Castech heads ?

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Woodblocker55

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Ok I was reading everyone's blaming the 706 castech heads .. there saying they go out at 80,000 miles mine has 174,000 mile no coolant leaks .
Is there some abuse going on or some defects . Back in the 60-70s this was a problem because cast iron and aluminum had different expansion rates.
It's sounding like same issue . Or is it the coolant eating up headgaskets ?

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Woodblocker55

Woodblocker55

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I was searching more 706 heads were made by different venders so you need to pull valve covers to see if there made by castech . And what happened the aluminum was to porous ..meaning to many impurities in the aluminum casting. And it seems this problem shows up with a lot of aftermarket cams and stuff. Anytime you aftermarket anything you're rolling the dice. Gm spends thousands on reseach . Aftermarket has there place . After gm stops making the part and there no parts left in junkyard.

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iamdub

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Abuse could certainly be a factor in some failures, but the known issue is due to a defective casting. They usually crack right around the head bolt recess/oil drain area, and usually the middle ones. The different expansion rates and gasket issues have long been resolved through technological advancements in engineering. Head bolt torque amount and sequence is more important than ever before. This is one reason why they use torque to yield bolts rather than ft. lbs.
 

Larryjb

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Just so you know, I had a non-Castech crack on me. It's probably not common, but it can still happen.
 
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Woodblocker55

Woodblocker55

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I need to put in new valve cover gaskets in .. so I will find out then I guess .. it's a pretty strong motor yet . Only issue I found was 2 missing exhaust manifold bolts . Witch make ticking sound till engines hot . Checked gas mileage 18.5 mpg with lead foot at wheel and 21 mpg at 60 mph . Witch is way better then thought I would get.

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iamdub

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I need to put in new valve cover gaskets in .. so I will find out then I guess .. it's a pretty strong motor yet . Only issue I found was 2 missing exhaust manifold bolts . Witch make ticking sound till engines hot . Checked gas mileage 18.5 mpg with lead foot at wheel and 21 mpg at 60 mph . Witch is way better then thought I would get.

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You'll need to clean the area well and get a mirror or borescope, good lighting and patience to look for the Castech symbol with the rocker support in place. Since Larry mentioned it, yes, any head can crack. The Castech 706s are much more prone to it due to the defective castings. On the other hand, there are plenty of Castechs that are fine. It's definitely worth closely inspecting when you pop the covers off. I don't know about any particular mileage where they fail, but my brother bought his truck with 171K and we're sure his was cracked before he bought it because he had to add coolant every 3-4 weeks since buying it. Once I got inside the engine at 181K, it was obvious it had been cracked for quite some time.

Just see what you have when you have the covers off and keep it in mind. If you ever need to start adding coolant and it doesn't appear to be an external leak, then you'll already be a step ahead.
 

Tonyrodz

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You'll need to clean the area well and get a mirror or borescope, good lighting and patience to look for the Castech symbol with the rocker support in place. Since Larry mentioned it, yes, any head can crack. The Castech 706s are much more prone to it due to the defective castings. On the other hand, there are plenty of Castechs that are fine. It's definitely worth closely inspecting when you pop the covers off. I don't know about any particular mileage where they fail, but my brother bought his truck with 171K and we're sure his was cracked before he bought it because he had to add coolant every 3-4 weeks since buying it. Once I got inside the engine at 181K, it was obvious it had been cracked for quite some time.

Just see what you have when you have the covers off and keep it in mind. If you ever need to start adding coolant and it doesn't appear to be an external leak, then you'll already be a step ahead.
Do you have any internal pics of your bro's motor damage from all the coolant? I don't remember if you already posted it. My old 4.8--862's iirc--would lose coolant, which I'd have to refill also every few months.
 

Larryjb

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The crack in mine was very obvious with the valve cover removed. A coolant leak will clean the local area quite a bit.

To prove the leak, I cleaned the area as suggested, wiped it with a tiny bit of acetone to dry the area, and took a close up picture of the area. Then I pressurized the cooling system, waited, and took another picture. This was actually very useful to me because I took my head in to get rebuilt, and to replace the cracked head. When the shop pressure tested both heads, both of them passed the test! Apparently, this only leaked when torqued down to the block. The machine shop agreed from my pictures that it was cracked and replaced it.
 

Tonyrodz

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The crack in mine was very obvious with the valve cover removed. A coolant leak will clean the local area quite a bit.

To prove the leak, I cleaned the area as suggested, wiped it with a tiny bit of acetone to dry the area, and took a close up picture of the area. Then I pressurized the cooling system, waited, and took another picture. This was actually very useful to me because I took my head in to get rebuilt, and to replace the cracked head. When the shop pressure tested both heads, both of them passed the test! Apparently, this only leaked when torqued down to the block. The machine shop agreed from my pictures that it was cracked and replaced it.
Good thing you noticed it before bringing it to the shop! Can you imagine--putting the cracked head back on! You'd be like wtf!
 

SnowDrifter

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Abuse could certainly be a factor in some failures, but the known issue is due to a defective casting. They usually crack right around the head bolt recess/oil drain area, and usually the middle ones. The different expansion rates and gasket issues have long been resolved through technological advancements in engineering. Head bolt torque amount and sequence is more important than ever before. This is one reason why they use torque to yield bolts rather than ft. lbs.
And let's not forget multi layer head gaskets that are quite literally designed to slide around. It's goofy but it works!
 
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