Anyone done a head swap on the 5.3? (799 castings, other?)

[Reprise]

I did search the forums, and found it hard to believe no one has written about doing this on the V8 - but since I didn't find anything, here goes...

Right now, my LM4 is running just fine, as far as I can tell (it has a small oil leak, but other than that, everything is fine (according to Torque Pro, at least).

Since I've got a brand new / beefed up 4L60 in the beast, I'd like to add a little more 'oomph' - nothing major - not looking to go with a blower right now. Don't want to put on a CAI; so I figure my best bet might be to put a set of 'cathedral port' LS heads on her - it's my understanding that the stock heads aren't as efficient / don't flow as well as some others.

Not looking for tons of HP, and I don't want to do a full engine swap, say with an LQ4 or LQ9 6.0L, or whatever went into the TBSS - I'd go the FI route before doing that (including routing out the hood if needed to make it all fit).

I've read that perhaps the best choice for me might be the '799' (casting #) heads - although I'm open to suggestions in that area. Thoughts? Oh - and happy holidays / Merry Xmas to all of the Nation!

PS: Back in 'the day', I put a set of 307 heads on a 305 block - so I know what I'm in for, effort-wise. Also, I've found a set of 799s locally, and would like to move on them if feasible. Seller wants $600 for them, which I think is pricey, but they've been rebuilt / polished, valves lapped, new .550 springs, etc. - ready to bolt on.

 

[northcreek]

I'm no expert on this but, 07 on 5.3's had the 243 heads and from what I read they are the most desirable.The 243 and 799 heads are pretty much the same, dismantlers claim that they often find one of each on the same factory truck engine. You might want to do some research into the 243.

 

[Mooseman]

At least with the LM4, you don't have to deal with the DoD crap.

Saying that you want to put on some "cathedral" heads, all LS engines have cathedral heads, which is describing the shape of the intake runner at the intake manifold.

I don't know about the heads but I have read that our truck intake manifolds are made to produce more torque than HP whereas the car version (i.e. Camaro) is for HP. Since you have an XL, I'd stick with making more torque than HP.

Either way, whatever you do, you may need a dyno tune to dial in the heads, especially if they change the compression if they have smaller combustion chambers. In fact, even before doing a head swap, try a mail order tune. I got one from Lime-Swap and it really woke up this beast.

I know that if and when my engine blows up, I'm gonna grab a 6.0L truck block, build it up and throw that in there. The 5.3 is a good engine but you still can't beat displacement even if it's an iron block.

 

[Reprise]

I'm no expert on this but, 07 on 5.3's had the 243 heads and from what I read they are the most desirable.The 243 and 799 heads are pretty much the same, dismantlers claim that they often find one of each on the same factory truck engine. You might want to do some research into the 243.

I wasn't aware the 243s were installed on anything except Z06(?) Vettes, and they were harder to find / pricier as a result. That's why I was concentrating on the 799s, as there's a lot more trucks than Vettes out there. Interesting to hear that the truck motors mix / matched the two castings!

At least with the LM4, you don't have to deal with the DoD crap.

Believe me, I am very thankful for that. Wasn't aware of it when I bought the vehicle, but reading what DoD owners have to deal with, bypassing / removing the system, etc. - I lucked out for sure.

Saying that you want to put on some "cathedral" heads, all LS engines have cathedral heads, which is describing the shape of the intake runner at the intake manifold.

Yep - I misspoke here - AFAIK, the LM4 *has* cathedral ports - what is an improvement on that are the 'rectangular' port heads (like the 243s / 799s) - but I don't want to raise the compression, either, after reading some more about those heads - and I'd need to compare the piston types for each motor, too - although I might have to do a cam swap in order to see the extra lift / duration those 'hot' heads are capable of. At that point, I start thinking of a motor swap, instead of swapping heads / cams.

I don't know about the heads but I have read that our truck intake manifolds are made to produce more torque than HP whereas the car version (i.e. Camaro) is for HP. Since you have an XL, I'd stick with making more torque than HP.

That's exactly what I want. I don't want to 'go fast' - I want extra / reserve power for towing. If I'm pulling 6K up a grade, taxing the engine less would be good. How I wish our platform had a 'tow mode' like the other GMTs of the era - although if I keep the trans in 3rd, I'm accomplishing the same thing.

Either way, whatever you do, you may need a dyno tune to dial in the heads, especially if they change the compression if they have smaller combustion chambers. In fact, even before doing a head swap, try a mail order tune. I got one from Lime-Swap and it really woke up this beast.

I'm embarrassed to say that I didn't think of this - it's by far the better / easier (& even cheaper) solution for someone like me - I'm not in my 20's any longer, nor do I have the free time that I used to back then. If I ever find myself in your neck of the woods, or see you at a meet, the beer is on me!

I know that if and when my engine blows up, I'm gonna grab a 6.0L truck block, build it up and throw that in there. The 5.3 is a good engine but you still can't beat displacement even if it's an iron block.

Again, we're on the same page. I'll take the added durability (& power) over ~ 80lbs of weight savings.

At some point, I know I'm going to be wanting to replace this with a Silverado - but I haven't hit the wall with this vehicle yet, capability-wise, and there's too much service life left in this one (especially w/ a brand-new rebuilt / bullet-proofed tranny in her).

Thanks to both of you for the insight / replies. Now to start doing my homework on 5.3L Lime-Swaps

 

[northcreek]

Here is the link regarding the 243 heads. As you can see the engine is definitely for a 360 application and has the 243 heads, so maybe they are not that hard to find. It's a thread from 2010 but, has some good pics.
http://ls1tech.com/forums/conversions-hybrids/1230072-finally-engine-lm4-what-hell.html