Diagnosis and Repair of Your Imperial's Exhaust Manifolds


Imperial Homepage -> Repair ->Exhaust -> Manifolds

Tip from Steve:

Is your Imperial running sluggishly and turning the exhaust manifolds orange with heat?  The 440 in my RV was running sluggishly and turned the exhaust manifolds bright orange while driving.  The cure was to replace the factory Holley 4bbl with a spare Holley 4160-3310 750 cfm with vacuum secondary that I kept as a spare. It was just sitting in my shed so...I replaced the float needles and seats ($20 and 10 min time) and Viola!!...the RV runs and starts just like my Imperial. With a "pump" of the gas pedal, then a flick of the key.  There is a world of difference in the way it runs now.  Even better than before the hot manifold incident.  I am sure glad it was the carburetor and not a plugged exhaust (which is unlikely since it is 5in i.d.)..or a jumped timing chain that I could never see how or have room to replace.  I still can't believe the 440 survived such punishment...and for 30+ miles! As I drove, looking down at the engine as it had orange manifolds and strained hauling 15,000+lbs of RV at hi-way speeds and almost wide-open throttle, I wondered if it was going to make it home.  It did.  So, if your Imperial is running bad, lift the hood and see if your manifolds look like they are going to melt off of your engine.

Tip from Greg:

I want to pass on the name of a great product I have been using to restore my exhaust manifolds. It is called Calyx and is produced in Cincinnati, OH. It is simple to apply (I use a toothbrush) and it is not necessary to remove the manifolds. I have used it on several of my restoration projects and most recently on the manifolds from my '63 Limited Edition Thunderbird Landau. Basically you must get the manifolds clean and as rust free as possible (easier if they are off the engine and can be cleaned in a blasting cabinet but is not necessary). Once this is done, just apply the product (a charcoal colored paste, NOT a paint) to the manifolds. As the instructions say: "A little goes a long way". After Calyx has been worked into the pores of the iron and evenly distributed over the manifolds, just start the engine and let the manifolds heat up. The product 'cooks' into the iron and gives them a beautiful cast iron gray color. It lasts and lasts for years too! I have used so little of this product, I can refinish many more manifolds (hmmm, good reason to go car hunting for others on my 'want list' LOL!) with what is left. A little does indeed go a long way! The cost: a 'whopping $13.95 (plus shipping). Not only do the manifolds look incredible but no more rust too as it removes the rust as you apply it. This is a great product and I thought everyone on the List should know about it. The website for the company is www.calyxmanifold.com. Check it out!

Question from Fred (1950):

We waited a year for our 1950 Imperial due to the exhaust manifold. The man we bought it from fixed it and now just a month later it has broke again. It is drivable, but we want to fix it or replace it. Any ideas?


From Paul:

Those are very hard to find. There are places that can fix yours correctly. Repairing a cast part is never the best option, but if it is the only option, it can be done satisfactorily.

From Sherwood:

The straight eight manifolds are dificult to repair as they lengthen as they get hot. Why can't you use the earlier manifold from 1946 - 50 as I believe they are the same (parts book says they are the same). Those manifolds are not that hard to find.

From Jim:

Do a Google search for " lock-n-stitch " for cast iron repair. They have a process far superior to welding & may have a machine shop in your area qualified to repair your manifold.

From Roy:

It's hard to believe that among Murray, Bob or Lowell something workable couldn't be found.

Also, since the manifold broke, was repaired and broke again, make sure that you identify the cause! There must be some sort of stress involved. Is the exhaust system too rigid or are the motor mounts worn or loose, etc.

Question from Dennis (1953):

I am replacing the entire exhaust system on my '53 Custom Imperial. The guy in Florida I bought the pipes from said there is no gasket between the engine pipe and manifold flange. When I took it apart, I found there is a thin gasket in that area. It almost seems to be metal. Is this a necessary part and now where can I get it?

Reply from Rolland:

The gasket they used back then was a thin metal (perhaps .030) with an embossed ring about .060 wide about 1/4 larger in diameter than the hole. The embossed ring compresses and seals the exhaust flange when it is tightened. It was recommended to use a new gasket each time the flange was removed because the embosses ring was already compressed. I am not sure what luck you would have reusing the gasket or installing it without a gasket. It would depend upon how flat the flange and exhaust manifold were I expect. My experience is that small exhaust leaks will seal themselves with carbon with time. Large leaks however just get worse.

