I've read a bunch on this, and most answers are "same design but Iron" But the real question is, I know a 5.3L can be bore to the same max spec of 3.905 as an LS6, and all components, cam, crank, heads swap over...


But are there any block differences? I am most concerned about Oil galleys and passages...

The reason I ask...
I am currently rebuilding/repairing my LS6 in my road race car, turns out the block is trashed, Cylinder #8 is out of round and unable to be bored out(already at the max 3.905" bore. So I am in need of a block.

The iron block, although heavier(65-80lbs from what I've read) would give me more reliability and security.

But I am concerned about oiling in a 5.3L for a serious Road Race Application. It is not a max HP effort, only @ 380-400rwhp. But the car can/will pull 1.5-2g's at times, and oiling is my main concern.

Thoughts? Should I... 1. just find an Ls6 block replacement, or is a 5.3L up for the task? I found a full 5.3L motor for $50 delivered to my door, and having trouble even finding a decent used Ls6 block.

 

here is a map I made of my LM7 block

 

Does the LM7 have the same rear oil galley "window" that the LS6 has or is it just the 2 holes? like the older LS1?

Thanks for the pic!

 

If you are referring to the "Rear Cover Passage" on my diagram, the block has 2 holes and the oil runs through a channel that is integral to the rear cover.

 

This is what I am referring too. does the 5.3L have the top or the bottom? Thanks!

 

Best I can remember my 5.3 is like the bottom

 

I am pretty sure that the older design lm7 (up to 2003) is just like the ls1 as far as not having the bay to bay breather window that you are talking about...I think the newer 5.3s (not sure of engine code) have the ls6 style breathing capacity...

 

my 2004 LM7 is like the top photo, but I don't really see an effective difference because here is a pic of the channel in the rear cover. Oil still flows by in both designs.
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Yes I agree with the last post and if it is an older 5.3L then You can open up the passage in the rear cover very easily and quickly ,,,,,,,I did mine by hand with a 3/8" course round file in about 15 min .