It started with a cracked stock exhaust manifold on my ’64 /6. Had a spare stock manifold set and put it on with a felpro gasket. Result was leaking at the gasket and a new leak at the exhaust pipe flange. Read the archives here and reinstalled with a new Mr. Gasket manifold gasket and a new exhaust pipe flange gasket. Used a torque wrench this time and used some recommended blue high temp gasket sealer on the manifold gasket. Tightened everything carefully in sequence but did not separate the intake from the exhaust manifold. Result 3 days later was that both the exhaust manifold and exhaust pipe manifold gaskets were blown. Went to a junkyard and got a manifold set out of a ’68 Volare, checked the flatness of the manifold set with a straight edge, installed carefully with no sealer and new gaskets. Did not separate the manifolds. When I went to put on the stock Holly 1920 carb noticed that the intake manifold was different with no hole for the PCV. Installed the carb anyway with plugged PVC, this time used Permatex copper sealer at the exhaust pipe flange. Result was no idle and an exhaust leak at the exhaust manifold gasket. Decided to use my stock intake manifold (to get back idle). This time, with yet another new manifold gasket, I installed everything, with a torque wrench, in exact order and of course the manifolds were separated. I had to enlarge the inboard hole in the intake manifold to accommodate a bigger stud from the exhaust manifold (intake to exhaust connection). I used no sealer and did not disturb the non-leaking exhaust pipe flange. Result is major leak between manifolds. I plan to reinstall using sealer between manifolds and possibly two metal gaskets. Any help would be greatly appreciated.

I've had success in sealing exhaust leaks by using the fibre-rope gasket and adhesive(like you would use on a woodstove) in place of the usual gaskets available at the parts store.

It can certainly take the heat, and it's flexible enough to withstand vibration while maintaining a seal.

It IS however, as ugly as sin, so if looks are important...
and I doubt you could use this approach on the cylinder head to manifold connection.

Hope this helps (or gives you a good laugh!)

Boy, you can't say you didn't give it an honest effort! You said you researched previous threads, did you get the part about which washers and nuts to use where? And about the correct tightening sequence?Because it does matter. I have heard a coupla guys recommending the extra thick gasket sold by Cox Bros.
I think I would concentrate on sealing the manifolds to head, first. And deal with the exhaust outlet later. You may have to cut the head pipe on a straight section, insert a coupler, and then reclamp it with exh clamps after you attach the end to the exh manifold flange. When you torque the nuts, try sneaking up on the final torque. I don't remember what the torque spec is off hand, but let's say its 20 ft/lbs. So approach it in increments, say just snug, then 10'#, then 15'#, then finally 20'#.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

At this point the manifolds to head is ok and the exhaust pipe flange is ok. Only problem now is manifold to manifold. I am going to try to use sealer (copper silicone) on that metal gasket, and/or maybe use two gaskets. And hope that when I remove the manifolds from the head that I can get a good seal again (with a new gasket of course). BTW I was EXTRA careful using a torque wrench in tightening everything to specs.

Only other thing I can think of doing is to join the manifolds together off the engine and take them to a machine shop to get them flat. But I really don't want to do that.

I wonder how it was "professionally" done back in the '60's?

I am not an automotive machinist per se, but I think that might be pretty tough for most automotive shops to do. But bolting them together, first, might be pretty revealing as to how flat and parallel the surfaces are.
I read your post several times, and it seems to me, if your head/manifold surface is flat, I'd have the int/exh manifolds 'just snugged together', then I'd 'just snug' the ass'y on the head without a gskt. Use a feeler guage to chk that its flush everwhere, no gaps. Then I'd torque the intake to exhaust bolts. Remove the ass'y and recheck for parallel and straight. If its not straight/parallel within 3 or 4 thousandths, then there's going to be too much stress on things, and something is going to break/give.

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'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

As Bud suggested, doing a trial fit-up and checking for flatness and gaps is what you need to do. I tend to use a little thicker feeler gauge but the same checking process.

Sounds like you have some used / warped manifolds and you will need to do some grinding / surfacing to get everything flat and square again.

