| Van, you probably need a little tighter thoat and/or backbore on that mpc. You need to really play around with mpcs to find a match. If you can't find a better match, then you probably shouldn't keep the horn.
Let the excitement wear off and then try a few other mpcs (a 68MD is pretty big). 3C is a good place to start, or a GR3 or 66M or 66MX.
Dave |