that's already been there could make all the difference in the world.

"Doing" a valve job is probably several rungs up the ladder from novice. The parts involved are a lot more brutish than the little carb parts that you dealt with on the last round, but there are a number of ways to do things incorrectly if attention to detail is not paid.

You didn't mention why the valve job was needed, and I'll assume that you have your reasons. If you're not sure, one thing that you can do is a compression test. There is a tool with a brass threaded fitting at one end and a dial gauge at the other end of a soft hose that threads into the spark-plug hole (you do one, by one, cranking the engine and then writing down each cylinder's value and then replacing spark plugs as you go to each cylinder).

This page for a 1960 413 engine shows the firing order and lots of other helpful reference items. The compression tolerances are there, too, and can give you an idea how far away from stock your engine is once you take your reading. The numbering of the cylinders and firing order is there too, for when you need to explain to the machinist which cylinder is bad and which spark-plug wire goes where if you don't label them ahead of time....

Using one of these compression gauges on a V8 that I had that was lumpy led to me figuring out that #8 cylinder was the one that was bad, and it got special inspection when things came apart. Turned out to be both a fried valve and a bad cam lobe.

Engines have a "top" and "bottom" end. The heads that contain the valves are the top. The cam is sort-of in the middle, as it is located in the block, but since it operates the valves, a cam that has worn and is "flat" can fail to open one or more or all valves all the way, directly affecting the "top" end.

To strictly answer your question about what's involved in a valve job: The intake manifold that the carb sits on is unbolted from the engine and lifted out. The exhaust manifolds are removed, laying the exhaust aside in the engine compartment. The valve covers come off, revealing nuts or bolts that when loosened, allow you to lift the heads off. I fell into owning the tool that takes the valves out of the heads by compressing their springs, but I doubt that I'll ever use it. I'd just take the whole head over to the machinist. When he's done, you'll have heads that are ready to bolt back onto your engine with a fresh "valve job" done at the machine shop for you. You'll need a bunch of gaskets, so ask what you need before going home with your newly redone heads.

OK: You took your heads off and are re-doing the valves. Had you done the compression test, you'd know how closely grouped the cylinders are to each other and how far away from stock measurements they are. If one or more are significantly low, is the valve really the culprit? Is the cam lobe that actuates that valve not doing its job due to wear? Are the piston rings still sealing correctly (or broken?)? All three work together to create compression and the cam is supposed to hold the valve open far enough, long enough to allow the cylinder to draw its breath into the combustion chamber during the cycle.

You'll doubtless get other opinions about the technical details on your valve question and the merits of doing just that procedure in other emails, but I'd be inclined to do the entire engine all at once if you have the money. Doing the heads and refreshing the seals on the valves and then mating the newly redone heads to the used and broken-in engine could create more stress on the lower-end, as well as more blow-by where the rings don't seal like new (but the valves do) and gas gets past them during the compression stroke (this is called "blow-by" by some). Blow-by's consequence is removing oil from the cylinders and accelerating cylinder wear and gas getting into the oil in the pan in the process in a worst-case scenario.

The "bottom end" of the engine is the crank, the piston rings/pistons, connecting rods, and all of the bearings in there. Fresh valves mean that you could accelerate the wear via less leakage at the valves/higher compression pressure and create a situation where the already used engine gives out at some sooner point in the future due to higher compression forces, after all of this work that you just did on the upper end. You'd have to pull all of that work partially apart to redo the bottom end at that point anyway. I'd rather wrench once and drive than re-wrench later if avoidable.

The other side of the coin here is that the V8's are plenty beefy, you just want to freshen things up, and what the heck, you'll rebuild later if needed - you just need to solve a problem in the valve-train for right now. Don't get sore if other things need attention sooner or later due to the fact that the engine's been around the block already and worn together. Upsetting that "worn together" balance can unmask other items that are worn and then cause a progression of frustrating failures that are neatly escaped in a complete engine rebuild the first time around.