It is no fun being in this kind of jam where nothing seems to work. Everyone hates having to redo a hard job. Based on that, here is some text out of my files on a manifold install, just a collection of stuff at this point but you may get some ideas out of it. (I guess I should add some photos into this draft and post it into the articles section)
DD

(Ext. Man. Draft)
We will review the different exhaust manifolds available for the SL6 and discuss manifold preparation / installation
All SL6 exhaust manifolds are basically the same and will interchange with all SL6 engines 1960-86. There were some minor changes made to the exhaust manifolds over the years which added more reinforcement ribs and changed the choke stove pocket design. The first SL6 exhaust manifolds had no external ribbing and as a result, these crack and break easily. From these first manifold castings, this long cast iron exhaust manifold would prove to be a challenge to keep in one piece, as a result, the engineers added reinforcement ribs in an attempt to prevent cracking. Two external ribs were added in 63 to stiffen the body of the manifold. 1970 saw another bottom rib and ribs running up each runner "leg" added, along with a revised (round) heat riser valve counterweight. By 1980 a thick section was added to the heat riser area's rear wall and this "boss" was drilled and tapped for an O2 sensor.

The key thing to remember is that this big-long exhaust manifold is designed to "slide" across the gasket surface and move around as it heats & cools. A stamped steel gasket is the best for allowing movement but is also the hardest to seal. The thick material gaskets are the opposite, easier to seal but they don't allow much manifold movement, which can lead to a cracked manifold. The manifold hardware is an important part of the installation. The special washers allow the manifold some movement while holding it down for sealing. The correct hardware must be used in the proper locations. The two acorn nuts go on the two top, outer end studs, with the coned shaped part of the nut fitting into the dished/conical part of the round brass washers. The center three studs get cup-shaped round cast iron washers, cupped faces towards the head. Everything else gets triangular butterfly washers. Note that "later" SL6 engines came with only one round conical washer in the top center position, all the other were triangular type. This combination is also acceptable but installation of the lower, inner triangle washers can be a challenge, especially the one under the choke stove mounting pocket. A little grinding of the parting line in this location really helps to get socket access to that nut. All the tab surfaces where the washers contact the manifold must be smooth and allow clearance on all sides. You may have to grind the sharp corners off the edges of the tab cutouts to ensure this. I use some anti-seize compound on the resurfaced flats to help the manifold "float" under the washers.

Choke Spring (stove) Mounting:
The choke stove mounting pocket came in three permutations:
A cast-in pocket with a small section of the rear casting wall missing.
A pocket area open to the exhaust port and the use of a stamped steel "cup and gasket" to seal the hole.
A cast-in pocket with the entire rear wall removed, this allows room for the Super Six 2 bbl chock stove.

Gaskets:
The factory used a stamped steel gasket between the manifold set and head, this worked well on the freshly machined surfaces of new engines. For used / worn surfaces, use a composition gasket--I like NAPA's #MS-16030 better than Fel-Pro's gasket for this application. There is also the very thick Mr. Gasket #320 as well as special "engineered material" gaskets from Cox Performance and Clifford. These can be useful if you suspect leakage from from headers because of flange warping. The original type embossed metal shim gaskets don't seal well on used surfaces that are pitted or not completely flat. Forget about the "Fig Newton" gasket, (paper on the intake ports, metal on the exhaust) because these take extra intake / exhaust manifold realignment work to get sealed. This "two-in-one" gasket was sold by McCord and (sometimes) Chrysler's aftermarket parts department.

Gasket Goop:
Sometimes sealer is helpful, other times it is not. If your manifolds and/or the head surface is warped, it can mean the difference between a successful seal or the "rework" of a time-consuming task. The cardinal rule of gasket sealer is best remembered by thinking back to the cardinal rule of grammar-school arts and crafts: "DON'T BE A PASTE WASTER!" In other words, use any sealer sparingly, you do not need a lot to do the job. There is an open debate on where to use what type of sealer. In general, most agree that you can use a good high temp. sealer on the gasket face contacting the head, as well as sealer on both sides of the "heat box" inter-manifold gasket used between the intake and exhaust manifolds. As for using sealer on the gasket surface contacting the manifold ports, I coat that side, Dutra puts a little around the intake ports only and other use no sealer on that side, many racers use no sealer at all. Do what works best for your manifold set-up.

