Hi Habib,

I agree with Peter as well but I put together some explanations of why you have what you have.

It sounds like you might have some warped flange on either side of the fitment or both at the same time. I can say that in all likelihood the bolts were overtightened in an attempt to stop leakage and the continuous heating did a number on all of it.


This has nothing to do with the manifold being bolted previously to the head.
You must have that thing flat and on location.
I believe you have done it correctly to get those eight studs coming out of the head and through exhaust manifold first.
Evenly tightened down flush always works.
The most important thing going on here is to be sure it’s not leaking from that work. Using a paper drinking straw you can feel for a n exhaust leak.
Push it around the runner connections of the head with the engine running.
It you feel or see it get wiggled by escaping exhaust gases you found the noise leak.
If you remove the manifold now it you will to replace that long gasket again.
Especially if you ran the engine for some length of time to form or set gasket material. So leave it alone at this point.


What I really suspect is that the outer edges of each others flange surfaces are hitting.
Or the studs or bolts are bent crooked or not perpendicular coming out off the exhaust manifold.
They may be bent causing the fasteners not to have enough clearance around each hole to the mating pieces.
The holes make the flange plate into bendable ears and the hole itself in them can bite the fasteners. Binding occurs long before the gasket touches down.

You need to get things straight or parallel to each other before bolting up anything. One gasket is only made to seal between two nice flat surfaces.
The thinner the space the less likely of exposure to cause a flow to burn through.
I have never studied this area as I do not ever recall having to remove that connection on any of my cars in particular. I only have had to work from the catalytic converter backwards with mufflers.
Oh shoot, now I have probably just jinxed myself?🥴.
If you brag about getting away with something a big mallet seems to come out from nowhere to thump you for saying it.😬

The whole affair of the exhaust system, from that joint point backwards is purposefully made to be all adjustable by length or rotation.
So, wiggling the pipes and hangers should get it aligned.

Get the exhaust system to fit together as well as you without a gasket in there.
You must see even amounts of daylight across the faces.

The holes in the flange make those ends weaker and thusly will keep the gasket from seating flat.
Get them together as much as possible so that the gasket will have less to do.
Finding which of the three corners is bent worse is the key.
It may take some grinding to knock them down to get clearances. Try Not to weaken the thin plate flange anymore than you have too.
The massiveness of the CAST IRON manifold should have kept it flatter so don’t mess with that. If studs are bent, replace them and I think you said you tried that.

Steel is lighter and cheaper compromise for the rest on the system.
Imagine how heavy it would be using cast iron be all the way back to the rear bumper?
Stainless Steel exhaust manifolds and pipe are around today but technically they bring aboard their own issues but have been designed out for the most part.
One is that they can glow more readily so heat shields are needed to interrupt the extra infrared transmission to something very near.
Steel revolutionized the making of coal and wood stoves back in the early 20th century for better heat to air convection


On American domestic vehicles they use a fat or a thick beveled “donut” affair that were reasonably crushable but still used an inner steel ring.
In fact, they are nicknamed “donuts” not an “exhaust pipe gasket” as that was too long to say quickly.
They used to be made of graphite and asbestos.
I think it mostly fiberglass strands as even lead has been banned along with other metals like antimony.
Toothpaste tubes used to be made of antimony metal. The days before plastics. Now we wonder about plastics.
I know this as my uncles casted their own firearm bullets as that stuff made them have a smoother finish . That might be called a cheap recycling method today. 🤫

Just one of many Amalgamation’s of metals conjured up.
Another case where this technology was used in filling tooth cavities back 50 or 60 years ago?
Some like me are lucky to be alive this long but I had good dental plans.
I grew up with that stuff in my mouth. Several years ago dentist desperately want you to get rid of them.

Good luck with getting a good fit up under there but don’t try any space goops against hot gases! 😵‍💫 you couldn’t afford it anyway.

Thanks for reading my “passing time” event.
Phil

I made a reply earlier but it doesn't seem to have posted. I will repeat that thought:

I don't think you will ever get a better seal between the head/gaskets/manifold than you have now with new gaskets and proper torqueing. I would not loosen the manifold at this point. I don't think there is anything to gain if you have free movement of the downpipe.

While I have read that manifold bolts can be retorqued after several heat cycles that would be done one fastener at a time to prevent movement of the initial assembly position of the gaskets in relation to the other components.
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Any twenty minute job is just a broken bolt away from a three day ordeal

Peter,
No apology necessary.
Randy
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Any twenty minute job is just a broken bolt away from a three day ordeal