LQ4 head questions

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iamdub

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So the 799 heads would be a direct bolt On? No swapping the pushrods or valve springs etc?

Direct bolt-on. You'd only have to mess with the springs and/or push rods if you changed the cam or had the heads decked. Keeping it all factory, it's a direct swap. Don't be expecting a huge power increase. You'll mainly feel a little bump in TQ in the low- and mid-range. If you wanna splurge, you can have them milled and ported a little, but then you're really close to entry-level CNC head price range. This sort of swap is more of a "found a deal on some 243/799s and my 317s were already off" kinda deal.
 

iamdub

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From the research I have done so far, the 6.0 didn't use castech heads, so I'm hoping that the heads and block are fine, it was just a gasket failure.. But I will know more once I pull the valve covers off..

The Castech failure seemed to be exclusive to the 706 heads that came on the Gen3 5.3, and the cracks formed in fairly particular areas. The point of my story was that a small coolant leak, regardless of where it originates, may not make a milkshake in your oil, but could still be slowly gunking up your internals. Just so you're not surprised when you open it up.
 
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Lowcountryfire

Lowcountryfire

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So I pulled the plugs after work.... cylinder 2 was the only one with coolant in it... so confirmed blown head gasket...

To add insult to injury, the water heater went out on the house, so that takes any hopes of upgrading heads out of the question right now, so I'll be replacing the gasket and keeping the stock 317 heads...

Now ever since I have owned this truck, I've never let it overheat, I know these heads are aluminum, but would I be safe in replacing the gaskets only without having the heads decked, or is decking them a must??
 

iamdub

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So I pulled the plugs after work.... cylinder 2 was the only one with coolant in it... so confirmed blown head gasket...

To add insult to injury, the water heater went out on the house, so that takes any hopes of upgrading heads out of the question right now, so I'll be replacing the gasket and keeping the stock 317 heads...

Now ever since I have owned this truck, I've never let it overheat, I know these heads are aluminum, but would I be safe in replacing the gaskets only without having the heads decked, or is decking them a must??

You probably don't need them decked, but you really should have them checked at a machine shop. That RH head could've warped or even cracked so the root failure may not be the gasket. You may have never overheated it, but it could be a flawed casting that took a while to fail. If the shop is checking them, they may as well put a cleaning pass on the decks. It's a great time to replace the valve seals and at least lap in the valves if not an actual 3- or 5-angle valve job. Be sure the shop has the right equipment for the surfacing. GM MLS gaskets need an RA finish of 20-30, which almost looks like a foggy mirror. Fel-Pro's MLS gaskets are good up to an RA of 50-60. I had a machine shop try to put my Z06 243s on their belt sander. That convo went no further!
 

Larryjb

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The Castech failure seemed to be exclusive to the 706 heads that came on the Gen3 5.3, and the cracks formed in fairly particular areas. The point of my story was that a small coolant leak, regardless of where it originates, may not make a milkshake in your oil, but could still be slowly gunking up your internals. Just so you're not surprised when you open it up.

My head was NOT a Castech, but it failed. Even though I was able to prove it was cracked by pressurizing the cooling system and seeing the coolant seep through the head, when the machine shop tested the head they saw no evidence of the leak. It seems that the torqueing down of the head opened up the crack just enough to start leaking.

I know your leak is in a different location, but if you cannot find evidence of the head gasket failing, have the head tested. If you can, remove the valve covers and pressurize the cooling system then look into the intake port for the #2 cylinder (the one you say is leaking) and look for evidence of coolant. You may need a boroscope. Chris is right that the Felpro gaskets can seal larger surface imperfections than the OEM gasket.

When you dig into this, you may find my experiences helpful. Or not, but here it is anyway:
https://www.tahoeyukonforum.com/threads/5-3l-head-removal-2002-tahoe.108649/
 
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Lowcountryfire

Lowcountryfire

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That checklist is awesome!

I talked to a few buddies of mine that have some more LS knowledge than I do, and Operation Head Gasket has been scheduled to take place next saturday.. I got a felpro gasket and bolts, and between my friends they have spare intake gaskets, exhaust manifold gaskets etc.

If I can't find any signs of gasket failure, I'm definantly taking them to the machine shop, problem is there is only 1 in my area, and he's usually backed up a week or two, and this is my dd, so hopefully itbwas just gasket failure..

Hopefully I make a bonus this month so I can start building an engine for this thing... 500 na hp sounds like a good goal....
 

Larryjb

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That checklist is awesome!

...and he's usually backed up a week or two, and this is my dd, so hopefully itbwas just gasket failure...

Consider yourself lucky. The machine shop I used was backed up a month!

Good luck!
 

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