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Old 12-22-2017, 04:30 AM   #1
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Default exhaust manifold gasket design?

can anyone tell me why are the Manifold exhaust gaskets separated from one another. why are they designed that way, what are the benefits of not being one unit.
its not like you can purchase one if only one was compromised, you have to order the gaskets in a set of 4....
does anyone have a theory on this...?
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Old 12-22-2017, 05:15 AM   #2
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Swedish engineers, speculated that an eccentric group of car enthusiasts would drive old Swedish cars long beyond their "planned obsolescent(s)?", and so designed them that way to create these types of questions.
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Old 12-22-2017, 05:56 AM   #3
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the exh manifold and head get very hot , i guess seperate exh gaskets allow for some heat expansion. also, the cast iron manifold and the aliminium head expand at a different rate.

If you take a closer look at the exhaust manifold you will also notice that some holes are bigger then strictly necesary, and that Volvo used some special (concave?) washers to mount the manifold. Designed to allow some heat expansion.
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Old 12-28-2017, 02:07 AM   #4
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Originally Posted by BrodeeSmith View Post
...why are the Manifold exhaust gaskets separated from one another....
Catalytic converter operates in an optimum heat range. There would be less heat emitted in exhaust gases with individual cylinder exhaust gaskets. But, maybe yes, maybe no here...a four cylinder engine does produce more exhaust heat than a 6 or 8 cylinder engine in typical driving situations.

Quality control might be better with individual gaskets...in those early days. Exhaust gaskets are designed for sealing, in a tough environment.

I believe carburetor based Volvos (B16/B18/B20) all used a complete exhaust gasket. When intake and exhaust manifolds are bound together, this heats the intake to prevent intake icing conditions.

On the far-side, I'm not aware of Bosch's EFI programming, but consider this tidbit about fuel enrichment at higher operating temps,

"Another benefit, he says, occurs at high engine loads where exhaust gases are so high, they risk compromising the life of the catalytic converter. Cooling these gases with coolant, Fenske mentions, prevents the engine control unit from having to dump more gas into the combustion chambers to lower exhaust temperatures. This means a staggering 20 percent better highway fuel economy on the 2017 VW Golf Alltrack he was driving. Not to mention, the lower CO2 emissions that go along with that."
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