What's up champ, thats too bad about your motor. Yes, these are my suggestions for your 91 Si. I have a 91 Si Civic also. This what I recommend. Get you a B16A1 w/ cable tranny. I have a 1st Gen in mine w/ DC sports header, custom short ram intake & a Thermal Research Development exhaust. You'll pay around $3200 for swap, not including exhaust & header.. Alot of people would tell you to get the B18C1 Gsr because more tq. etc... You'll love the power / 8200 redline 160 hp, 111 tq. Good luck.....