How Do You Know If Your Imperial's Engine Needs To Be Rebuilt


Imperial Homepage -> Repair -> Engine -> Engine Rebuild

Tips from Rolland:

Check these before you spend the money to have your engine rebuilt:

1. Have the compression checked - if all cylinders are relatively even in compression pressure (25 PSI variation) and at least 125 PSI you can assume the valves are good. 

2. Does it smoke? This is an indication of worn rings.  If it consumes more oil than you can tolerate or smokes a lot from the tailpipe you may be in for a rebuild. 

3. Is the oil pressure good?  You should have at least 20 PSI idling with the engine warmed up and 50 PSI at road speed.  If this is low the engine bearings are probably worn. 

A poor running engine is not due to a worn out engine. If the valves are bad it will cause rough running and loss of some power but an engine can be extremely worn and still run well.  Unless you want perfection in the engine or you have a couple of thousand burning a hole in your pocket check the above items.

If your car has been in storage for a long time, it may result in stuck rings or damaged cylinder walls due to corrosion. Many times this will correct itself with some highway driving. After it has warmed up try running it for a distance (maybe 30 to 50 miles) to see if it improves. It will take longer than that to totally free up but you will get an indication. During this time it is not necessary to run at high speed but go to wide open throttle from say 30 mph to 60 mph without letting the transmission kick down. This will load the rings and help free them as well as let the cylinder walls clean up. Some oil additive such as Rislone in the oil may also help. If you don't see some improvement after 300 to 500 miles you may be in for a rebuild.

Tip from Norm:

A rough running engine can sometimes be traced to something as simple as old gas that has lost its volatility ( if the car has been sitting for a long time ). Try the simple things first: plugs, wires, points, cap, rotor, carburetor cleaning, fuel filter, etc. before you spend the money to have your engine rebuilt.

Question from Bruce:

Would a "weekend warrior" amateur mechanic whose engine rebuild experience consists of rebuilding a few VW air-cooled engines 20 years ago be insane to attempt a top-to-bottom rebuild of the mighty 392 hemi in my '57 Imperial?


From Dan:

It's not impossible. I did my 331 Hemi completely. Before that did a lot of rebuilding. I have some very good sources and would be glad to help.

From Rodger:

Anybody can rebuild your car. All they need to do is to read the notes and clean their mess as they go. And take notes or pictures as the take it off .

From Kerry:

Other than size, weight, and # of cylinders, about the only difference is the lack of water pump. Still a four stroke. You can do it if you take your time, read some books, and ask some advice.

From Arran:

The Chrysler hemis are really no different then any other pushrod V8s other then in the valve trains. I spent a good amount of time last summer pounding the pistons out of my 331 as the former owner had let it sit for five or more years with the air cleaner removed and had let it seize. Although most of the parts look to be in good shape, other then a broken skirt on one piston, I think that I will need to rebore it as it has gained quite a ridge. From what I can tell Performance Automotive Warehouse has better prices then most on old hemi parts. They are on the web so send off for a catalogue so you will have something to compare to as you shop around.

From Allan:

You should have no problem rebuilding the engine yourself and the satisfaction you get when you turn the key and it actually runs will be second to none. Just remember the four P's and you will be okay. (patience, perseverance, precision, and prayer)

From Rich:

I think that you should have no trouble doing your Imperials 392 rebuild yourself. I also started doing rebuilds on VW pancake 4cyls & the general rules of assembly are the same. Make sure you have a good shop manual, & the proper tools. A good quality torque wrench would be important. Other than that, it is still the same type of attention to detail. (during disassembly I make things as easy as possible, by getting a box of zip lock bags & a black magic marker.) Then for each assembly, for example, the valve cover bolts, put them all in a bag & mark the bag. This makes reassembly much easier than sorting through a can of every fastener from the project. For things like water pumps & intake manifolds, I take a piece of heavy cardboard, & stick each bolt through the cardboard in the same general orientation as it is removed from. This helps because on water pumps, & intake manifolds, you can have several different size & length bolts. Arranging them in cardboard helps keep it straight. Also, push rods should be kept in the same order location , so the cardboard works for them also. Other than that, it is just clean it measure components, & carefully reassemble. Use a good assembly lube to aid in break in. I have done many different types of engines over the years, & the basics apply to all of them. You may actually get a better job doing it yourself, as you may take the time to make sure that all of the details are done just right. To get that from a garage will be very expensive.

