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So, I finally got my engine somewhere that I can work on it this weekend. My buddy offered to let me get the short block that I was given all put together in his garage. I only made a little bit of progress today. I was really excited to find out that it is a 4.8 lol. I got the thing cleaned up with degreaser, and pulled the heads off. Its pretty clear that whoever this was did not stay up on oil changes lol. I only took a few pics but ill try to post them up here.
If the heads are the legendary Castech POSs, might be a good idea to pre-emptively swap them out for a set that's had the area above the center 3 bolt holes under the rockers welded up. Which might be why the oil looks so terrible. If it's all covered in brown slimy goop inside, as opposed to the traditional black sludge, then it has had the leak for awhile already, and putting it back together with the same cracked heads would be a major mistake.
Good stuff! Keep it rolling along. Just use a quality gasket kit (GM or Mahle or Victor Reinz - NOT Felpro) Use new GM TTY or better head bolts.
I bet the bottom end is fine. Check bearings just in case. Really, these are easy to work on and only require a couple specialty tools.
Have fun with it. Since it is a beater motor, just get it running and thrash hard!
2nd Edit: if the heads are suspect, some CL el cheapo LS heads should be fine. You should be able to find for under $100 a pair. I'll agree w/ RB04Av, be careful on Castech heads. Really just buy clean stuff.
If the heads are 706 and have a casting mark on a raised boss near one end that looks sort of like a D cell battery, then they're this kind of head, and prone to this crack. If ANY of the bolt heads or the area around one looks steam cleaned like this one, and/or you see ANY evidence of coolant ANYWHERE inside the engine, then you need heads. Preferably either NOT Castech, or Castech where that spot has been welded up in all 3 places on both heads. NOT just go to the junkyard and buy a set because they're just as likely to have, or to be about to have, the same problem, unless THEY have already been welded up.
Oh...thanks for the info guys. Now I get what you were saying. The heads that I have are the, "862s." What can yall tell me about them? I can get some pics of them tomorrow after work. I have the rockers taken out of them right now for cleaning and I am thinking I should upgrade the valve springs?
862 is pretty much the same head as 706. Doesn't have this particular problem though so that's one less thing to have to worry about.
What are your plans/goals for this motor? Being a 4.8, I'd suggest not sinking alot of money and effort into it, if it's things you can't get back out... don't mess with the short block except for a cam, don't spend gobs of money on heads, etc. I sure wouldn't mess with boring it and stuff like that.
Yes you should upgrade the valve springs. Even on a stock cam, they help. You can get decent ones for not too $$$.
Put a new oil pump pickup O-ring (make sure to use the correct thickness... there are 2) and a 2nd pickup retainer in it. If there's any ONE weakness in the design of this type of motor, that's it.
862 is pretty much the same head as 706. Doesn't have this particular problem though so that's one less thing to have to worry about.
What are your plans/goals for this motor? Being a 4.8, I'd suggest not sinking alot of money and effort into it, if it's things you can't get back out... don't mess with the short block except for a cam, don't spend gobs of money on heads, etc. I sure wouldn't mess with boring it and stuff like that.
Yes you should upgrade the valve springs. Even on a stock cam, they help. You can get decent ones for not too $$$.
Put a new oil pump pickup O-ring (make sure to use the correct thickness... there are 2) and a 2nd pickup retainer in it. If there's any ONE weakness in the design of this type of motor, that's it.
Yeah...Not planning on doing much to the engine. There are tons of these at the junkyards. I plan on boosting this thing and abusing it lol. Im more concerned on learning how to tune it before attempting any sort of tuning on an expensive engine. I have heard about this o ring thing before. Im guessing they fail? There is a popular valve spring folks use isn't there? PAC? Also, what do you think about putting rings in it that are brand new and gapped properly for a boost application? Worth it?
The O-ring doesn't so much "fail" (although sometimes it does) as, the tube isn't real secure in the pump, which if it moves, allows the O-ring to leak, in which case the pump sucks air instead of oil. There's only 1 bolt holding the tube in, stock; but there's another bolt hole on the other side of the tube, that an additional bolt & clamp can be added to. There's a bunch of those on the market.
As far as rings, that would depend on how much boost you plan to run... if it was me, I'd keep the boost down to 10 - 12 psi, and try to avoid messing with any of that. Run it til it pops.
Oh...That makes sense. I definitely do not want that going on. I do have to change the oil pan so, it will be all exposed. I have not done much as I have been so tired from working in the heat but, tomorrow night I am going to start cleaning the heads up. I appreciate the solid advice and information dude.
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Awesome day 
