I posted part of this in my build thread but I wanted to make a separate thread to help anyone else who is using this head. When I got this head I bolted it on and ran it without checking anything first. I figured whoever designed it knew what they were doing (I've learned to never assume that in this hobby).It felt like LESS compression than my stock slant head. Now I know why. After looking at it when I tore down my motor I see the plug was no where near deep enough. It's this head from MZMiami http://www.ebay.com/itm/MOTORIZED-BI...item4198654527 This is with the stock equivalent plug. I took the picture with an NGK BR6HS installed. You can't even see it down in there. This would seem to be where my low comp was coming from. This is with an NGK B6ES installed. "E" is longer than "H" for more reading on those plug numbers http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf Hope this helps anyone else using this head or facing a similar problem.