For a long time, high temp. RTV Silicone was the only option for exhaust manifolds. Now, there is something better for this application. It is a blue polymeric gel called "Hylomar". It is much, much easier to work with, more flexible, more removable, and generally much better suited to this application. I have had excellent success with the variety in the squeeze tube labeled "Hylomar HPF/High Performance Formula". Make a thin ring, (you don't need much) around each port on one side of the gasket. It doesn't need to be used so thickly that it gooshes out all over the place but be sure there is an unbroken ring around each port opening. Put the coated gasket on the clean cylinder head surface and press it into place with your fingertips. Now, it's easier to put beads of Hylomar on the manifold side, instead of trying to figure out a way to spread Hylomar on both sides of the gasket before installing it.

Manifold Preparation:
The first step before you disassemble the manifold set is to check the intake to exhaust manifold port alignment. Run a straight edge along the bottom of the port openings or use a new gasket to see if the exhaust manifold is warped. Pay close attention to the end exhaust manifold ports, it is common to see these ports slightly higher then the others in the row. If the end ports are higher by more then .100 it will be difficult to get the end ports to seal. (Very little gasket contact area remains) It is possible to do some minor location adjusting by "offset" grinding / filing on the heat box contact surfaces, between the two manifolds.

After you've disassembled the intake from the exhaust, inspect for cracks and deburr the manifolds. The port openings are the obvious places to grind but also do some work around the cutouts where the triangular spanner washers seat. Another good place to grind is under the choke stove pocket so you have a little more room to fit-in your socket for easy assembly. I also smooth-out any ragged casting parting lines or sharp edges just so I don't nick myself on these while doing the assembly work. Next, clean the heat pocket area of the intake. This is the area on the underside of the intake manifold where it connects to the exhaust manifold. Use a screwdriver to scrape-away all the carbon buildup in the manifold's heat pocket "hot spot" area. Really scrape hard in all directions to chip away as much of the stuff as possible. A spray can of Berryman B12 ChemTool carburetor cleaner helps here. If you wish to be fastidious, have the manifold media blasted. (bead, sand, brake lathe shavings, whatever your local blaster uses) Removing all the carbon from this heat transfer area helps heat transfer to the intake. Note that later intake manifolds have a larger heat spot. Wash-out the cleaned manifold completely after your are done and repaint . This is especially important with intake manifolds that have been media blasted.

Get a can of genuine Chrysler MoPar Manifold Heat Control Valve solvent, available at any Chrysler Corp. dealer, to lube the heat riser valve bushing, this is a must, nothing else works as well. Spray this stuff liberally on inner and outer ends of both heat control valve bushings and work the valve back and forth, flushing / lubing with the heat control valve spray. Do this until the flap operates smoothly and freely. If it is stuck fast, remove the counterweight, (The early flat type counterweight comes off fast) flood the bushings with the solvent spray and whack the ENDS of the shaft with a good hammer. Keep spraying and whacking the shaft back and fourth until it frees-up. A little heat can help free-up a really stuck one.

Next, you'll want to carefully prepare the surfaces for the new metal inter-manifold gasket. The current stamped steel replacement gaskets are poorly designed and tough to persuade to make a good seal so clean and file flat the contact areas. The old, long-obsolete "problem solver" gasket (a thicker metal-asbestos-metal sandwich material gasket) was much better at sealing a worn and pitted surface. My experience has taught me that unless you have reground these surfaces or have a brand new intake and a brand new exhaust manifold, this all-metal gasket simply will not seal on a worn surface. This is the place to use High Temp. RTV Silicone. I use copper high-heat RTV from the parts store or Chrysler Mopar High-Temp RTV to help ensure a seal.

