Exhaust Manifold Gaskets


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By 312YBlock - 3 Years Ago
Are exhaust manifold gaskets necessary on a 312?
By Ted - 3 Years Ago
That’s a loaded question.  From the factory, exhaust gaskets were not used.  The exhaust manifolds simply relied on a metal to metal fit at the heads.  Once removed, the exhaust manifolds are typically reinstalled with gaskets due to some warpage taking place.  My experience has been that the gaskets tend to promote the manifolds cracking and/or breaking more quickly due to the gasket separating the two and there being a greater heat differential between the head and the exhaust manifold.  Said another way, the exhaust manifolds are distributing some of their heat back into the cylinder head mating surface when no gasket is being used which helps that manifold to run cooler thus slowing down any expansion that causes them to break.
 
More thoughts on this always welcome.
By 312YBlock - 3 Years Ago
Thanks Ted, good information. I’m planning on ordering 2 new manifolds and having them ceramic coated. I think I’ll install them without gaskets.
By 2721955meteor - 3 Years Ago
use the gaskets, but use grade8 capscrews,aswell hardened flat washers(cat hardware would be my  preference as there flat washers are thicker and capscrews have thicker heads. my 1st y was a 1955 272,with no gaskets, constantly tightening the bolts.  just my warped way of doing things
By 55blacktie - 3 Years Ago
Make sure the manifold flanges are not coated. 
By DANIEL TINDER - 3 Years Ago
312YBlock (3/3/2021)
Thanks Ted, good information. I’m planning on ordering 2 new manifolds and having them ceramic coated. I think I’ll install them without gaskets.


If the heads aren’t installed yet, take them & the manifolds to a machine shop first and have the mating surfaces leveled.  Otherwise, you’ll just have to install gaskets later on if you want to get rid of that ‘ticking’ sound (it’s usually not valve noise).  If you DO install gaskets, get locking manifold bolts, and DON’T over-tighten (just snug them down), as that will typically crack the ears.  After a few heat cycles, you can tighten (snug) again if leaks occur (don’t forget to unlock the bolts first), but the aluminized gaskets seldom need it.  Make sure the gaskets are trimmed so they match the port openings.
By paul2748 - 3 Years Ago
If your not reinstalling the original manifolds, either have both mating surfaces trued or use  a gasket.  You don't know how true the new manifolds are and if there is warpage of the head mating surface.

I use gaskets.  I always tighten them just like an intake or head.  Start from the middle and go outwards.  First round just tighten all of the bolts to snug, then go over them to tight.
By KULTULZ - 3 Years Ago
IMO ...

My experience has been that the gaskets tend to promote the manifolds cracking and/or breaking more quickly due to the gasket separating the two and there being a greater heat differential between the head and the exhaust manifold. 

TED


Composite gaskets are asking for a failure. They allow different heat expansion rate (and expansion/contraction) between the two different components. If you are worried about a possible leakage, FORD offered steel shim gaskets with heat shields for later FYB truck engines (I think VICTOR still carries them).

Good quality hardware, thread-loc and possibly mechanical locks if you don't mind the non-stock look.

Again, IMO ...

http://forums.y-blocksforever.com/uploads/images/705d00ae-4bf6-4421-a570-8867.jpg


By DryLakesRacer - 3 Years Ago
On mine the last cap screw on the fire wall end needed a header style bolt. 3/8” or 7/16” head and large flat flange.
I worked in the power plant industry for over 40 years and quickly found our smaller steam valve packing adjusting bolts were 3/8-16 with a 3/8” shoulder, flange, And 7/16” wrench head. After outages in the scrap bin I removed every bolt I could find. The greatest exhaust manifold and header bolts ever. Headman also had smaller OD lock washers that were thicker. Don’t have any of them left..
By PF Arcand - 3 Years Ago
Just for info; What about the Copper exhaust gaskets that were available some time back?  They were advertised in Y-Block magazine at some point in the  past.. 
By KULTULZ - 3 Years Ago
Just for info; What about the Copper exhaust gaskets that were available some time back?  They were advertised in Y-Block magazine at some point in the  past.. 

  Paul


I had forgotten all about these.

THANX for the wake-up call.
By Ted - 3 Years Ago
PF Arcand (3/17/2021)
Just for info; What about the Copper exhaust gaskets that were available some time back?  They were advertised in Y-Block magazine at some point in the  past..

I use copper exhaust gaskets on the dyno and they do have a tendency to leak when the mating surfaces are not perfect.  The copper gaskets do not allow enough varying conformity to the surfaces and are simply too hard in which to compensate.  I have tried annealing the copper gaskets to soften them up but haven’t had much success with that helping.  But clean up is minimal and the copper gaskets do tend to last forever.
By 2721955meteor - 3 Years Ago
KULTULZ (3/4/2021)
IMO ...

My experience has been that the gaskets tend to promote the manifolds cracking and/or breaking more quickly due to the gasket separating the two and there being a greater heat differential between the head and the exhaust manifold. 