Question from Dan (318):

After listening to what others have said, I am trying to decide wether or not I should do a rebuild of my Imperial's 318.

I have never attempted such a big job. It's not the tearing down and reassembling that I am hesitant about, it's the 'getting the engine out and back into' the car that I am leery of. (A friend of mine bought a book and did a rebuild of his 'Cuda's 318 and it worked out OK.)

Positives would be:

It would be a great learning experience. (My son wants to be an auto mechanic and he would be helping.)
I can replace stuff I know might need it anyway. (freeze plugs, timing chain, cam, lifters and maybe even rings.)
I can repaint the engine. (Needs it badly.)
I can redo the engine compartment.
I can leave the car and engine in the garage while I work on it.
It's a once-in-a-lifetime thing.

Negatives would be:

I have no experience at such a large job.
If I screw up I have a VERY large boat anchor.
I'm sure I don't have all the tools I will need.
I don't have an engine stand or a hoist.

If I just replace the oil pump, and clean the screen and there's still no pressure, I'd have to do the bearings anyway right? What would that entail? Send it out to a machine house?

How expensive would it be to have the engine rebuilt by a shop? And, how far into it would I have to have them go? Overbore and all that?? (I hope not.)

Anyway, ANY advice/stories at all would be a BIG help.


From Rodger:

Many moons ago when I was in H.S. my dad got a '50 Pont from a place called San Diego Sports & Imports. He said that since it was not a Chrysler product it needed to be repaired more often any ole way. My nonmechanic dad and I did a "poor man's over-haul" that summer ( Poway, Calif ). The car lasted through me, to my brother Dennis and half way through Phillip. And me, I still talk about how my parents bought a car in order to keep me off the shores of La Jolla.

Go fix the car with your son...

From Travis:

I agree, my 7 year old son works on my cars and trucks with me.The best time you spend in a day is with your kids sharing your passions and interests.

From Jeff:

If you want to keep the car original, the first thing to do is buy the book, "How To Rebuild Your Small-Block Mopar" by Don Taylor. I think it is available at Amazon. I can't say enough good things about this book. It takes you from opening your hood to firing the new motor up and driving away. It is a very simple format that is written for the inexperienced. Just be realistic about the cost, with the machine shop work and high quality parts like rings, bearings, gaskets etc (don't bother buying cheap crap with all the work you are putting into it) and hardened valve seats for the unleaded gas, it adds up. There is some things you just can't do like the bore and hone, deck the block, balance and valves. If your 318 is a high mile motor, it will have to be bored about 20 over to make the cylinders round which means new pistons. All other parts like rods, cam, lifter, pushrods, crankshaft will have to be inspected and magnafluxed by the shop to see if they can be used again. You should buy a quality "clicker" torque wrench to keep. You can rent piston installers, ring gapper, engine hoist. I suggest you buy an engine stand (about $79 at Price Club) because this project will take 5 times longer then you think. I'm not trying to discourage you but if you can do this for $1500 you are doing good, remembering your labor is worth $0. The other alternative is to buy a Mopar 360 crate engine with the install kit for $3500 and drop it in, or a real okie job of cheap parts and quick work with lots of shortcuts that you will have to do again in 6 months. I think if you and your son do it the right, the value of the experience and what you will learn can not be counted in dollars. Good luck.

Follow-up from Arran:

I hate to say this but you are performing the same dis-service that A lot of "Car Buddies" do to a new guy, talking a fellow into undertaking a project that's way over his head and his pocketbook.. I think that the first thing that I would do before pulling anything is to do a compression test on each cylinder then he will know whether he even has to mess with the top end. If it turns out that it needs a major overhaul I would search around for a Caravelle or Fifth avenue for a donor engine, 318's are a dime a dozen and not worth dumping major money into.

If he wants to rebuild the original engine there are some ways to keep the costs down but it basically comes down to one question; stock or rod? If he wants it stock he won't have to go through many of the procedures or buy the same sorts of parts that you would if you were building it up. For example the difference between the price of a set of cast pistons verses forged ones can be as much as 50%. In a street engine you do not have to worry as much about perfect ballance between con-rods as you would a race motor, and so on. Magna fluxing might be worth doing on a used replacement part in unknown condition but I think that it might be overkill to go to this expense on a working engine that is never going to be used for racing. I would say that he could buy a decent rebuild kit for under $500 dollars through any auto parts store, or reputable mail order outfit, and end up very satified with the results.