Sorry I can't help with the gasket but I wouldn't be surprised if many of the parts stores don't still carry them.

Question from David (413):

My '65 convertible has developed an exhaust leak. I thought I would be able to get by cheaply and replace the gasket between the manifold and the exhaust pipe. No such luck, it helped but I find that I am in need of a left side exhaust manifold for the 413. It appears to have a few small holes in the top side close to the bolt area, but the leak is in the cast iron not around the flanges. If any one has a set of exhaust manifolds they would be willing to part with reasonably please let me know. The reason for the set is that the heat riser is also leaking on the right one. I might as well change both and get it over with.


From Jim:

For a cleaner looking & more reliable cast iron repair check out Lock-N-Stitch at www.locknstitch. They repair cast iron world wide. I have seen results of their repairs and a video of their method repairing cracks in the valve seat area of the block.

From Marc:

Cast iron can be welded w/ a high nickel rod , but must be properly preheated. You must also note the thickness of the area to be welded.

From Les:

They can be welded, I had my 68 done as one had begun to crack. That was 3years ago. They weld with a powder, its not arc from what I was told by the guy they heap this powder on the crack or holes and apply heat and it turns liquid and runs. I had it done after removing the header at a weld shop.

From Charlie:

It may not be acceptable for keeping a car "pure", but for a practical repair, it is easy to braze. The brass really shows up against the cast iron.

I have done extensive brazing on cast iron manifolds with good results. It can be done with a wire brush (to clean surface) an acetylene torch, brazing rod and flux. It is really quite easy and doesn't require any particular skill. I have done it to fabricate cheepo headers.

I don't know how it will hold up in a really hot manifold but I never had a failure on MOPAR, GM and Renault in-line engines.

I also split the manifold and brazed in a flange to make dual exhausts for my '38 Imperial straight eight. As a High School Kid, I didn't care about originality, but it sure sounded good with 2 1/2" pipes and glass-packs.

From Dick:

I have also done some brazing on cast iron, in my case on bell housings. I found it necessary to preheat the casting to 500 degrees in the oven, to prevent spreading the crack further as I began to braze. I also drilled a round hole just beyond the end of the crack to stop the travel of the crack. I did this in 1967 on a car that I am still driving - it's still holding fine, almost 150,000 miles later.

From Bob:

There is a national company "Jet-Hot" that repairs and does special high temp coatings on exhaust manifolds, in a variety of "colors", including "cast iron". I had my Alfa manifolds done about 5 years ago and they still are very nice. But V-8 manifolds are expensive to ship and the coating costs could be "high".

Question from David (413):

I am getting ready to replace the cracked exhaust manifolds on my '65 convertible. My mechanic says that we have to have gaskets or the manifolds will leak and I will have problems down the road. The field service service manual does not show the use of any gaskets. I guess what I need to know is which one to follow, the manual or the mechanic?


From Brian:

As long as the manifold being put on is not warped. Do not use a gasket. The factory did not use exhaust gaskets and had no problem with leaks. Every time I have used exhaust gaskets on my mopars they leak. I take them off and they no longer leak.

From Mark:

I have heard this before, but I wonder. I know they didn't use gaskets when new, but 30 years later the manifold is not going to be in pristine factory condition. It's bound to have warped some (?). It seems logical that you would need a gasket eventually . . .

On the other hand, your personal experience is a good argument against it.

Quesiton from Chris (413):

I was working on my other classic car, replacing the valve cover gasket, and as I was gently tightening down the bolts, one of them snapped off. I was quoted at least $65 to drill it out and re-tap it. My question for the list is: can I do this myself? My thinking is this: for that much money, I could buy a nice tap set and be ready for the next time this happens on the same car or on my '66 Imperial Crown Coupe.