TED


Composite gaskets are asking for a failure. They allow different heat expansion rate (and expansion/contraction) between the two different components. If you are worried about a possible leakage, FORD offered steel shim gaskets with heat shields for later FYB truck engines (I think VICTOR still carries them).

Good quality hardware, thread-loc and possibly mechanical locks if you don't mind the non-stock look.

Again, IMO ...

http://forums.y-blocksforever.com/uploads/images/705d00ae-4bf6-4421-a570-8867.jpg




By Ted - 3 Years Ago
Talking about the use of exhaust gaskets is analogous to talking about religion, politics, or the brand of oil that’s being used.  You can always count on a spirited discussion when any of these are brought up.
 
First and foremost, some form of composite exhaust manifold gaskets are typically included with engine rebuild kits although most factory engines come with just a metal to metal fit between the exhaust manifold and the head.   These composite exhaust manifold gaskets are not to be confused with some of the steel shim exhaust manifold gaskets included with factory industrial or heavy duty engines.  Because the composite gaskets are included in the gasket sets, most people feel obligated to use them.  In short, exhaust manifold gaskets do compensate for imperfections or warpage that takes place over time.  Removing an exhaust manifold for any reason does bring exhaust manifold deficiencies to the forefront and the gasket is the cheap fix.  The more expensive fix is machining the exhaust manifold and/or cylinder head exhaust surfaces to get those back to where they will seal again.  $20 for a set of gaskets or $150+ for machine work is usually the deciding factor here.
  
The question at this point becomes just how tight to tighten the manifold bolts when using a gasket.  It’s obvious that using the original manifold to cylinder head torque spec is not going to work as excess torque at the flanges with a composite gasket in place is going to deform the manifold and especially more so at the ends of the manifold as in the case for the Ford Y.  As has been brought up, fasteners with locking capability or lock washers helps where the bolts cannot be torqued to their stretch limits.  The key here is to not over-tighten exhaust manifold bolts when gaskets are being used.
  
But back to why the factories do not use exhaust gaskets.  I had this conversation with a factory engineer several years ago and while the factory uses all brand new parts where sealing is not an issue on a new engine, there was a problem with the temperature differential between the cylinder head and the manifold.  Using no gasket or a metal to metal fit allows part of that excess heat or temperature differential at the flanges to be redistributed back to the cylinder head casting thus allowing the manifold to run cooler and slow down the propensity for cracking at the flanges.  Whereas industrial equipment may run steady state for hours on end where a varying temperature differential is not a problem, an automobile on the other hand does see varying temperature changes at the exhaust manifolds which brings forth issues not seen on industrial equipment.  For an automobile, the amount of heat being put back to the cylinder head casting does not have a significant effect on engine cooling but does lower the temperature of the manifold just enough that cracking due to excessive expansion/contraction of the cast iron is minimized thus slowing down any propensity for cracking.  The hotter an engine runs, the more the problem.  While I don't have the data to back it up, I suspect engines in the lower latitudes or mountainous areas have more cracked exhaust manifolds than those where the temperatures are cooler or the engines are not required to run as hard (climbing mountains).
  
My own experience over the years has exhaust manifolds using gaskets cracking more frequently than exhaust manifolds fitted to the engines with no gaskets.  Some of this breakage can be attributed to the age of the manifolds while other breakage can be traced to over-tightening of the fasteners.  The exhaust manifold design itself can also be a factor and especially where end cylinders on the same manifold fire consecutively.
 
Feel free to shoot holes into any of this or at least take pot shots at it.
By Hoosier Hurricane - 3 Years Ago
Ted, there is another possibility why the factory did not use manifold gaskets.  Cost.  Since new engines with new manifolds didn't really need gaskets, why spend the money for gaskets?  Did your engineer mention that in your conversation?
By 312YBlock - 3 Years Ago
Years ago I smelled exhaust gas while driving my 55, it was annoying, you take someone for a ride “nice car but PU”. Fuel mixture not being an issue I bought EM gaskets as I could smell exhaust when I popped the hood. I installed the gaskets and being ignorant of any torque limitation I torqued them to factory specs. I first turned all the bolts finger tight and then followed the documented tightening pattern a little at a time over and over again until I was at spec, that was at least 10 years ago. These are the original exhaust manifolds with God knows how many miles on them. They don’t leak, they haven’t cracked. Ceramic coating the entire manifold including flanges will deflect heat away from the heads. Weather you ceramic coat the EMs or not, installing them without gaskets is a win win as the temperature of the EMs will be reduced either way. But hay, I enjoy a Manhattan with Luxardo cherries, others like Maraschino cherries, we can argue the cherries but know one argues the taste of what’s in the glass, bottoms up 🍸.