From Rob:

The other alternative is to buy a Mopar 360 crate engine with the install kit for $3500 and drop it in,

It's not that easy. I'm going this route on mine. It already had a 360. Problem one the accessories don't line up with the brackets. The thermostat housing is in the center which means you probably lose your a/c and then you'll have to fab up some brackets or use some non-Imperial brackets. Obviously you lose the air pump. It's also taller than stock, which may or may not be a problem. On the bright side, the 300 hp motor is only about $3000. Supposedly they have an offset thermostat manifold which is coming out, but I don't know when.

Question from Bill (413):

Just got the pleasant news today from the mechanic I brought my Imperial to for the engine rebuild, that his cost alone on the rebuild was going to be around $4,000.00, and that I would end up paying around $6,000.00. I told him for six thousand I could go buy another '59 and swap engines, and that I would be there to pick up the car tomorrow. He was telling me he was going to put in brand new pistons, a new crank shaft, new valves with stainless steel seals for non leaded gas, and all kinds of crap, but the truth is when I got the car back how would I know if all of this stuff was in there? Fortunately the car is in an area where there are literally hundreds of mechanics, so I'm sure I will find someone to do it at a reasonable price. If the going price for a new V-8 rebuild is around $2,500.00, why are they trying to soak me on my old '59, which is much easier to work on? I certainly don't look rich when I go there, on the contrary with my casual shorts and old tattered t shirt, I look just slightly better than some bum off the street. I guess I shouldn't be bringing it to shops which specialize in antique automobiles. I will keep you posted on the outcome of my quest to get my '59 back on the streets again. For an engine which is so straight forward and easy to get at that even I have done minor repairs on it, you would think a mechanic would jump at the chance to work on it, and not charge an arm and a leg. The engine on my Nissan is so crammed into the engine compartment that I don't think I have ever seen a spark plug in there. Oh well, life goes on!


From Arran:

You are right to take your car someplace else, that mechanic is full of bunk. Never have I heard of replacing a crankshaft as being a standard part of a rebuild, especially in an engine with a forged steel crank. The only exception to this would be if the crank broke or had been run with a dry bearing so long that it wore down one of the journals to the point where it couldn't be reground.

As for rebuild parts your nearest stop should be the auto parts store. The 413 is an RB engine, other then pistons and rings there are so many parts that it has in common with 383's and 440's that it isn't funny. For new pistons, if needed, talk to Egge machine and order a set of new rings to match.

From Steve:

I agree that $6K is ridiculous for a rebuild. Pistons are the only piece that would be hard to find and those are readily available if you are willing to pay $50 each. I spent around 2K on my engine with me doing the removal and reinstall. I think you will find someone to do it for your original estimate of $3500.

I hate to say the same thing over again but I really think you need more diagnosis before committing to a whole engine rebuild. From your description I believe that you have carb issues that could be cured for a couple hundred instead of a couple thousand. I sure wish we lived closer together so that I could look at it with you.

I know how hard it can be to find a good mechanic willing to work on these beasts. In their defense you could probably fit three normal cars in the space that the Imperial takes up and make twice as much money in the same amount of time replacing throw away parts on new cars... You have to find someone who shares your passion for the old cars. I haven't been lucky enough to find anyone like that myself but I have the added advantage of having a garage and have been working on them for 20 years now.

From Kerry:

Find a new mechanic and distrust anything this guy tells you. He's a bloodsucking sh--!

You can buy ALL the parts and machine work, bore, turn crank, valves, etc for $1500 plus labor all day long. 40 hours of lavor is a gracious plenty. At 40 bucks an hour shop rate (which is higher than most rates) which should cover R&R, you're looking at 3 grand. The guy is trying to rip you off. Get out while you can.

From Tim:

Exactly. $4,000 is dealer pricing. Hell, for that price, you could probably take it to a street rod shop and have them completely rebuild and replace everything, with polished valve covers to boot. You might locate other people in your area driving older cars (especially Mopars) and ask for a reference to someone they trust.

