Actually, stock compression ratio is 9.5:1. And I doubt you'll be able to go .030 overbore. Stock bore is 3.78", and the largest overbore that most go to is 3.907" IIRC. Basically, you'd have "an iron LS1" at that point, 5.7 liters.

 

Just throw in some forged slugs and crank the boost an extra pound or two. No need for boring imo, unless there is damage.

 

If you bore .030" over, the compression ratio will go up, not down. And .030" overbore would be no sweat. I bored mine .125"... there is a lot of meat there. Find some oversize forged pistons first, then take the block to the machine shop along with the pistons. That way the bore can be sized pefectly to the pistons instead of taking a shot in the dark.

 

^^^Drunk post... I suck at math when I'm drinking beer!

^^^What swift said.

 

As a general rule of thumb does everyone here replace the Main, Rod, and Cam bearings even if all of the bearings check out okay? Engine had 75k original miles... I know on a standard motor people do this but on a turbo motor it would be better insurance to just replace correct?

 

Yes, replace them all, they're cheap.

 

Just my .02, but you should make a decision on what to do with your build and possibly take a little bit of a different direction. If you are looking at putting any forged parts in that engine, your going to have to do a complete rebuild and you will want both pistons and rods. You need to just sell it and pick up a 6.0, you can punch it out .030 and have a 370 that will make serious power. Both sizes will have similar priced parts, there is just no reason to spend that kind of money and not chase the power differential with the minimal additional costs. Just to clarify the power differential, you could push a forged 370 to 750whp and beyond on the stock crank without issue.

That being said, I think a set of ported 5.3 heads with studs and ls9 gaskets would get you to 550whp with the right cam and tune at around 10lbs. That is a ton of power, probably more than you would need unless you are trying to break 10's or something. With those studs and gaskets, you could probably push it to 600 without issues if you have a good tuner. You might need a 90mm intake and throttle body also. Would still be a killer street setup for much less time and expense.

 

Would a set of 243 heads i have off a 6.0 work ok with a turbo set up or just the 317's that were mentioned