My boy ran an SR for a couple of years. It was over 20 yrs old when he got it. Bullet proof wee engine with absolutely no mechanical issues. The ECU, now that was a different matter, he went through 3 of those (although we were replacing 20 odd year old part with other parts the same age....)
If you keep breaking valves I would suggest that is something you or a PO have done to set the timing way out
Welcome to the forum btw, and a great user name