Before we get to the actual application of goop to this gasket, you will need to modify the stamped steel gasket slightly, if you plan to use it with a '70 or older exhaust manifold. Most of these gaskets have a "bridge" part that runs across the center opening, from side to side. This was intended to help direct the flow of exhaust through the hot spot pockets in later manifolds, but this section of the gasket interferes with the top of the '70 and earlier manifold heat control valve "flapper", which sits higher in the exhaust manifold. The later valves are mounted lower in the manifold and don't hit the gasket. To make the modification, use a cutoff wheel in a Dremel tool or sharp shears (fast) or a file or saw (slow) to cutback the straight (non-curved) end of the bridge. Backcutting this bridge by about 1/8" will solve the interference problem, or if you're running a '72 or earlier intake, you can remove the bridge entirely. The valve catches on the corners of the bridge where it meets the side rails of the gasket. All of this will make sense once you see it, but note that the interference won't happen until everything is assembled and torqued, so if you have the early style heat control valve, DO THE MODIFICATION, otherwise your heat control valve may not work right or will get jammed in the closed position on the early style manifolds.

To prep the inter-manifold gasket, brush/blow off all the chips from the bridge modification and then goop a medium-heavy layer of high heat RTV silicone gasket material on both sides of the gasket, all the way around its rectangular perimeter, let the RTV "skin-over" for half an hour or so. To install the manifold set, carefully place the "gooped-and-skinned" inter-manifold gasket right-way-up between the two manifolds, then just snug the three intake-to-exhaust bolts with your fingers, (new, grade 8 bolts, coated with anti-seize, if you ever want to take them out again without breaking them.) then install the pair of manifolds onto the cylinder head, on which you've placed the prepared 12-port gasket.
Install all the washers and nuts. I like to use Dorman's brass nuts on the studs, because they don't seize and they look nice. A brush coat of 'Led Plate' (Briggs and Stratton 93963) or another good metallic anti-seize compound on the stud threads and on the three bolts is a wise move.
As for putting the bottom triangular washers onto the studs, it's easier if you put one washer on the shaft of a phillips head screwdriver or rod, then touch the screwdriver to the stud, then use another driver to slide the washer onto the stud. Another technique is to loop a piece of sewing thread or fishing line through the washer eye, then lower the washer down between manifold runners, guiding the washer onto the stud with a long screwdriver or probe.

Tighten the manifold-to-head nuts; start at the center and work outward to snug, then go back and torque the three intake-to-exhaust bolts to 22 foot pounds. now go back and torque the head fasteners to 10-12 pound-feet of torque, again from the center outward.
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A couple of additional comments on getting the factory intake & exhaust manifolds assembled and sealed-up properly:
Check any used manifold for warpage, use the gasket as your "inspection tool". If the end exhaust ports are more then 1/8" higher then the intake port next to it, best find another manifold.

Always do a "dry run" fit check, assemble the intake manifold to exhaust manifold, with no gasket and the center 3 heat riser bolts "making light contact" but not torqued. Place the assembly directly on the head surface, no gasket and install the fasteners. Look for warpage by using a .010 feeler gauge along the gasket surfaces and mark any places where the gauge slips in. Check the exhaust pipe connection point to be sure the pipe flange meets the manifold surface square and flat, this will give even "crush" on the gasket for a trouble free seal. Inspect around each washer and stud, do some grinding to remove casting flash or make additional clearance if you see any contact.

Remember, this big-long exhaust manifold is designed to "slide" across the gasket and move around as it heats & cools. If you pin it down by over-tightening or because it butts-up on something, the manifold will flex, warp, crack, etc. Be sure the exhaust manifold does not contact a stud or that the washers do not rotate and jam-up in the machined tab notch(s) as you tighten them. Use the correct brass washers on the top/end studs. The only thing that should contact the exhaust manifold are the faces of the washers, not their sides, not the studs, not the intake.(except at the center heat riser pad) Grind away any interference. Do not "force-on" the assembly or it will eventually crack the exhaust manifold, a stud or both.

To align the two manifolds, assemble the manifolds with the 3 heat riser bolts making light contact. (it is a good idea to use "anti-sieze" on all bolts & washer faces) Now install the assy. and all the washers / nuts so they make light contact. Go back and tighten the 3 heat riser area bolts. Check for gaps and resurface or realign parts as needed to remove gaps.

