Originally Posted by SynergyV8

Indeed.

Not solely because it has more average torque, but specifically the smaller 3.898-3.905" bore will typically have slightly better thermo efficiencies which promote a more complete and efficient burn. That is why GM originally designed the first LS1 with a small bore, as GM was worried a large bore like the old school 350 would not pass emissions which were predicted to tighten up after year 2000. The larger the bore, the more difficult it becomes to pass emissions requirements.

Think of it this way: Pour two lines of equal amounts of gas out on the ground. One 3 feet long, one 4 feet long. Light them at the same time and you'll find that the flame hits the end of the 3 foot path quicker than the 4 foot path. Gasoline does not "explode" in the cylinder, it actually has a measurable burn time. Since an engine has a limited amount of time to burn the fuel, it becomes more efficient if the flame does not have to travel as far a distance.

This is why the 383 is my favorite DD engine when heavy SUV's are concerned, like my wife's. (No my I'm not saying my wife is heavy ) The 383 has the small, efficient LS1 bore with the torque and displacement you'd come to expect from a big cube motor. Whether or not the 383 will be more efficient than the 370, I will find out shortly. I believe it can and will. I see the extra displacement of the 383 over the 370 being negated by it's smaller, more efficient burn potential while the extra average torque will bring tps % down during errands and daily driving, hopefully requiring less fuel.

Originally Posted by old motorhead

Going the cheap route on the foundation of your build isn't so wise.

Originally Posted by SynergyV8

ALL 4.8L/5.3L blocks have the potential to be machined further than LS1 bore specs to 3.905", but sometimes you will find through sonic testing that certain individual bores cannot be bored past 3.898" because of the casting tolerances at the factory. If 6 of the 8 bores can go to 3.905" but 2 cannot, they must all then be the same. From my experiences with boring 5.3L blocks over, there seems to be a common trend with cylinders #2 and #6 being thinner than the others. Why? I don't know; but that doesn't matter to me. A 3.905" bore is not going to make any noticeable power increase over a standard 3.898" bore that is worth putting the cylinder wall strength at jeopardy by going that extra James Bond .007".

There is nothing wrong with a 5.3L block bored .118" over as far as strength goes. Yes, the 5.3L block was stronger left alone, but have you seen a bare 6.0L block? There's even less material! I'd bet top dollar the iron block is still stronger than any aluminum LS block that comes from the factory, except for the LSX and C5R block.

Originally Posted by SynergyV8

I agree 100%. I think what you're hung up on is doubting how strong a bored over 5.3L block really is. Using an iron 5.7L block is not one of those "cheap routes"...in fact, it's more expensive than a 6.0L block due to the all the machine work needed to get there.

Originally Posted by cmiller

how often do you see this? im in the process of building a 383 and i have already ordered the rotating assembly and im pretty sure they are for 3.905 bore

Originally Posted by old motorhead

You're right....not convinced how stong these big bored 5.3's are. If you had your choice of boring a 5.3 to standard LS1 specs vs. spending an extra, say $750, and getting an LQ4/9 block and boring it .030 over.....which way would you go? My contention is that you get more cubes (that's good isn't it?) and a stronger foundation with the 6.0.