I'd suggest doing very thorough investigation of your options and their consequences so that you can weigh things properly and know what to expect out of your proposed maintenance. If you've never seen what's under the intake manifold and how an engine works, it's a really revealing experience that will put all of the vocabulary that you've heard into perspective, so that's a good aspect to doing this yourself.

If you haven't been through this before and proceed, be certain to read the FSM carefully and to ask advice from people, especially your machinist, as you proceed. Extra points if you can lift the hood and have someone point to what each step will involve. It CAN be done by you. I'd suggest having a buddy along who has done it before and might be able to point out some of the things that aren't obvious till you go there, like the fact that when reinstalling your heads, there is a torquing sequence laid out in the manual that you should go by when tightening down the bolts that hold the heads on to avoid warping the head as it is tightened down.

Not a complete story, but I hope that this helps give a better picture of the road ahead on doing your own valve job.

Question from Ken:

We have discussed the identification of valve tappet noises as compared to exhaust leak noises. I have identified mine as valve tappet. Now I have question for your 413/440 experts out there. If one has a noisy tappet and one doesn't fix it right away, does one damage the engine or valve train? I know it needs to be fixed but if it isn't hurting anything I would like to put it off for a while. I have tried the magic stuff in the can (which I have had success with on other cars) but to no avail. I recall fixing a really stuck lifter once in one of my 57 Imperials by adding a quart of transmission fluid to the crankcase. Fixed it in about ten minutes and I never had a problem again. I haven't tried that yet on this one but am tempted.

Reply from Brian:

First of all, what weight of motor oil are you using. 30 weight or 10w30 is too thin for these old cars. Put a quart of tranny fluid in it and run it for a few days this way. If it helps, change the oil and use 20w50, unless you are in a cold climate. If this does not get rid of your problem, then park it until you can fix it. It will take some time, but if run this way, it can bend pushrods, break, or wear rocker arms severely. Many times when one of these things break, they take other things with them. If the tranny oil and thicker oil help, make sure that you change the oil often, as lack of oil changes and sitting for long periods of time is what creates this problem.

Question from Remco (392):

My 392 is smoking lika a steam train I think the small rubber caps that are on the valve stems are gone. Can I replace these without having to remove the cylinder head?


From Julian:

White smoke is coolant, blue is oil and black is gas.

From Demetrios:

If its the valve stem seals, usually the car smokes a lot at startup. Also, in the summer, the condition is usually aggrevated.

I have heard that by pumping compressed air in the cylinder, you can prevent the valves from falling when you remove the springs and retainer. If so, you can replace the stems with the heads on. I can't see why this cannot apply for a 392.

Follow-up from Michael:

This isn't really conclusive and probably more often is a sign of worn rings. The usual manifestation is that the engine starts up ok, but as soon as the RPM is raised much above idle, the smoke starts rolling out, the reason being that the cold, worn rings are unable to seal against the oil sprayed on the cylinder walls when the engine speed is raised. The smoke tends to subside to some degree as the engine warms up and the rings and piston expand into the cylinder. A somewhat better quick check of the valve stem seals is to drive the car until the engine is warmed up, then let it idle for a fairly long period, say 3-4 minutes. This challenges the stem seals with high intake manifold vacuum, but does not tax the rings so much since there is relatively little oil being applied to the cylinder walls at idle. Now step smartly on the gas and drive away. If you are being followed by a smokescreen worthy of James Bond, it's a safe bet the valve stem seals are shot. Remember that all these external check are just indicators, and that often, the stem seals and piston rings are BOTH worn

From Kerry:

The air tool that hold the valves up works great. I've done this procedure on several cars.

However, before you go to this trouble, make sure it's the valve seals. If the smoke is worse at start up and goes away, it is probably the valve stem seals. New ones will help. If it smokes all the time, it's probably something else. Smoke color will tell you what. Black is fuel, blue is oil, white is water. If it smokes blue all the time, you have oil rings worn or broken. Probably worn out. Compression checks will give you a clue as to the state of the engine as USUALLY worn oil rings are accompanied by worn compression rings with corresponding lower compression.

