So I'm in the process of building a 5.3 iron block, with good parts and heads, turbo with a goal of 1000-1200 wheel hp.
I've noticed that most of you guys say, if you have the choice ,go bigger cubes, and then some other guys say cubes don't matter that much when you have a turbo. My question is, yeah a 5.3 is small cubes, but the block has more cylinder wall thickness because of the small bore, compared to an iron block lq9.
So wouldn't then the 5.3 be a better option for boost cos of strength?

 

The 5.3 bore limits the size of valves you can run.... and shrouds the ones more you are running than a larger 4.0" bore. Valve size ultimately dictates how many cfm a head will flow.

If those are your power goals start with a 4.0" bore IMO. An LS2 alum block can handle 1000rwhp.... but an iron block will have stronger sleeves.

 

Small bore cathedral port heads have been pushed to 1500 HP before. The CFM they flow more dictates the N/A potential than when boost is applied. Since even stock sized valves technically flow enough air to support rather high up numbers N/A, I wouldn't sweat it too much. Too many people drastically over think these things. You won't run out of head on a 5.3, it's just not going to happen.

 

Nothing wrong with it but it will always be in the back of your mind what it would do with more cubes.

I have a iron 5.3 with TFS220's around 1000whp and plan on pushing it to 12-1300.

 

Thanks fellas, my main concern is to know that the block is strong enough, and that it is possible to make 1200 rwhp reliably with the 5.3, cheers

 

I have a built 5.3 iron block with afr 210s Shooting for 1000whp range.

 

are you running stock pistons/bore? didnt have any issues with the 2.040 valve?