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Head gaskets doubled up.
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Paul Hettick
Posted 2021-03-16 9:49 AM (#609942)
Subject: Head gaskets doubled up.


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Recently purchased a 318 powered plymouth with a freshly rebuilt engine. Massive vacuum leaks at intake. Removed that and found hasket sealer on the metal intake gaskets. Have not pulled the heads but the edges of the head gaskets are visible and it appears there is 2 gaskets for each head. Why the he k would someone do this? Any ideas?
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wizard
Posted 2021-03-16 10:39 AM (#609945 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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Too high compression for standard fuel? Oldsmobile had thinner head gaskets if the J2 (3x2 carburetors) option was mounted by the factory.
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LostDeere59
Posted 2021-03-16 2:15 PM (#609965 - in reply to #609945)
Subject: Re: Head gaskets doubled up.



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I'd check everything about that engine very, very carefully.

Doubling head gaskets was something done with old steel shim gaskets to reduce compression a bit. Modern composit gaskets won't tolerate that kind of application.

My concern is if someone did that, how many times did they have the heads off? Another concern - obviously they didn't get the intake properly sealed, so what else did they screw up?

I'd would wonder if the doubling was because they removed too much material from the block when decking it, creating a piston/valve clearance issue, or from the cylinder head potentially causing the same issue, or excessive compression.

With todays gaskets and machining capabilities there's no GOOD reason for that kind of installation . . .


Gregg
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Mopar1
Posted 2021-03-16 6:02 PM (#609985 - in reply to #609942)
Subject: RE: Head gaskets doubled up.



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Paul Hettick - 2021-03-16 8:49 AM

. Removed that and found gasket sealer on the metal intake gaskets.
To get metal gaskets to seal you spray them with aluminum paint. Lay flat so there's no runs & let dry well before installing.
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Powerflite
Posted 2021-03-16 10:20 PM (#610002 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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Most likely, it is to compensate for too much material removed, that now allow the intake to mount. Without them, the intake may be too far off to mount to the heads. If it works, I wouldn't touch it. that's a major can of worms that you would be digging into.
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22mafeja
Posted 2021-03-17 1:03 PM (#610029 - in reply to #609942)
Subject: RE: Head gaskets doubled up.


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Probably there has been too deep corrosion on the heads , therefore machined away too much and now the intake manifold sits too high.
I would mark how the intake sits and remove it and machine off what is necessary. And like Nathan suggested leave the double head gasket
untouched if it works.
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Paul Hettick
Posted 2021-03-17 5:09 PM (#610046 - in reply to #609942)
Subject: Re: Head gaskets doubled up.


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I bolted it back together this morn with fellow pro intake gaskets. Runs better but still wont idle smoothly. The carb base gasket only makes contact with the outer circumference of the carb base. Shouldn't the ports be segregated by the gasket?
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60 dart
Posted 2021-03-18 12:04 AM (#610059 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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metal intake gaskets ?
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Paul Hettick
Posted 2021-03-18 7:49 AM (#610072 - in reply to #609942)
Subject: Re: Head gaskets doubled up.


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Yes metal. Thought I would roll the dice and see how it runs with the new gaskets. It's better but still runs rough through all rpm ranges
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wizard
Posted 2021-03-18 8:20 AM (#610073 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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Does the engine responds to the mixture screw or not? It's not so important that the carburetor gasket seals over the total area, but I would fix it.
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Paul Hettick
Posted 2021-03-18 6:38 PM (#610103 - in reply to #609942)
Subject: Re: Head gaskets doubled up.


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Yes the air mixture screws when screwed in will kill the engine. Backing them out will smooth out somewhat but still rough
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60 dart
Posted 2021-03-18 11:40 PM (#610115 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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so its an la 318 -----------------------------------------later
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Mopar1
Posted 2021-03-19 6:48 AM (#610122 - in reply to #610002)
Subject: Re: Head gaskets doubled up.



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Powerflite - 2021-03-16 9:20 PM

Most likely, it is to compensate for too much material removed, that now allow the intake to mount. Without them, the intake may be too far off to mount to the heads. If it works, I wouldn't touch it. that's a major can of worms that you would be digging into.
Actually doubling the head gaskets would move the heads up and out, slightly increasing the distance between heads,
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Paul Hettick
Posted 2021-03-19 4:48 PM (#610150 - in reply to #609942)
Subject: Re: Head gaskets doubled up.


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Yes it is an early 318. The intake leaks moved from the bolt holes when gasket sealer was used to the top edge, front to back with new metal gaskets and no sealer. Any way to check if the heads have been milled beyond spec without tearing the whole mess apart?
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60 dart
Posted 2021-03-19 5:38 PM (#610152 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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if the heads were shaved i'd doubt the intake would fit at all , unless the intake was shaved also . first in order would be to
replace the intake gaskets to fiber gaskets ------------------------------------later
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Paul Hettick
Posted 2021-04-18 5:20 PM (#611206 - in reply to #609942)
Subject: Re: Head gaskets doubled up.


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Thanks Chuck had the intake surfaced and used fiber gaskets. All good now.
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60 dart
Posted 2021-04-18 11:58 PM (#611219 - in reply to #609942)
Subject: Re: Head gaskets doubled up.



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cool!
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Stroller
Posted 2021-05-10 10:17 AM (#611866 - in reply to #609942)
Subject: Re: Head gaskets doubled up.


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If the head gaskets were doubled it would change the angle of the intake mounting not also to mention raising the height. As the to carb I'd pull the carb and intake back off and grab a file.
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