From DeVere:

Yes, there is a handheld tool that will compress the valve spring so you can get the "keepers" out to remove the spring and seal. You will need to have the piston at top dead center, and compressed air bleed into the cylinder from the spark plug hole or a piece of rope stuffed in the cylinder to keep the valve from falling into the cylinder while you work on it. Remember to remove any burrs or "mushrooming" on the end of the valve stem to not tear up your new seals. The tool grabs the lower part of the valve spring, has a hand wheel you turn to compress the spring and will keep it compressed while you remove it. You must be sure the piston is exactly at top dead center, or the compressed air will push it down, you do not need a lot of P. S. I. of air, just keep the valve from falling. (65 Imperial). (afterthought, if the valve rockers are off, and the whole side would be, you do not need the piston at t. d. c. it will not matter, just watch the fan, if the air moves the piston, and turns it quickly to the bottom.)

Question from Terry (flathead engine):

Started my car the other day and would swear its running on two cylinders.  Not run often. Took it to Detroit in trailer a couple of years back and it seemed to start missing on one cylinder to me and then quit. Wondered if a valve was sticking.  Drove it a little around here probably once after returning and was still missing on occasion.  Put probably a quart of Marvel Mystery oil in to help cut corrosion if that was the case and ran it a while with no real noticeable change. Parked since then till now.  It would run but it's very weak and backfiring through the carburetor on occasion and I could see gasses coming up through carburetor with AC off while running.  Engine making a few clanking sounds like valves hitting to me.  Any hope of dumping some sort of solvent in or should I just give up and open it up. Was a Sears and Roebuck rebuilt engine when I got car in1970--probably only 5,000 miles ago.  Could old gas be gumming things up??  

Reply from Dick:

Your 50 very likely has the valve stems seized up in the valve guides. This is a common problem of fresh rebuilt engines that are parked before they are completely broken in, and then only run for short distances. Flatheads are especially prone, since the fuel that seeps down into the guides turns to gum, thus preventing the valves from closing.  As you can see, this would happen only to the intake valves, usually.  Thus the popping back through the carburetor.  Don't try to fix this with "mechanic in a bottle" cures, they never work.  Also, don't run the engine any more, you are punishing the camshaft bearings with the metal to metal contact when the cam tries to move the valve stems.  Fortunately, the pistons are not bumping the valves back down on this engine, so you have done no real damage so far, if you haven't run it too long.  

What you have to do is to remove the head and the inner fender on the passenger's side, then pull the valve covers off the engine, and then disconnect and remove all the intake valves.  Keep track of which one was in which hole! These will probably be stuck really fast, you'll have to be careful not to damage the valves when pulling them. Try just soaking the valve guide area from the top with carburetor cleaner or acetone (don't get it on the paint!!) while you attempt to twist and pull on the valves. When you get the 6 intakes out, crank the engine over and watch to make sure that the exhaust valves are not sticking too.  Probably they are OK. If not, you know what to do!  

Now, get some more carburetor cleaner and go to work on those guides. You'll probably need to chuck up a small piece of cloth in a monster cotter pin into your 1/4 inch drill motor, soak the cloth in the solvent, and then run the contraption up and down 143 times in each guide until you feel they are coming out clean. Put lint free rags in the valve lifter area to keep the solvent from running down into the crankcase through the drain holes.  (Lint free rags are available as "bar wipes" at most restaurant supply outfits, and also at "Trader Joe's" out here in the west. Run then through the washer one time before you use them to get any manufacturing dust or > threads off them.)  