Reply from Roger:

Just an idea on the bolt. If your bolt was not to long for the valve cover (bottomed out). Sometimes you can just remove the valve cover then use a flat chisel to start the process of backing it out. Use the chisel to start turning the bolt out by tapping it lightly on the right side with a small hammer. This will back the bolt out or start it loosen. Sometimes you can just turn it out with your fingers after it is started. If the bolt is broken off even in the head. Look at the top where it broke, it will be uneven. You can use a small flat screw driver to back it out most times. I own several frod products and have seen this more than once. 6 poopers seem to be more prevalent. I have never had this problem on a Imperial though.

Question from Ken (413):

I finally gotten to the point where I can no longer stand the rusty exhaust manifolds on the ol' '63. I'm gonna grind 'em down and repaint 'em. Can anyone recommend a good, hi-temp, anti-rust paint?


From Joe:

Have your manifolds sandblasted and buy a coating from the Eastwood Co. made to give exhaust manifolds the look of new surface. It comes in like a 6oz can, is organic and has a shelf life period before it rots. You must either take the manifolds off and coat them or try to coat them on the car. In either case they need to be baked within 24hrs of applying the silver coating. You don't want to do this in your oven....really stinks. I did my hi-po factory Mopar headers about 6 years ago and they look very good this far down the road. Eastwood Products: 1-800/345-1178, they are out of PA....they'll send you a catalog.

From Terry:


From Zub:

On the radio about a week ago they said that the paint company that makes valve cover paint is coming out with a new high heat oil resistant paint in many colors. I can't remember the name. But it was a paint that is in most supply shops and should be on the shelf by now.

From Rolland:

Seymour makes a paint for manifolds called "cast blast" for exhaust manifolds. They claim it withstands 1200 F, which may not be high enough for cherry red manifolds. I have purchased a can but have not tried it yet. It gives the manifold a sandblasted look.

From Ron:

Eastwood sells 2 manifold coatings.............one is a silver/gray and the other is a charcoal gray. Both work very well and are $18.00/ pt. The pt. is enough for 2 sets of manifolds. I don't recommend the sanding and grinding. Any local auto machine shop can sand/media blast them for approx. $20.00 while you wait. After that, just wash them with TSP and water, dry and coat with your choice of material. The coating cures when you first run the engine.

From Ed:

Another option is to send them to JET HOT. They do a metal finish directly to the manifold. Their product came out of the aerospace community. I believe different colors are available. We use it in our shop for some of the competition exhausts we build. It is really a metal powder coat. Lasts for ever, keeps manifolds cooler! Very big in racing. You can find them in the back of most race/car mags, like HOT ROD.

From Bob:

Ditto on the Jet-Hot. It will be much more expensive than Eastwood's and you must send the manifolds away, but they did a great and efficient job on my Alfa manifolds and they look very nice three years later.

Question from Paul (413):

Has anyone put headers on an Imperial - I'm also looking for the right side exhaust but I'm considering headers for my '65.  Would 440 exhaust work on a 413?


From Stevan:

Hooker makes and sells a set of Chrysler C-body headers the price is about $400.00 to $475.00 a set.

From Carl:

From what I gather the B body headers from similar years will fit, but make sure to get them ceramic coated to look good for years to come. If you have a local vendor of B body headers, measure them and see. I am afraid of the PITA it would be to swap starters and sparkplugs etc if I slapped headers on my 300.

From Rodger:

The Right Manifold on the 440 is about 1 1/2" longer on the down-ward portion than the 413 part (right for right). Other than that, they are the same. If you look around for a manifold from a 440 Six Pak/TNT/Magnum engine, it will go on either a 413 or 440 eng (your local muffler shop will need to assist you for the pipes will need attn*).

The left manifold from a 413 dumps in the middle. If you have a '61-62-63 Imperial you will only be able to use this manifold. I have no knowledge of '64-65 space. The 440 manifold dumps to the rear on the left side. If you find the 440 Six Pak/TNT etc manifold for the left side your local muffler shop will need to assist you (*).

If you go this route no one will ever know that you now have more HP to pull your lead sled and that your mpg figure is better than the average Imperial.

