Originally Posted by MalibuMike
Okay I'm getting a lil better understanding how it (bore sizes) work, but I was "TOLD" the largest a 454 could be bored is .060... Neways, how do I build the motor for torque? Keep in mind guys, like I stated in an earlier post "this is my first time dealing with a big block" so be patient with me. As of now my motor has 336781 heads, would I be better off using these or swapping them out for a set of rectangle port heads?
Keep the 781 heads. The 781 head is one of the most popular (along w/the 041 head) to use on a torquey 454 BBC.
Rectangle port heads are for high rpm use. The crossover point where the rectangle ports pulls ahead of the oval port heads at a higher rpm and lift than you'll be needing, so the rectangles are not for you.
You might want to consider adding 2.19" x 1.88" valves if you have the budget- but for a torque engine this isn't mandatory. Be sure to pay attention to the valve spring installed height so there's enough spring pressure and clearance. If you do get bigger valves, you should look at using 0.100" longer valves to have plenty of room for setting the installed spring height.
781 heads are right about 122cc chamber size. That means you'll need a domed piston to have any sort of compression. Flat tops will have you at or below 8:1.
More: 781 vs. rectangle port BBC heads