GeorgeCostanza Posted April 16, 2010 Share Posted April 16, 2010 Hi everyone I am thinking about purchasing a 1990 SM. It will be my first SM but I am not new to racing. The car I am looking at is a BSI built spec miata that has been well cared for and overall it passed the PPI. It has the following results for compression: 1 - 185 2 - 180 3 - 180 4 - 190 leak down: 8% 8% 10% 12% I did not find much discussion about leak down results on the forum through the search function so I thought I would post it here and see what you think. The engine was built two years ago by a reputable SM builder in Florida. Quote Link to comment Share on other sites More sharing options...
krystar Posted April 16, 2010 Share Posted April 16, 2010 are those leakdown numbers average thru whole crank rotation? or only at a single crank position? but yea those numbers are good Quote Link to comment Share on other sites More sharing options...
kbrew8991 Posted April 16, 2010 Share Posted April 16, 2010 >10% leakdown isn't that good iirc Quote Link to comment Share on other sites More sharing options...
Shortcutsleeping Posted April 17, 2010 Share Posted April 17, 2010 Who is doing the test and what are the test procedures and what equip are they using? For starters: http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html Much like a dyno, through different techniques I can vary the #s pretty wildly. Costas cars and such... Quote Link to comment Share on other sites More sharing options...
jthill Posted May 27, 2010 Share Posted May 27, 2010 Not good numbers. But the good news is that an inexpensive head refresh can usually fix this problem. Quote Link to comment Share on other sites More sharing options...
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