* use 2 1/4" true pipe size from the manifold to the muffler... use muffler's that have a 2 1/4" inlet and outlet ('67 - '71 Hemi/440 Six Pak/TNT/etc) use resonator's (not glass pack's) that are the 2 1/4" inlet-outlet

From Steve:

Haven't seen it mentioned in a while but the mid 60's Imperial isn't a C-body, its a Y-Body, so the headers might not necessarily work. Don't know about early 70s, on the other hand you might be able to get a C-body exhaust manifold to fit. I've found significant variations between year groups on exhaust manifolds. For instance the 74 Fury 400 manifolds I salvaged for my 64 don't fit: Pass side out-pipe mount bolts clocked wrong, drivers side is mid-rear dump on 74, center dump on 64 (steering box locations different. I'm using 440 heads on my 413 now, they bolt right on, so you shouldn't have any problems there.

Question from David (440):

Would anyone care to share their advice on how to change an exhaust manifold gasket on a 440 for a '73 Imperial? The offending gasket is on the drivers side. 


From Kenyon:

440 exhaust manifold gasket replacement:

Be thorough and patient.

From Bill:

Although I have not seen your particular application, I assume by your question that your manifolds won't slide off the studs enough to pull the gasket off, or put a new one on. We had a tight fit on a friend's 440 'Cuda. To change the gaskets, we slotted the lower half of the gasket's bolt holes, and slipped them straight down over the studs. To remove the old ones, we clipped slots in the bolt holes with a pair of thin wire cutters. They did not leak.

From Steve:

The PS pump and brackets need to come off. Pull the exhaust pipe loose at the bottom and take the bolts out of the manifold. Wiggle the manifold around, cuss (a lot), scrape all the skin off your knuckles. Once an appropriate amount of blood has leaked from your hands the manifold will come right out.

If your manifold has never been removed before there are metal keepers around the bolts. You have to bend the edges back to get the the head of the bolt. These bolts just love to break! I can't remember for sure if the bolts go in to the water jacket or not, if they do your block will drain when you pull them out. Also there is no gasket from the factory so don't be surprised when you can't find it.

You can find someone to plane the exhaust manifold smooth again and reinstall without gasket or just clean it up and slap a gasket in there. I much prefer the clean it up method.

From Chris:

Just a couple of tips right off the top of my head, having done this to my ' 72 LeBaron :

1. Remove the battery

2. Drain the coolant, the studs your manifolds are attached to the head with extend into the water jacket, chances are at least one of them will come out with it's nut, allowing coolant to run out, everywhere, drain it beforehand just to save yourself a mess.

3. Remove the rubber inner splash shield from the inner fender.

4. Remove the right front wheel / tire and access the manifold nuts through the opening provided by the previously removed rubber splash shield.

5. The above steps will help you remove some of the bolts that otherwise seem unremovable

6. If you're double jointed that will help too...

From Mikey:

FWIW, the exhaust manifold fasteners on these cars were usually held on by studs and nuts, and yes the studs went into the water passages in the exhaust manifolds. On MOST of these, with the exception being some of the performance manifolds that had a very unique deep nut from the factory, you can replace the stock nut with a BRASS nut , which will eliminate the problem of frozen fasteners and busted studs in the future. The same rule applies to the fasteners between the manifold and exhaust pipes, it may not be a big deal but someone in the future will thank you for making that change....maybe even you!

From Mark:

I'm sure someone else has already touched on this, but in my opinion the key to changing this gasket is getting the exhaust manifold planed before you put it back on. Usually they warp a bit from constant heating and cooling, and if you want a tight seal you need to get it planed. Or you could take a straight edge, like a good steel ruler, and check to see how straight it is, but generally I think they require planing, which is something I don't think you can do yourself. (Well, I can't)

From Pete:

FWIW the B and RB engines did not come factory-equipped with exhaust manifold gaskets. The head and manifold were machined to provide a leak free fit. With exhaust gas pressure below 5 psi a gasket just wasn't necessary.

My 70 LeBaron had an irritating leak that seemed to be right in front of me. I lived with it for years but eventually decided that it had to be fixed. What a job! It turned out that the rearmost stud had broken off flush with the head but the broken piece and nut were still in place.

I can usually get ANY broken bolt/screw out but this one defeated me. Despite hours of effort and all manner of tools I just couldn't get the broken piece to budge. The steering column location didn't help.

