kevali

i have a01 silverado 1500 ls with 706 heads with the affected castech mark.My question is what can i replace them with?

Joe69z28

Whoa Nellie what makes you think these heads are bad . Just because they are castech does not necessarily make them bad . First have done a visual check in the areas prone to crack . Then take to a good machine shop and have checked . The bad ones were in later years most of time ! If turn out to be bad get some 862s

RB04Av

If they aren't broke, they're fine, as-is.

The place they crack, is right below the center-most 3 head bolts. You can look at the area around those bolts (take off the rockers to see down in there) and it'll look steam-cleaned, might even have visible droplets of coolant sitting there. Bottom line, they leak AF into the oil.

If you run the green stuff, ... your oil will turn into something powdery and not oily, and your main & rod bearings will dissolve quickly. You'll know.

If you're using the orange, it'll blow a YUUUUUUJJJJJE puff of smoke at startup after it's been cruising for awhile, the inside of the oil fill cap will look like it has some kind of optional body fluid all up in it, the oil will be kinda black and thick-looking, and the oil pressure will drop quickly after putting in a new filter and then come back for a few hundred miles if you change the filter.

People also say that 799/243 off of a later-model (07? up.. not completely sure the year) 5.3 are a good substitute but I've never done that so I can neither confirm nor deny.

kevali

I've done a visual check and found one port clean in the area In question,I can get my hands on a set of 5.3 heads or the whole motor.

JoeNova

Any 706/862 head. Not all of them are Castech.

The number of heads cast by Castech is astronomical. Even if 1000 706 heads have cracked, its still a VERY VERY small % of them and you shouldn't worry.

RB04Av

That's not true.

Cracked Castech heads are LEGENDARY. As far as I've been able to tell, probably a quarter of them in the 01 - 04 range at least, came from Castech; and of those, probably at least half with over 150k miles have cracked. And of course that's "old GM" so "new GM" won't do a damn thing about it.

I just replaced the 2nd set on my Av this past weekend. I should have gone with later-model ones but these were warranty, after being welded up in all the vulnerable places. But one of them cracked again in 2 spots anyway.

JoeNova

Half? So you're basically saying that every single 01-04 Castech equipped vehicle has cracked one of its two heads in its lifetime.

TOTAL bs.

RB04Av

You apparently haven't ever hung out on any truck forums. You'd evidently be amazed to actually LEARN something, and find out how common the problem REALLY is.

An estimate of 1/8 of all trucks in that era equipped with 4.8 or 5.3 having experienced this, is probably on the low side.

gagliano7

Think about how many 706 castech heads are out there on millions of trucks and suv's that don't go on forums. I never heard of the cracked head problem until i went on this site. And the one thing you get on forums more than anything are the complaints.

stockA4

I've been beating on my 02' castech headed J/Y 4.8 for over two years now with no problems. I'm sure if the were going to break they would have by now lol

kevali

I know a 5.3 will fit but are there any modifications you have to do, keep in mine I will use the 5.3 computer.

RB04Av

Will fit what?

"Beat" doesn't really seem to have anything to do with the Castech failure... it's more of just a thin place near the bolts that cracks from heat cycles or the like. Seems like somewhere around 125 - 150k miles is when they let go, if you have ones that are destined to fail.

BTW the later heads have a larger chamber. Those 5.3s have flat-top pistons whereas the earlier have dish. So they're not really a direct bolt-up option.