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NorCalAnthony · 01-12-2015, 08:53 PM

Heck 123K miles is where these LS engines start breaking in so I doubt it’ll need any freshening up any time soon lol. The only reason I’m going through the trouble myself is because I knew I would be kicking myself if I didn’t clean it up and throw some go fast goodies at it before I did the swap. My project K5 runs great as it is so I don’t have a problem taking the extra time to squirrel away parts a little at a time.

When it comes time to do your own cam swap, do yourself a favor and get a custom ground cam. They cost the same as an off-the-shelf cam but will be made for your exact setup with your engine size, heads, intake, trans, stall, preferred RPM range, etc all factored in. I personally went with Martin at Tick Performance for my cam but there are many other people/places to choose from.

The rectangle port heads are what’s being used on the new high performance engines like the LS3 and L92 but require a 4.00” - 4.065” + bore because of the much larger 2.165”/1.59” valves. Besides the larger bore size the other issue you’d run in to is their different intake ports which aren’t compatible with the cathedral style so you’d have to swap over the rest of the top end with them. Also, from what I’ve read at least, they really shine above 4000 RPM but under that they actually lose power vs the cathedral ported heads due to the larger runners. They are badass heads and flow like a mo-fo but wouldn’t work with the smaller 3.78” bore of your 5.3 and wouldn’t really be worth it unless you regularly rev your engine way up there. You can read more about the cathedral vs rectangle head debate here: http://ls1tech.com/forums/generation...ort-heads.html

If you’re going for a budget cruiser then I think your 5.3 will be great just as it is. If you have the money and are looking for a max effort tire shredder then you’d most likely be better off finding an LS2 or LS3 that have much better power potential. It just depends on what your budget is and what you want your truck to be able to do. If you’d like to learn more about the performance side of these engines I’d recommend doing some reading over at LS1Tech, tons of good info on every LS based engine you can think of.

01-12-2015, 08:53 PM	#5
NorCalAnthony Registered User Join Date: Jul 2014 Location: Lincoln, CA Posts: 208	Re: ls/lm head question. Heck 123K miles is where these LS engines start breaking in so I doubt it’ll need any freshening up any time soon lol. The only reason I’m going through the trouble myself is because I knew I would be kicking myself if I didn’t clean it up and throw some go fast goodies at it before I did the swap. My project K5 runs great as it is so I don’t have a problem taking the extra time to squirrel away parts a little at a time. When it comes time to do your own cam swap, do yourself a favor and get a custom ground cam. They cost the same as an off-the-shelf cam but will be made for your exact setup with your engine size, heads, intake, trans, stall, preferred RPM range, etc all factored in. I personally went with Martin at Tick Performance for my cam but there are many other people/places to choose from. The rectangle port heads are what’s being used on the new high performance engines like the LS3 and L92 but require a 4.00” - 4.065” + bore because of the much larger 2.165”/1.59” valves. Besides the larger bore size the other issue you’d run in to is their different intake ports which aren’t compatible with the cathedral style so you’d have to swap over the rest of the top end with them. Also, from what I’ve read at least, they really shine above 4000 RPM but under that they actually lose power vs the cathedral ported heads due to the larger runners. They are badass heads and flow like a mo-fo but wouldn’t work with the smaller 3.78” bore of your 5.3 and wouldn’t really be worth it unless you regularly rev your engine way up there. You can read more about the cathedral vs rectangle head debate here: http://ls1tech.com/forums/generation...ort-heads.html If you’re going for a budget cruiser then I think your 5.3 will be great just as it is. If you have the money and are looking for a max effort tire shredder then you’d most likely be better off finding an LS2 or LS3 that have much better power potential. It just depends on what your budget is and what you want your truck to be able to do. If you’d like to learn more about the performance side of these engines I’d recommend doing some reading over at LS1Tech, tons of good info on every LS based engine you can think of.