I eventually had to pull the head and take it to a machine shop. I pulled the other head too and was glad I did since both were slightly warped. With resurfaced heads, new gaskets, and no leaks my car ran better than ever.

Are you having trouble accessing the nuts? They are a bugger to get at. If they're stuck I recommend PB Blaster as a loosener.

Question from Mark (440):

My '74 Imperial needs an exhaust manifold gasket replaced. Other than a little extra noise, what is the down side to not fixing it?  I am getting horror stories about the problems I may be facing if I go ahead with the repair.  Currently all I am experiencing is a little extra rumble which is less than my neighbor's new truck.


From Kevin:

I had to replace the gaskets on my '69 Gala**e. It is possible that you could warp the heads; it never happened to me, but it happened to a friend of mine.  I suppose you could also warp the manifold.

From Elijah:

I have never worked on a '74 Imperial, so my advice may be in error, but the '71 Imperial does *not* have an exhaust manifold gasket.

Seriously. :o)

Do you have a '74 service manual? If so, check the exhaust section to see if your car actually has a gasket. If not, let me know, and I'll look in the '74 manual I have.

You might simply check to make sure that the manifold is tightly bolted to the block -- it could simply be a little loose.

Also check the tightness of the connection between the manifold and the exhaust pipe. There *is* a gasket at that connection, but it could simply be loose as well.

From Trevor:

I just did this on my 68 Imperial Convertible. My understanding is you can warp the manifold. Check for loose nuts first. Then check the bolts and gasket at the connection between the exhaust pipe and the manifold. Replacing the manifold gaskets is fairly simple (8 bucks for the actual gaskets at Kragen) and a couple of hours of labor. It took me about 3 hours, but then again I'm not very bright. When I replaced mine, it turned out that my manifold surfaces were in fact warped as well. To have the mechanic machine them down and get me on the road was less than 200. Be careful with the bolts that the manifold(s) slips onto. If one breaks, you will be hurting in the worst way. Now it sounds absolutely awesome (the little I actually hear) and was well worth the effort. Have fun.

From Steve:

Is your leak at the head or at the crossover pipe?

A common cause for exhaust leaks at the manifold is when a car is run thru a huge puddle that is deep enough to douse the hot manifold with large amounts of cool water. This is known as shock cooling. The manifold will warp and possibly crack. That is why it is important to have the splash-guards in place in the inner-fender wells....and to avoid large puddles.

I doubt there is a gasket in there. If you want to install one (I would), I'd suggest the use of the steel-shim type. Be sure to check the manifold for cracks and warpage first. If the manifold is warped, it's mating surface with the head can be planed-down by a machine shop.

Removing a manifold from a '74 is not for the faint-of-heart.....but it can be done. There is more underhood clearance on the '74-5 Imps and '76-8 NYB's than earlier years. Kerry P just changed one on a '73. More power to him for that!

Unhooking the crossover pipe from the bottom of the manifold isn't too bad of a job. It is attached simply by 2 nuts and bolts. If they snap when you try to loosen 'em...it is no big deal because you should use new hardware anyway. I always try to snap 'em so I don't have to unthread 'em. The crossover pipe is not attached like GM's which have a few wimpy studs threading into the manifold.( I remember getting in there with a torch to heat the nuts up so as not to snap the studs...but no matter WHAT, they'd ALWAYS snap off flush with the manifold. GRRR! JUNK! <--that is one of the reasons why I quit being an auto mechanic and became a lazy pilot...hehehe.) Thank You MoPar for the making the task of taking off the x-over pipe easy!

Where the manifold bolts to the head is another matter. You DON'T want to snap those! If one snaps off flush with the head...Uh-oh! Quality tools will lessen the chance of rounding-off a bolt-head. It also helps to *Whack* the bolt head once or twice to "set" the bolt in the threads....then loosen. Be prepared for an Anti-Freeze bath...because the bolts thread into the H2O jackets. Left-to-loosen...right-to-tighten.

Question from Chris (440):

On a 72 440 I would like opinions on whether or not to install a gasket between the manifold and cylinder head, I've seen it done both ways with varying results. The factory didn't use them, is there any reason to install one now? Should any sort of sealant be applied with the gasket? Without ?


