Quote Originally Posted by Poil336 View Post
are the DOHC 3.4's interference motors?
The '96 - '97 are. The '91 - '95 are non-interference, but juuuuust barely. Still very, very tight clearance, enough so that there have been many reports of valves being bent when the belt goes at higher(and sometimes not so high) RPMs on various GM 60° V6 related forums.


Taken from w-body.com alone with just a quick search:

"while the 3.4L is not designed as an interference engine, it has happened that when the timing belt breaks or slips, the pistons can hit the valves. ther is only .010" designed clearance between the valve at full lift and the piston at top dead center. That is how my GP was when I got it. 6 bent valves, timing belt broken."

"My 95 GTP sent a valve through a piston due to the belt snapping."

"I think there is someone here on the list who had a bent valve due to carbon deposits in the cylinder."
"Yep, that would be me!"