Now, clean off the valve stems and try them one by one, in their proper hole. With engine oil on each valve stem, they should move smoothly up and down in the guides without sticking. Rotate them to be sure. Keep trying both cleaning methods until you are satisfied everything is clean.  If you can't get there, perhaps the guides are too tight.  I hate to mention this, but the easy way to open up a guide is to chuck up a piece of crocus cloth, very fine grade, in your spindle (cotter pin as mentioned above) and hone the guides with it. I caution you, this is a last resort, as you are taking away metal that will reduce the life of the valve job, but sometimes there is no other way to get the valves to quit sticking. Of course you have to be scrupulously sure that none of the abrasive finds it's way into the crankcase! 

Don't get  carried away with this.  As soon as the lubricated valves will slide smoothly up and down with no "sticking points", and rotate freely in the guides, you're done. Put the engine back together and drive that puppy until you get some real miles on it! Don't ever just run it for 1/2 hour and think you've done it good.  If you start an engine, drive the car at least 10 miles - always a good rule! If you can't drive it 10 miles, it's better to just let it sit.

Question from Dan (1958):

Can anyone tell me what year Chrysler printed "IMPERIAL" on the valve covers of their Hemi engines?


From Denis:

The '58 Imperial came with a chrome plated version. They look soooo nice. First year, unless some 40's or '50's had it?

From Rodger:

Chrysler/Imperial had no valve covers prior to 1951.  On the side of the valve spring cover on the flat heads there was no stamped names or decals with names.

From Charlie:

All Imperials were flat heads until 1951 when the Hemi came out. Ergo, no valve covers.

From Muir:

From what I can gather, from '51 to '56 all Imperials had the firepower tappet covers, and '57 - '58 had the IMPERIAL, although these may have only been for '58. Also I think the standard covers were painted only - never plated, although in '60 there does appear to have been dealer only installations of chrome air cleaner and tappet covers - whether any earlier versions had this available is conjectures.

Question from Rex (1960):

I have an interesting situation with my 1960 Crown that I would like some feedback on. When I bought my car a over a month ago, I thought it might need a valve job to correct a skip. Well, this past week I finally went forward with it and had the heads removed and sent to the machine shop. I could see the suspect valve was burned somewhat.

However, I was shocked to stop by the machine shop and be told that the burned intake valve was actually the wrong size! It was smaller than the other intake valves and was seated much higher in the head than the others. When it was removed, it was obviously not the same size as the others. Now, I know beyond question that the heads have never been off this car, since I bought the car from the original family who carefully maintained the car. The motor on this car has never been touched. Can anyone comment on how this might have happened at the factory or has anyone seen anything like this before?

Reply from Dick:

Someone is pulling your leg - either the machine shop guy or the previous owner, but what you have been told and shown does not make sense. I'm certain no car was ever shipped from Detroit with the wrong valve in it.

But what does it matter? You need a valve job - have it done and drive in pride! The 413 is the most rewarding engine ever to come down the pike, in my opinion - prepare to be delighted!

Question from Jasmine (1965):

I was very sad to learn that I have a burnt exhaust valve on my '65. Can anyone give me an idea of what causes that, how to avoid it in the future, and a reasonable price I should expect to pay to have it fixed.


From David:

If it were me I would take the head off, both of them and put new valves in. My '66 started out with some burnt valves and got progressively worse. Proper timing and good gas will help avoiding this in the future.

From Paul:

It is not the end of the world. Take the heads off and have them both reconditioned with new hardened valves and valve seats. Then this will never happen again.

From Joachim:

I worked for many years in the 60's for an engine rebuilder in Ecuador, burnt valves also have to do with a TO LEAN fuel mixture, as this also tends to increase heat in the cylinders. In case of worn valve stems and/or guides in most cases our workshop would ream out the guide and fit valves with oversize stems when available. Sealed Power used to supply quiet a variety of valves with oversize stems, in most Chrysler applications they would be 0.005 - 0.010 and 0.015 oversize.

From William:

From the experiences with our Chryslers, at about 80,000 miles on a 1960-70s vintage B/RB V-8, you can expect to have a burnt valve. Seems like ours were usually on #5 or #7 cylinders.