From Rodger:

They go on dry.

From Jim:

Since I'm about to remove an exhaust manifold to get at the heat riser valve, I've been pondering whether I want to reassemble it with a gasket where it bolts to the head (won't look original) or try it without. My only hesitation about doing it without is based on an experience I once had working on another brand of car that also used no exhaust manifold gaskets. I tried to do it without gaskets and it wouldn't seal. It seems that the two surfaces are ground very smooth and the end result is a seal something like what happens when you stick one glass inside another and can't get them apart. Its so smooth there's no way for it to leak. This particular one wouldn't seal and there wasn't a machine shop in town that wanted to plane down the mating surfaces so they would be smooth again and seal. They couldn't get past the fact that I didn't want to use a gasket.

At the time, I was young and so were all our Mopars so I just used gaskets on them as there was no thought of worrying about originality.

Question from Jim (Switching from 413 to 440):

Has anybody had good results bolting a 413 - 440 manifold back to the head without a gasket and without it subsequently leaking?


From Arran:

I have an idea! Try using furnace cement or one of these new high heat silicone products sold for automotive. It couldn't hurt.

From Brooks:

I have successfully used only copper silicone (in the tube) on an Oldsmobile 455. No gaskets -- just the silicone. Works great. Did it years ago, and it's been hot-hot-hot and doesn't fail. If you look on the package, it specifically lists exhaust manifolds as an application.

You could put it on, bolt it up, let it set, and trim off the excess with a razor blade, and it just might not be visible anymore.......

Question from Chris (440 interchange):

Will the exhaust manifolds from a '72 New Yorker correctly fit my '72 LeBaron?


From Elijah:

I'll have to check the parts book to be 100% sure, but I would be VERY surprised if the manifolds would not interchange. I think they should be identical.

From Peter:

Don't have my Hollander handy but I'm 99% sure that the manifolds will interchange. You can check casting numbers to be sure.

From Mark:

I have '72 RH manifold on my '74 Imperial and they fit fine...

Question from Tim (440):

I had my Car at the mechanic to replace what I thought was going to be a exhaust manifold gasket. However, I now need a drivers side exhaust manifold for a 1966 LeBaron. If anyone knows some places to try please let me know.

Reply from Tim:

If your exhaust manifold is not cracked, have it machined flat again. I almost replaced one not knowing I could do that. If you need to replace it try Lowell Howe.

Question from Allen (440):

I had my Y-pipe put on today, and noticed quite a bit of improvement, but hearing some residual noise, opened the hood tonight in the dark and could see some sparks when my friend gunned the engine - down low under the manifold - so there must be a deficient gasket in there....oh well, back to the garage yet again. I also hear at idle or when accelerating mildly a 'pfft -pfft' sound - did I describe it well - my friend [who is 50] says that's your points, Al - get new ones and a condenser while you're at it. Sound right? The car starts great, but the mileage - about 200 miles per tankful and the pffft pfft and slightly less power than I think I should have tells me he might be on to something

Reply from Pete:

Pfft Pfft. Oh boy. Get ready to pull the exhaust manifolds. Points and condenser don't make noise.

Question from Bill:

I have a broken stud inside the head that was done by the PO. Being tired of the exhaust leaks, yesterday I decided to put new exhaust on. I was very surprised to find that there wasn't even any gaskets between the manifolds and the heads. Well, to make a long story short the broken stud is the first one on the drivers side. Thought I could drill it and use a screw extractor. Drilled it and of course it is the water jacket so all the antifreeze came pouring out. Picked up a screw extractor at the local hardware store, wanted an easy out but none to be found in this little town. I could not get the bolt to budge at all with the extractor. Eventually rounded off the end of it. Thought about drilling the bolt more but afraid to screw up the threads. Then thought if I did, I could use a heli-coil but not sure if this would be smart in the water jacket because of possible leakage. Anyway does anyone have a trick or another idea on how or what I may try to get that damn bolt out without damage? 

