How important is it to line bore and balance your motor? I am in the prosess of building my first motor, and have chosen the 454 big block, it has been bored to .040 and has flat top pistons, I am planning on going with the 100cc heads, which should give me around 9.2 :1 compression. I am also going with elect. water pump, a complete roller cam and rockers, and top it off with a 800 cfm carb. I am not possitve, but I think I should be around 540hp when I am done....thanks  

The line bore better be checked by a machinist. If the engine hasn't had a lot of time it may not need to be done. Are you using the stock crank? stock rods? If you are using stock rotating components then the pistons you're using better be the same weight or slightly lighter than the stock pieces. If you meet all of this criteria then you probably could also skip the balance...

Your horsepower goals are awfully optimistic. Especially if you're using un-ported OEM closed chamber heads, these heads are very poor. It's a shame you have flat top pistons because open chamber heads are just a better design...  

Thank you for your responce, I will send the engine out to have it line bored and have them check the balance while apart. Yes the engine has stock rods, crank, the pistons and bore are the only thing that has changed. As far as the HP rating, I got this from Edelbrock, I am using there top end package, heads, intake, carb and roller cam. I went with comp cam for the roller rockers and Edelbrock for the elect. water pump. It was there tech people who came up with the HP.
I am not that knowledgeable about what I am doing to make that kind of call, I just hope the engine stays togather when I am done......  

Well thank you for not abandoning your thread! Unfortunately that is awfully common here...

Do you have any way of accurately weighing the new and old pistons? Balancing usually runs $125-150 and if your new pistons weigh nearly the same as your old ones, you can skip this part of the machine work process. I'm just trying to make sure you don't spend any money where it doesn't need to be spent. I can't really tell you anything about the line hone other than have it checked, that needs to be mic'd.

You really didn't specify what heads you were using, so now that I know you're using Edelbrock heads kudos to you! I'm sure you can achieve these goals then as Edelbrock I'm sure is a little conservative with their horsepower ratings to prevent complaints. It sounds like you're building a great street engine and I hope it all goes smoothly for you. Feel free to ask any other questions you may have...  

I think those companies will tell you just about anything to sell you a product. I think your lucky if you make 400HP. I also have a very hard time believing rated HP on these crate engines. Take for example an LS6 rated at 450HP. These engines had mechanical cam, rectangle port heads and spun high RPM to make this kind of HP. And they had a forged crank w/ 7/16 rods to handle that RPM. As for the line hone, every performance build should start there. Every critical measurement is taken from crankshaft centerline, and it must be true. I just built a 454 with lots of goodies and I am hoping for 500HP.  

The rectangular port heads probably hurt that engine's potential...