By 1/8cavman - 3 Years Ago
2 cents from a new guy. I think Ted Eaton covered it all, except the cost factor, which was brought up by Hoosier Hurricane. Saving dollars-cents is the beans-counters job. Also, I believe no one has addressed intake manifold exhaust leaks. Were there intake gaskets with the metal sealing at the heat transfer ports originally used? Also how are the aluminum intake manifolds with the heat transfer ports holding up? Do they use the the metal gasket section for the heat trans ports and regular gasket material like the iron manifolds? One more, Headers, and which ones address flange leaks better than others. I have stirred enough and am out of ammo. Now on to the cooling subject!   1st Cav Man
By DryLakesRacer - 3 Years Ago
Since many questions are being asked and answered by experience; I believe Ted stated that the EM will be cooler if directly attached to the cylinder head by heat dissipation. If this is true with the engine running hotter? And is it better to have no gaskets after an engine has been shut down to cool?
The manifolds on my engine are not original to the car or engine and as far as I know the surfaces of either have not been machined. The outside of them are coated and I run the Best brand gaskets.
I also needed to add heat defectors to the master cylinder I add because if did not like the temp when I checked. The standard car did not have one and the Thunderbird did. I installed the Thunderbird one in a longer form and attached silver reflecting tape to the bottom. It did drop the temp of the MC 15*...Any thought are welcomed..
By PF Arcand - 3 Years Ago
Cavman: If I understand your question re intake gaskets properly?.. Not sure originally on cars, but the Truck heat crossover hole, in the intake gaskets, I believe  had a restricted hole with a metal edging in it. They can be used on car engines to partly restrict heat under the carb..  
By 2721955meteor - 3 Years Ago
HAD FORD WHEN THEY BUILT YBLOCK ENGINES USED DECENT MANIFOLD HARDWARE(THEY USED GARDEN VERYTY GRAD ATBEST 5
HARDWARE THIN FLATS. RESULT WAS THES ENGINES  WHER KNOWEN IN BC CANADA AS LEAKERS.
MY EXPERIANCE WAS CARS FORKLIFTS,LUMBER CARRIERS. TRUCKS MOSTLY INDUSTRIAL. THE BEST SOLUTION WAS GASKETS, PROPER GRADE 8 CAPSCREWS,HARDENED FLAT WASHERS(NO LOCK WASHERS) L/W WHER TO NAROW AND THE HEAT REMOVED THE SPRING. INDUSTRIAL GRADE 8 HARDWARE IS ELASTIC AND WILL STRECH WITH  HEAT CYCLES IF OVER TORKED  YOU LOSE THE  STRECH. MY FINAL PREECHING ON THIS  TOPIC EVEN THO ACTION ON THE SITE HAS SLOWED A BIT. I ENJOY THIS SITE SUCH A WIDE SCOPE OF INTELEJENT GUYS
By Tedster - 3 Years Ago
What I have observed over some years, not just with exhaust manifolds, what the factory or OEM did or didn't do, their procedures or what they could get away with are not necessarily going to work for the DIYer for several reasons.

Another factor is the way some approach tightening fasteners, (nuts and bolts, wheel lug nuts, flanges, water pumps, intakes, carburetors, etc) and here we very often see the real problem. When everything is nice and new, mating surfaces are clean, and true and flat, or near enough. Fast forward 30 or 50 or 70 years, surfaces aren't "true" anymore. The tendency with something that leaks is to reef it down a little more. Or a LOT more. But in the case of warped mating surfaces, it will likely leak no matter what, no matter how tight the bolts or nuts may be.

If you look at exhaust manifolds, the spec is 23 to 28 pounds.. Nice and firmly snug. Tighter is not better! A big thing people overlook with torque specs, is once the component has been properly torqued, they must be checked after so many miles (or heat cycles) and re-torqued (if necessary) to spec until they stabilize at that torque. They will often "loosen up" for a period of time, but they will stabilize. Exceeding the torque spec value, in hopes of avoiding extra time or labor, is likely just going to ultimately result in cracked or broken parts, and you won't have saved any time or money anyway. When I installed Rams Horn manifolds on my Y, I used "gaskets" insofar as the accompanying special aluminum heat shields used with Rams Horn, they stand up even with the top of the valve covers, and the reason here is (I think) to keep excess heat away from valve springs or guide seals, or maybe coking up the motor oil. But it took a while for those manifold bolts to stabilize, maybe 3 to 5 cycles.

The Shop manual has all the torque specs, it isn't a bad plan to go over everything on the engine and transmission and make sure it's snugged up. I find this oddly satisfying, but, then I'm pretty weird.
By 312YBlock - 3 Years Ago
Hi all, I originally started this thread with the question “ Are exhaust manifold gaskets necessary on a 312?”. I bought a new set of EMs, had a machine shop true the flanges on a belt sander, had them ceramic coated and installed them without gaskets with a “very thin” coating of permatex orange high heat RTV silicone per Ted. I finger tightened the bolts, then snugged them up with a 3/8 ratchet, from the center out, then tighten them up with the ratchet; next it put a torque wrench on them and found I was at 20 to 22 lbs already (shop manual calls for 23 to 28 lbs) I stopped there and fired it up; no leaks, one and done. I will re-torque after a few more miles and publish my experience with the ceramic coating in a future post but when it comes to torque, as the man said “tighter is not better” it’s all about the fit 🚗.