I have a bunch of "special tools" to help with the washer / nut install, the best tool I have is a 1/2" socket with a magnet "insert" that holds the nut right at the the tip of the socket. This keeps the nut from falling out or getting pushed-up into the socket as you try to get it started onto the stud. always tighten the head stud washer nuts from the *center* and work outwards in order to prevent any wrinkles in the gasket. (just like a head gasket, squeeze it out towards the ends)
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"Dutra Duals", Cast Iron Dual Exhaust Set - Installation Instructions
To install the Dutra Cast Iron Dual Exhaust Set is about the same as the replacement of a factory exhaust manifold. It is always a good idea to align the altered rear manifold section with the intake manifold and then have the assembled pair surfaced ground flat, this insures a clean and perfectly matched gasket surface. You can align the pair by first assembling the two manifolds, along with the stainless steel heat riser gasket and the 3 attaching bolts. (It best to use new bolts at this location, the old ones get pretty crystallized and brittle) Tighten these bolts until they make contact but do NOT "crush" the gasket at this point. Install the assembly on to the cylinder head studs (without the intake / exhaust gasket) and assemble all the spanner washers and nuts. Draw these down until they make contact but do NOT torque. Now go back to the 3 through bolts assembling the intake to the rear exhaust manifold section and tighten these bolts to 15 foot-pounds. Use this opportunity to check clearance around all the hardware and the general fit and finish of the assembly. Now the assembly is aligned and you can remove it for resurfacing if needed. (you can now check it with a straight edge)
Before starting the final assembly process, it is a good idea to mark the new intake / exhaust manifold gasket with reference marks to aid in aligning the head ports with the manifold passages. Set the new gasket on the manifolds and lineup the passage opening with the gasket. Once correctly located, reach around and "trace" the manifold's edges onto the gasket with a felt pen. You do not have to get all the way around all the ports, just do a few places you can see while assembling the set-up. Doing this is more important for the front Dutra casting because it is no longer connected to the intake and can "float" on the mounting surface and get out of alignment with the head ports.

Install the new gasket and manifolds using all the factory spanner washers (the 1970 and later "thick ones" are the best) and be sure to use the brass washers and castle nuts on each top end-stud. Watch to make sure the spanner washers DO NOT rotate and butt their edges against the mounting ear cutouts on the manifold. The manifolds need to "float" on the head as they heat and cool so allow clearance EVERYWHERE. If you "pin-down" the manifold(s) because of interference or over tightening, they will flex, crack and break. All the nuts should be torqued to 10 - 15 foot pounds max. Once you have heated and cooled the engine, recheck the tightness of the nuts. Now it's off to the exhaust shop to get the pipe work done. You can run 2 - 2 inch pipes all the way back (a "balance tube" connecting the two at mid car helps mid range power) or run 2 - 2 inch pipes till your under the car then "Y" back into a single bigger pipe and muffler (2 1/4 or 2 1/2 inch) for the remainder of the system. The first system makes a bit more top-end power, the second is quieter. Your choice!
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Would the oxygen sensor used in these applications also be usable for Bob DiBiase's EFI conversion? It'd be nice to have an O2 sensor in a "stock" location for that (and to be able to use it with an air/vuel mixture gauge until then) instead of having to jury rig it.

_________________
'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

I have had good luck following the procedure in DD's post that is right after the part about modifying the metal gasket.

I did the metal gasket modification.

I used a hefty amount of goop and let it skin over. The surface on my exhaust was questionable, but it has been two years and it's still holding.

Wait till you get everything bolted on the engine before you tighten these bolts.

John

Many thanks Doctor Dodge for all the detailed information about this situation. Seems I just gave up too early and should have used sealer on the manifold to manifold gasket (the only leak I have now). What was left out of the procedure is the fact that when using an early intake with a later exhaust (probably a common occurance) the damn inboard hole in the intake (manifold to manifold) has to be drilled out to to 1/2' fit the bigger stud. One question I have left is how long to wait after assembly before starting the engine? Copper RTV high temp instructions say to wait 24 hours for a cure, and I am now paranoid. This car is a daily driver which increases the stress of the job.

