Chevy Cavalier 2.2 L4 Ecotech Dirt Car

I have a 2004 Chevy Cavalier with a 2.2L L4 motor
and an F23 5 speed transmission I've built into a
dirt track car. It's my rookie season and I'm looking
for tips and have some questions. My car was
running pretty good but I would rev limit a little
before I got in the turns so the computer "might"
have been turned to 7200 rpms from 6500 which
the stock heads should hold and they have. How
ever since I blew one motor throwing the piston
collar out the side of cylinder 3 and part of the rod
out of the oil pan. So I got another motor from a
junk yard pulled the valve cover and pan and motor
looked good had 119xxx miles on it. Put it in and
same thing. Piston collar in cylinder 3 ejected out
the side of the cylinder at the bottom. So this time I
took the timing chain cover off and checked the
tensioner and chains. The timing chain was snug
and in place however the chain to the balance
shafts seemed to have some play by the tensioner.
Little confused because I've found out that
tensioner becomes pressurized when running so I
dont know if that's the problem or if anyone has
any ideas or explanations I would greatly
appreciate it. Also we can't run aluminum radiators
they have to be a stick application so I was
wondering if there's a bigger radiator from another
vehicle that would swap over. Thanks ahead for
any input