First, some background information. When the rocker arm pushes down on the valve stem to open the valve, it exerts a sideways motion into the stem as it moves the valve open and then a similar opposite force as the valve closes. The rocker arm wipes across the top of the valve stem instead of just pushing straight down, so that is where the sideways motion comes from. This causes the stem and guide to wear where they contact each other. There is a clearance spec for the "stem to guide clearance" in the service manual. In extreme cases, this clearance can sound like a flat tappet solid lifter camshaft that need adjusting, from what some manuals say.

Now, as the stem wears against the machined valve guide area, the clearance will widen. When the clearance gets wide enough, it will let the valve wobble in the guide as it move up and down during the close-open-close cycle. This wobble and the sideways force exerted from the rocker arm will not let the valve squarely seat in its valve seat area of the cylinder heat. When it doesn't seat squarely for the combustion cycle, a small amount of hot gas can escape past the area it's not fully seated in. With time, this will erode the valve head and the valve seat and result in the "burnt" valve situation.

When the valve starts wobbling, it will also wear the valve stem seal and possibly result in more oil getting down into the guide area than is necessary, which might figure into the mix too, but usually this might not be a factor as it's usually the exhaust valve that has the issues so the extra oil goes out the exhaust pipe.

The fix? There are several from "just enough" to upgraded valve guides and valves.

The "just enough" would be to knurl the valve guide and put a new valve in the head to replace the burnt one. New OEM spec seals are usually in the cylinder head valve grind gasket set. Many times, only the head with the valve problem is worked on. This route probably costs the least.

From there, you can disassemble both heads, get them surfaced on a lathe for trueness and inspect all of the valves, check the springs for correct tension, check for cracks, and other things that you might desire to look at with everything apart. Then, you recondition the valve guides completely by machining them for bronze helicoil guide inserts. From what I've read, a bronze helicoil guide insert and a chrome stem valve make for a great interface with respect to long life.

In this situation, you put the heads on a drill press and tap the guides to install the bronze helicoil, just like a helicoil repair of a normal bolt hole in aluminum. After you thread the insert into the guide and fully seat it into the guide, then you trim the ends. Then, you insert a new valve and check for freeness in the guide.

Once the guide is reconditioned, then the work on the valve seats can progress. It has to be done in this order too--recondition valve guide and then recondition the seat.

There is also a "knock-in guide" variation too. Basically, the existing cast-in guide is machined to accept an interference fit valve guide insert, much like sleeving a cylinder wall. This would be in the most extreme cases, I suspect, but was more common in prior decades of the 1970s.

Using a knock-in guide tends to defeat one purpose of the integral valve guide. The knock-in guide is reputed to form an extra heat barrier between it and the cylinder head casting, which can delay the heat dissipation from the valve stem into the cooling system. Hence, the valve and guide run hotter.

Whether or not you also add hardened valve seat inserts to your heads when the valve guide operations are done is your judgment call.

When at the Buick Centennial Celebration last July, I attended a seminar by a retired Buick V-8 engine engineer. The question of unleaded fuel came up. He noted that when the GM "word" came down to use unleaded fuel, Buick did not immediately go to the induction hardened valve seats as other GM divisions did. He noted that as they were already using nickel steel valves, the hardened seats were not really necessary (according to their research). In a year or so, they did get on the induction hardened valve seat bandwagon, though.

On that note, the induction hardening is only a surface treatment. My machine shop operative advises that after the first valve job, it's ground away. But without it, Chrysler research indicated that normal seats and unleaded fuel, when used in the "max load" trailering activity, would destroy a cylinder head inside of 12,000 miles of such use. I saw that article in an "Automotive Industries" magazine in the early 1970s. But, we don't drive our older vehicles with massive trailers around the proving grounds continually at WOT, typically.

On valve seals, the OEM spec seals are fine. There is a orange silicone version that will work too (from a big block Chevy 454 application, but I think there might be a similar Chrysler supplied seal too). Key thing is to not get the guide too dry, oil wise. Some oil has to get past the seal for the guide to get sufficient lubrication, just not too much. In other words, NO Perfect Circle style "scraper" seals on a street engine for that very reason.