Thanks for the hole drill-out info, I will add that in.

You can start the engine for a few moments then shut it off to warm things up for a faster cure. I would say that a few hours heat cycling would do the job. I would drive with a light foot until full cure was complete.
DD

Great directions, all of which I have voliated and I have not had any problems with the manifolds sealing.

The last time I removed the manifolds I decided to split them and do a through cleaning. My manifolds are '78 SuperSix vintage. When I inspected the exhaust manifold, I noticed some hairline cracks. It also appeared that the down pipe section was actually sagging. Extreme heat at some point? From running to lean? Who knows. Anyway, I ground this all down and brazed it up. When splitting the manifolds, the outer bolts that hold the intake and exhaust together snapped. So I drilled them out. You will be interested to know that radiator fan bolts are the right length and size to be used as replacements. A couple of lock washers and nuts and everything is good to go.

I comtemplated gasket matching the exhaust ports. But there is a sag thru out the whole exhaust manifold. The end ports are higher then the center ports. This caused me some concern, but after sizing everything up and profilling the gaskets to the head and then the manifolds. I saw that the port openings in the manifold are actually larger then the ports in the head, and everything really does line up. So I didn't gasket match. I also removed the choke flapper (it was broken anyway) from the manifold and plugged the holes with 3/8" bolts.

You might be interested to know that there really is a difference between the supersix and non-supersix exhaust manifold. The outlet flange on the non-supersix is parallel to the ground and the bolts are parallel to the block. While the outlet flange on the supersix is inclined 5* up and towords the frame rail. The outlet hole is 2" on a supersix and 1 15/16" on a non-supersix. These are the only major differances. Everything else is the same, with the exception of the choke housings, which vary amoungst all the differant years. For instance the choke housing on my manifold has a cutout facing the front of the engine. By the way, those "supersix" manifolds that are being pushed on E-bay are not supersix manifolds.

Upon assembly, I used felpro gaskets and Permatex Orange hi-temp sealer. I liberally coated the manifold/head gasket and the intake/exhaust gasket. I then very loosely assembled the intake and exhaust together. Placed the manifold/head gasket on the head and slipped the manifolds over the studs. I then bolted on the center intake nut and conical washer to hold everthing in place. Then I proceeded to bolt on the the rest, with the appropiate washers. When done, I snugged everthing up, front to back. The rear stud is broken off, so there is no nut at the end. At this point, I walked away for an hour, and rebuilt the carb. When done with that, I came back and tighten the three bolts that holds the manifolds together. I then assembled the carb, linkage, fuel lines and exhaust pipe. When done, I fired up the car and let it run until it warmed up. At this point I shut the engine down and retighten all the bolts.

There were no leaks upon first fireup, and there is still no leaks. The brazing is holding up fine and the rustolem barbeque paint is still on the exhaust manifolds. I guess that I am lucky, but I have always done manifolds this way, and I have never had any problems with them.

You bring up some good points, not the least of which is to spend some time seriously inspecting the 'new' exhaust manifold. Cracks start off small and usually get bigger. Media blasting, and dye penetrant will expose most cracks. Or magna fluxing will work just as well.
Kesteb, I know you're from the Everett area, FYI, there is a very good cast iron welder SW of Lake Stevens. His name, appropriately, is 'Cast Iron Mike'

_________________
'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

My guess is your "luck" comes from using lots of copper high temp sealer on every mating surface.

Dan,
I'm quite sure that all oxygen sensors from that era are electrically the same and will have the same 18mm-1.50 SP Plug Type thread.
Bob D

As a kid, I remember visiting my uncles farms back in minnesota and they brazed all the broken cast iron stuff. If it works on a farm, it should work for me and I don't have to plow the back 40.

When I did the head on the wifes escort, I took it to what used to be Dicks Machine in Marysville. A nice bunch of guys are now setup there. They had some older blocks setting on the floor waiting for pick up. One had a crack that was brazed up. Beautiful job, these guys know their stuff and send out cast cylinder heads all the time to be welded. So if they brazed the block, they must think it is good enough.