Reply from Luke:

I've just been through all this only 2 weeks ago. Started with one stripped stud then all the other got the same idea and gave way on me. I'd try drilling it out to the next size thread extractor they come in a variety of sizes. Go to the largest you can and still safely not touch the head in any way. I know it's bloody awkward getting in there and you dread pulling the head off altogether. Squirt plenty of CRC or similar in there (you've probably done this. It's a great feeling when they finally come free though. Hold that thought. Have you used the thread extractor with the counter thread spiral? These screw in and lock the other way as you turn the thing anti clockwise.

Question from Zeke (440):

I have just bought my exhaust manifold gaskets and am replacing them after this weekend.  However, I just received my 67 FSM and have a part
on the exhaust that is broken and I don't really know what it is and does. It is called an exhaust temperature valve (I think) and it is very
broken on my car. It sits on the end of the passenger side exhaust manifold where the manifold meets the exhaust pipe. The thermostat on my
exhaust temperature valve is broken and the valve just moves freely. My questions are:

1. What the heck is this thing?
2. Do I need to worry about replacing it (its a PITA)
3. I think I know the answer to this question, but I will ask regardless, can I find a replacement?


From Jim:

This thing allegedly helps the engine 'warm up' more quickly. Mine doesn't work, either. in fact, were the right manifold to come off, I'd likely remove this device. I don't think it would hurt anything to not have it installed. It forces exhaust gas back into the crossover passages in the intake to warm the intake. Some cars (hi-perf, mostly) don't have crossovers in the intake or have them blocked off to keep the intake cooler. Ultimately this results in lower air temps (denser) and more power. Good luck getting parts. If you can't find new parts, at least make certain the valve is open upon installation so the exhaust gases from the mighty V8 can find their way out.

From Dick:

The valve you are describing is the "heat riser valve" and it's purpose is to improve drivability (meaning throttle response) during warm-up in cold weather. Depending on where you live, this is somewhere between "nice to have" and "absolutely useless". If you live in the Yukon territory, perhaps it is worth your while to try to find a replacement. If you live south of the 40th parallel, it isn't worth bothering with, just have your muffler shop braze it in the open position and forget it. Anywhere in between, it's your call, but it is not really essential, and it opens as soon as the exhaust warms up anyway (maybe 2 minutes after you start the engine), so it is not a big deal.

Question from Mark:

A few months ago I had the R exhaust manifold on my '71 Imperial replaced with an exhaust manifold that I know was from another '71Imperial.  I'm a little unhappy with how loud the car is. I'm trying to figure out why it would be so much louder - obviously on that side - and I'm trying to figure out what to check first. Any ideas, anyone?


From Bill:

Can you determine if the noise is actually coming from the manifold's connection to the motor or from the pipe? It is very possible that the replacement manifold was warped some and unless a thicker gasket was used, you may not be getting a tight fit. Retighten the exhaust manifold to the specs in your FSM with a torque wrench but do it when the motor is hot. Use work glove so you don't burn your hands. Have you taken it back to the mechanic or shop that did the work?

From Loren:

Locate the source of the noise with a length of rubber tubing, like heater hose or fuel line. Listen to one end and position the other at various points around the manifold where it meets the block and "Y" pipe. You'll be able to tell exactly where the noise is coming from without trying to get too close to those hot parts. TIP: Keep track of the end you place against the engine so you don't wind up with grease in your ear the next time you use the hose to locate a noise.

From Andy:

Check and see if the exhaust doughnut is sealing properly it might just need adjusted also check the nuts on the manifold to be tight.

From Kerry:

I had the same problem on my 73. The following test will tell you the problem. NOTE, this works best with a COLD engine. The manifold gets very hot very fast. Have someone start the car. Put your hand down beside the manifold/headpipe connector. If there is a leak, you will feel the hot air. It won't burn you at first. Also check and make sure the riser valve is free. I ended up putting two gaskets in order to get it to seal.

From Rodger:

Also, start the vehicle outside. Stand back and you will be able to see the leak(s) for you will have puffs of exhaust from other places than the end of the tail pipe.

Question from Roger (440):

I am having some problems with an exhaust leak.  My mechanic says leak is at the engine and could be a problem getting bolts loss and if one breaks in head it could cost 200 or 300 bucks.  Any ideas on how I can prevent that?


