I have 76 Pontiac Ventura, I am at the point were it is time for an engine. I have a 75 Pontiac 400 bore 30 over and 6x heads that were all ready assembled. From what I understand from the person that I got it from, that it has a 9.72:1 with pop piston( what every that means)??

I have talk to other people and they said to dump the motor and get a 350 because Pontiac parts for the motor are to hard to come by and that 350 would get me more power in the long run.

My question is that I have a  money in this 400 and don't know if I can get enough power from it  with out putting in a rough cam and running as a drag car

 I would like this to be a every day driver with some power.

I would keep it pontiac powered if I were you.  The small block chevy engine swap is kind of the easy way out.

Your pop pison may be a pop-up piston.  Part of the piston may be raised above the surface to reduce combustion chamber volume.  Pop-ups are sometimes called domed pistons.

Tom

You have two chances of making more power with a small block Chevie than you can with a 400 Pontiac. They are as follows - slim and none. Keep the 400.  

Id keep the 400 there are plenty of great parts available, youve got more displacement and of course it's a poncho in a poncho.  

Keep the Poncho---more cubes,classic Pontiac power, there are Great parts availible & being more of a torque motor, great for the street. If your friends say it can't/won't run ask them when was the last time they saw a slow 68-70 GTO.  

With the availabilty of parts for the pontiac motor, i would keep it that way. Plus, it will make very good power, just look at the 350 story that CC printed  a while ago, it made 500+hp, the 400 would be even better. While a 455 may make more torque, the 400 revs quicker. Just keep an eye on the cam, as really high rate valve springs can cause a blowout of the valley area.