How much money you spend and how is your determination. Finding a competent machine shop can be a task too! Good guides that are the reference point for a good OEM spec valve job with at least OEM spec quality valves is probably the best defense against future burnt valves. Also figure a quality motor oil into the mix too.

Question from Steve (1968):

My '68 seems to have developed an appetite for pushrods... I straightened, then replaced a few, then started replacing lifters one-at-a time where pushrods kept getting bent, thinking the lifters may be sticking. This is a 44,000 mile car that sat in a barn from 1979 until almost 2000 when it came to live here.

Has anyone else been through this with a 440 that's sat a long time? I should probably just replace all the lifters, by the sound of it, but wonder if anyone else has some input?


From Dick:

It may not be the lifters; another good possibility is that the valves are sticking in the guides. To check this out, you'll need to pull the rocker shafts, then take the keepers off the valve stem to see how easily they slide in the guides. It is very common for engines that are left undriven, or driven on short trips only, for a sort of varnish to build up on the valve stems, making the valves seize up when the engine gets hot. The cure for this is to clean the stems and guides, but if you don't want to remove the heads, try soaking the valve stems with carburetor spray cleaner, then working the valves up and down a few times until the stems seem to be clean and slide easily in the guides.

If this doesn't seem likely to you, you can try running a detergent booster additive to your oil for a while to see if you can free up whatever is sticking in the lifters to make them pump up too high. The problem with bent pushrods is that this is a symptom which also tells you the valves have been driven into the piston tops, if the cause was pumped up lifters. At least in the case of the sticky guides, there is probably no damage to the valves or pistons - so hope for that!

From Joe:

Had a 383 that had ring seized last year.Add a quart of Marvel Mystery Oil to the oil and just let it idle for half an hour. I changed the oil and it's been running great ever since.The stuff is amazing!!!

From Chris:

The '70 Imperial Lebaron that I just purchased (and safely transported it 6 hours to its new home) had a similar problem from the last owner. A pushrod bent and a lifter popped out of it's bore causing oil pressure to cease in the engine. The engine was rebuilt; but, I think only the heads needed done. What I feel that cause the initial problem was the valve sticking in the valve guide causing the valve train to bind up resulting in a bent pushrod and lifter poping out. Now might be the best time in having the heads redone including hardend valve seats installed. This might be your best bet.

From Bill:

Several have mentioned the probability of a sticking valve stem causing the bent pushrods. I wanted to mention that it may be more cost effective when rebuilding heads to simply buy a reconditioned set from Aerohead in Indy. They advertise in some of the Mopar magazines a price of $499 for a pair, outright, of either big block or 360 heads, with an additional charge of $80 for adding hardened exhaust seats. Last summer I decided to rebuild the heads on my 340 Cuda and took them to the local machine shop. These are the '72 and up style 340/360 heads, not X or J. They skimmed the surfaces, installed new .500 lift valve springs, hardened exhaust seats, ground the valves (I needed 1 exhaust valve and 2 intakes), new exhaust guides, and added new umbrella seals, the total cost was nearly $800. The Aerohead deal also includes new valve springs capable of over .500 lift, and the other things named. I wouldn't have to consider shipping since I live about 50 miles from their shop, but shipping should be around $150 to the furthest reaches of
the lower 48 I would suspect, making a grand total of $730 or less. If one of your original heads has a crack anywhere, add $100 per crack for fixing them, that's what they charge in this area anyway. So it ends up looking pretty good. I haven't tried them myself yet, but I'm condering getting a set for my '65 Imperial, which really needs a valve job pretty soon. I might add the extra $100 to obtain 915 heads to retain the full compression ratio.

Question from Charles (413 and 440 interchange):

Will 440 valve covers work on a 1962 413. Or where can I get covers to fit?

Reply from Paul:

I think the number of mounting holes might be different, but the ones that are the same should line up.

This page last updated June 9, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club