Great site am glad I stumbled onto it.

I recently discovered my 04 Silverado with the 5.3 has been losing coolant from either a head gasket (doubtful) or the dreaded castech heads that cracked. My question is this, a friend has a set of heads off an 02 Silverado 4.8 with less than 10 k on them and will sell them for a better price than reman's. My question is will these bolt right up? Valve size the same? Any differences at all?

 

I can't remember if they used the same casting numbers for 2002 and 2004, but they will work. They do have the same valve sizes.
If you want to verify that the head is cracked you can take the valve covers off and take a look at the head bolts, typically one of the bolts will look clean and a small area around the bolt will look clean, everything else should look brown and oily.
I had the same thing happen on my 03 Silverado 3 years ago.

 

Yep sure enough I tore down the passenger side and it is cracked right around the head bolt. The bad cast heads by Castec were 706, the good ones are 852. I see a boat load of the 706 cylinder heads being sold on Ebay as remanufactured heads but how do they fix cracking? I think I will steer clear of all 706 heads and try and find the 852's would hate to have to tear into this motor again in 80-100k miles

 

I put a set of reman heads on the wife's 04 Sierra to replaced the cracked originals. They were TIG welded around the weak areas. These have been on the truck for almost 50,000 miles and no problems yet.

 

you can find used 5.3 heads for $50 or less most places.