From Hugh:

You are getting soaked, no doubt. There was almost a consensus from your first post that your actual symptoms were caused by poor fuel delivery and possibly coolant issues. May I suggest you start with a tune up. Your engine runs fine at idle and is neither blowing smoke nor burning huge quantities of oil, if I recall correctly. The new brake booster is replacing one that was full of holes and this may be affecting the timing. See if it makes a difference. It always has worked wonders for me. If necessary, get the carburetor rebuilt if the car still isn't right. An engine coolant flush wouldn't hurt, either. Where I live its advisable to get this procedure done every year.

A rebuild is a wonderful thing but it is the solution to what ails you? I have to say no because the engine is OK at idle. I have had to replace a failed booster myself and a tune up made a significant difference to how the engine ran after I got mine to stop leaking. I even had to tune mine by ear as the marks on the harmonic balancer were impossible to find with a timing light. I changed the plugs because it was so cheap to do so. I think the distributor is far easier to reach on the 413 than it is on the 392.

I think your car is starving for fuel at anything above idle so a carburetor rebuild, or replacement, may be in your future. When a car runs lean it runs hot. Run it rich for a while and see what happens.

What reasons have you been given for rebuilding the engine. Is it the valves or what? Was a compression test performed? Are the rings bad, or what? The key thing to getting the right answer is to ask the right question. There is a disconnect between the solution you were given and your immediate problem. My 392 is being rebuilt right now due to excessive oil consumption but it was running pretty OK otherwise. I drove it to the shop and even in stop start traffic it was not running hot or rough.

I don't know how confident you feel about your own abilities to work on the car yourself. No one knows it better or cares more. I pretty much rebuilt the top end of my engine myself and, trust me, if I could do it so can you. Accessing the distributor on the 392 is a major pain requiring an old shaped wrench and more dexterity than I normally possess, but I have learned how to do it and have always achieved a good result. I tune it like I would a radio. Get it to sound bad then get it to sound good, then try it again at with more throttle. Listening, really listening, to your engine is a marvelous experience. Learning how to do these things for yourself is so beneficial. It decreases your dependency on mechanics who really don't want to work on your car. It will hog up one of their bays for days on end while a similar job on a more modern car with more readily available parts will be in and out in hours.

A shop explained to me that this is why the quoted price for working on my '58 was so high. It is their 'Go away with this unprofitable, unfamiliar, difficult to find parts for, time consuming, hunk of junk' price. Specialist shops with real mechanics cost a fortune and there are a lot of people out there that are willing to pay these prices on their collector car. The best solution is to learn how to do as much as possible yourself. It adds an amazing dimension to the hobby. It decreases your financial outlay and increases your satisfaction.

From David:

I second Tim's comment about Mopar clubs. If anyone knows where to get work done on our engines, it's those guys and gals. Heck, they might even invite you over for a beer and do it with you. We have top of the line engines, and the A-, B- and E-body folks practically froth at the mouth when they see what torque and horsepower numbers we take for granted -- stock!

From Kate:

I must agree wholeheartedly with Kerry - we got the 413 in the big truck completely overhauled, heads, the works, including new clutch pack, for $2400 total - and it's NOT cheap out here. If you can't find an automotive "car" shop, try checking with the truck guys - these 413 engines are still VERY common in trucks and busses, and you will find the people more down to earth in some cases.

From George:

I have to agree with so many ohter people who have posted here. If you are not capable of doing the simple tests like compression and a tune up you need to find a mechanic who shares our love of old cars. You may have to do a bit of searching. Not knowing where you live it is hard to tell you where to look. If you are in a big city area perhaps looking a bit further out towards the suburbs / country. I have found some pretty good mechanics outside of town.

Question from Frank (413):

If I wanted to have this engine perform AS NEW, would this mean an engine REBUILD or are there options to explore? The engine sounds great and is very quiet. I would like to have it perform like it did when new, if possible. At present, I have it maintained by my friendly Dodge dealer. I have no mechanical sense at all. I just love cars. Can the dealer be a source for rebuilding the engine?


From Dwight:

Sounds like a leak-down problem to me - probably worn valve guides. The first thing I'd try, if you're interested in just getting rid of the smoke, is a valve job. A lot less money than a rebuild, and while the heads are off, the mechanic can take a quick look at the condition of the cylinders....

From Mikey:

The answer is yes to all, and no as well!  You can go and buy a complete engine ( longblock ) and put your stuff like the water pump, valve covers etc, on it, you can take your engine and go to a machine shop and have everything redone, or you can take the car somewhere and pick it up when
its done.

