TommyTipper Posted October 16, 2019 Share Posted October 16, 2019 Hi guys, currently rebuilding my Mack 470 and wondering if anyone knows which way the fire rings go when pressing around the liner on the block? It's a PAI kit and doesn't state which way they go as 1 side is concaved and the other is flat. I'm assuming it's flat side down but would like to know 100%. Thanks Tom Quote Link to comment Share on other sites More sharing options...
fjh Posted October 16, 2019 Share Posted October 16, 2019 I have always installed the fire rings sharp side down as long as the rings are the new style none stepped rings! It’s never failed me yet! Quote Link to comment Share on other sites More sharing options...
TommyTipper Posted October 16, 2019 Author Share Posted October 16, 2019 2 hours ago, fjh said: I have always installed the fire rings sharp side down as long as the rings are the new style none stepped rings! It’s never failed me yet! Do you mean with the concave facing down? Quote Link to comment Share on other sites More sharing options...
Mackpro Posted October 16, 2019 Share Posted October 16, 2019 We always did flat side down. The weird stepped liners were pre-ETECH only best I remember. I think it was 1991/1992 was when they stopped the stepped liners Quote Link to comment Share on other sites More sharing options...
fjh Posted October 16, 2019 Share Posted October 16, 2019 (edited) 5 hours ago, TommyTipper said: Do you mean with the concave facing down? honestly I don't think it matters however, yes the convex up facing the head ! the sharp side facing the liner that way the ring stays put better! AND just a word to the wise you should have measured your liner height (protrusion )! correct ? You needed to be trying to achieve at least 24 thou Bottom spec for best results on a 400 plus HP engine !the book low spec is TOO low for anything over 400! Edited October 16, 2019 by fjh Quote Link to comment Share on other sites More sharing options...
Mack Technician Posted October 16, 2019 Share Posted October 16, 2019 44 minutes ago, fjh said: honestly I don't think it matters however, yes the convex up facing the head ! the sharp side facing the liner that way the ring stays put better! AND just a word to the wise you should have measured your liner height (protrusion )! correct ? You needed to be trying to achieve at least 24 thou Bottom spec for best results on a 400 plus HP engine !the book low spec is TOO low for anything over 400! Low spec or top spec? We tried hard to hit the top spec/max protrusion to get the extra sleeve crush and fire sealing in high HP range. Above 400HP you tend to have a hopping head. Quote Link to comment Share on other sites More sharing options...
fjh Posted October 17, 2019 Share Posted October 17, 2019 (edited) 10 hours ago, Mack Technician said: Low spec or top spec? We tried hard to hit the top spec/max protrusion to get the extra sleeve crush and fire sealing in high HP range. Above 400HP you tend to have a hopping head. As I mentioned shooting for 24 is best ! top spec is 28 I believe we have run them at the top end as well however never experienced head hop or shuffle.we also use hi tack on both sides of the gasket with no issues! Edited October 17, 2019 by fjh Quote Link to comment Share on other sites More sharing options...
TommyTipper Posted October 17, 2019 Author Share Posted October 17, 2019 11 hours ago, fjh said: honestly I don't think it matters however, yes the convex up facing the head ! the sharp side facing the liner that way the ring stays put better! AND just a word to the wise you should have measured your liner height (protrusion )! correct ? You needed to be trying to achieve at least 24 thou Bottom spec for best results on a 400 plus HP engine !the book low spec is TOO low for anything over 400! Yea that's a what I figured. Jus really wanted to make sure it was right as it seems every truck has a different set up. Thanks for that Quote Link to comment Share on other sites More sharing options...
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