From Bill:

Sounds like they are telling you that you need exhaust manifold gaskets. Not that difficult but the bolts holding them on may be a bear cat. It is hard to get a penetrating oil onto the threads of the bolt because of the awkward position they are in. The only way to find out is try. Soak the area as best you can with a penetrating oil or spray. Get a 1/2 inch drive breaker bar and carefully try to loosen them. If you are really wanted to get ambitious, you could pull the heads off with the manifolds and then do a valve job at the same time. Would make the job of removing the manifolds easier. You could grind off the heads of the bolts, remove the manifolds, soak the bolts with a penetrating lube and then remove them with a vise grips. Just some ideas.

From Dick:

A good independent exhaust shop should be able to heat the bolt with a gas torch enough to release the rust without damaging anything else. Go to a shop that is privately owned, and has been there at least 20 years.

Question from Roger (440):

I have noticed there is a flexible pipe from the exhaust manifold to the air intake on the 74 that's not on the 69.  What is this for?

Reply from Steve:

The flexible hose that runs from the drivers-side exhaust manifold to the air cleaner housing "horn" is used to direct warm air into the air intake flow when the outside temperature is cold. The warm air prevents hesitation in cold weather and prevents carburetor icing. A small vacuum line is attached to that round thing (which I believe is called a Thermac) on the air horn. In cold weather, the Thermac closes off the flow of outside air via a vacuum line and only allows the flow of warmer air from the top of the exhaust manifold. The Thermac acts as a flapper door. If the intake air is too cold...which makes it more dense...it requires a "richer mixture" in order to have the proper fuel/air ratio. Otherwise the car will stumble...etc

Question from Kerry:

Is there a definitive way to tell the difference between a clicking lifter and an exhaust leak from a cracked exhaust manifold?

Been down the road of replacing lifters only to find it was a cracked manifold once before.


From Jim:

If the lifters are hydraulic, the clicking should cease once oil pressure has built up to take the slack out of the valve train. If it's an exhaust manifold leak, the clicking will always be there.

From Allan:

The best tool that I ever found for this and other noises is an electronic stethoscope, usually available from a parts store for around $30.00, in lieu of that, you can remove the valve covers and use the old finger method of touching the rocker arm with your finger to feel for the shock of the lifter hitting or use a thin steel rod or vacuum hose to your ear and the rocker. Makes one heck of a mess though.

From Dick:

use a stethoscope, but a short length (3 feet?) of rubber garden hose works almost as well. If you have a cracked manifold, you can home right in on the crack with the hose by blocking one ear and listening to the other end of the hose. There will be no doubt, because you'll hear the puff of air each time the closest cylinder fires. Also, the manifold crack tends to get less as the engine warms up, it is worst when ice cold.

From Phil:

A mechanic's stethoscope, with a probe , should do the trick. Also, sometimes if you wave your hand, Carefully! around the exhaust manifold at idle, if you got a leak, you can feel the exhaust coming out. The real fun comes in when you have a lifter ticking and an exhaust leak!

From Leo:

A cheap way to check is with a length of broom handle. Hold one end to your ear and the other end on the valve covers in different spots.

From Steve:

Yes, an exhaust leak will increase/be louder when the engine is put under load. A "ticking" lifters' noise will remain constant under load.

Have someone sit in the car with their foot on the brake...and have them step on the gas-pedal a little while you listen underhood.

From Kenyon:

For mine, the exhaust guy had on gloves and ran his hands around the manifolds/pipe mating joints. When he felt airflow, he had found the leak via the pulsing exhaust leaking out. This was while I was in the car holding it at 3k RPM.

Leak on mine was at the pipe/manifold joining flange.

Not a good technique if the crack is on the underside of the manifold next to the block, but that's not the stressed area, for the most part, and I think the metal's thicker there, anyway.

Gloves used were finely knit (cotton, wool?) and may have been specific to welding, but not air-proof rubber or something like that.

From Bob:

Before you do anything else, check around your heat damper.  This is where I found mine one time but I did what you have done and felt like a fool when it was that.  The heat damper had rusted out and this left 2 holes in the exterior where the heat damper was.

This page last updated August 4, 2004.  Send us your feedback, and come join the Imperial Mailing List - Online Car Club