The point is - when your engine is opened up and inspected, the goal should be to return it to the original dimensions, specifications, tolerances as it was new.  Sure it may be overbored a bit or the crank ground, but the results should be the same between the three.  The condition the engine is in, the individual parts are in, and standard shop practices will determine what your engine needs.

My advice is to talk to your mechanic, or 2 or 3, and the parts places and compare notes on what your getting for the price, the guarantee, and the
time it will take.  

Question from Ken (440):

I have decided to overhaul the engine in my 1978 NYB. The engine only has about 62,000 miles on it but it has an oiling plug. The car sat for many years and was used only infrequently. I think probably instead of just fixing the oiling plug that an overhaul would be appropriate?????. Any opinions on this. Also any information on what cost one could reasonably expect to pay for this?

Reply from Phil:

Before you overhaul the engine, have you ever changed the valve seals? They do go bad with age and crumble, allowing oil to get past the valve guides. Is the compression bad on that one cylinder? Also, have you checked the intake manifold gasket for leaks? This is done by spraying a little carburetor cleaner, wd-40 or whatever, around where the intake joins to the head. Some folks using starter ether for this test too, but be careful, cause it's highly flammable. And if there is a vacuum leak, the idle will change when it hits the area of the vacuum leak, helping you locate the problem area. Oil from the valley area under the manifold, as well as leaking from a seeping valve cover gaskets, has been known to make it's way past a leaking intake manifold gasket. Also, if the car smokes when first started, then clears up, this is another symptom of bad valve seals. I just find it hard to believe that an engine with only 62K on the odometer, would need major repair. You may want to do some more investigation before you pull the motor.

Follow-up question from Ken:

This has been my opinion for awhile now. The mechanic put a spark plug guard on the one plug and after a little rough idle and smoke the car would smooth out and run a lot better. I am not a mechanic or inclined to know much about these things but also felt an overhaul may be overkill for this engine. How involved is the valve seal job and should anything else be done to the engine while this much work is done? I certainly appreciate your note. A guide of hours and anticipated charges for this job would be appreciated if anyone has done this in the past to one of their engines. The car is still a showboat so I feel some investment would be worthwhile.

Reply from Phil:

Well, if it's a showboat, definitely! Actually, the job is fairly simple, but involved. The important thing is having a way to keep the valves in place while you've removed the valve spring to replace the seal. The old fashioned way is to feed a coil of rope into the cylinder with the plug removed, then rotate the engine careful by hand until it stops, that means the rope is pressed against the combustion chamber in the head, holding the valves in place. Be SURE to leave enough excess out of the hole so you can remove the rope later. Most shops use compressed air fed thru a threaded air line fitted into the spark plug hole instead. Either will work. Then with the rocker shaft and rockers removed, give the valve spring assembly a quick sharp rap to bust the varnish holding the locks in place, loose, and compress the valve spring with either a lever type or rotating clamp type valve spring compressor. Once you have the spring loose enough, CAREFULLY remove the valve locks, making sure not to drop either one! Keeping a small magnet handy at this step, it may save quite a bit of cussing, just in case you drop one. Removed spring-retainer assembly, remove old valve seal, usually in fragments by this time or rock hard, clean area , replace seal by slipping new one over valve stem, reassemble. Important note at this point, be absolutely POSITIVE you have both valve locks in the correct position!!!! If you do not have the valve locks correctly reinstalled, the engine will drop the valve, and expensive motor repairs will follow shortly, unless you are extremely lucky, and it only falls part way, even then, you'd have a dead cylinder, repairs were completed again. Also, IF the valve gets away from you and drops into the cylinder, you HAVE to remove the head. Once you have confirmed that valve spring assembly is correctly reinstalled, removed either rope or compressed air from that cylinder, then move onto the next one. Once one side is done, reinstall rockers assembly being absolutely positive that each pushrod is in its correct position on the rocker and lifter, then tighten bolts to correct torque of 25 ft lbs. Reinstall valve cover, go to other side, repeat. That's it! If you don't feel like bothering with this, call around to several garages and get a price on a valve seal job, this is actually a fairly common maintenance procedure on OHV engines, and a big block Mopar is one of the easier ones to do it on. I'd at least try this first before springing the money for an overhaul, especially with only 62K miles on the engine. This should do it the job, or if not, then at least you know for sure it's not valve seals, but with the car running well, odds are pretty good, this is exactly what the problem is. 

This page last updated June 21, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club