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How smooth does surface of head gasket have to be

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You don't reuse head gaskets...ever.
New head gaskets are not that expensive.
get a new set of head gaskets, some gasket cement, and do the job right.

Posted on Apr 12, 2015

  • AmyZepeda JeffHackleman

    I have a new gasket wasn't sure how smooth it had to be. Thank you :)

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Of course you mean the surface of the head and block. This should be about 30 microinch Ra. However this is quite difficult to assess without specialist equipment.

First remove all traces of the old gasket and any cement which may have been used, with razor blade scraper, a hard plastic scraper, a nylon scouring pad, or similar. Aluminium heads especially need care.

You may find a gasket remover spray of use, but be careful it is suitable for aluminium.

Of greater importance is measuring the flatness of head and block surfaces with a straight-edge and feeler gauges.

http://www.newtonnet.co.uk/coupe/service/xml/graphics/a5/a5em034a.gif
http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0996b43f/80/20/0d/a7/medium/0996b43f80200da7.gif

The average spec for a 4-cyl cast iron block and alloy head is max 0.002" total non-flatness in any direction. If this is exceeded (probably by the head) have the surface skimmed.

Posted on Apr 12, 2015

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Completely smooth, u need to remove all traces of old gasket & goo by scraping it off & then polishing both surfaces till smoother than a babys bottom before fitting new gasket & tourqing down correctly, not a job to be done by an amature, usually the head would need to be skimmed also if the engine overheated incase it has warped, it could even be cracked into a waterway which would render it U/S anyway, get it checked by a pro?

Posted on Apr 12, 2015

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