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windwaiver · Joined: 08 Feb 2009 Posts: 69 Location: reno, nv

Ok, is it common knowledge to always have the head resurfaced everytime you remove it? I want to replace the rings and mains in this car, I had the head done about 10k miles ago. oh its a 82 924 NA.
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77.5 924 NA
81 924 na (great parts car)
82 924 NA
87 944S this is gonna cost
00 K1200LT

If i had a nickel for everytime I screwed up.......

!tom · Posted: Thu Jan 21, 2010 2:26 am Post subject:

Only if it needs it.

Check the head for flatness (with a straight edge). If it isn't flat, it needs to be machined. If there's been a head gasket failure, it may need to be machined (depending on the nature of the failure).

If the head already meets flatness specifications, then machining it is both a waste of the head's life and your money. It might be good for the economy though.
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78 924 NA
5-lug

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

+1^
To emphasize Tom's point, these heads are notorious for not having sufficient head height, so only machine it if you absolutely must. When I did my top end rebuild on the NA after its head gasket failure, I didn't need to machine it. But my failure was a very gradual one, not a catastrophic blow out. YMMV.

Here are the specs:
Permissible unevenness of mating face: 0.1 mm
Max. reworking depth 0.4 mm
Peak-to-valley height = 0.015 mm
Head height = 139.55mm
Page 8 of the 924 Tech Specs booklet, complete with illustration of how to measure.

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erstwhile owner of just about every 924 variant ever made