Hello,
I think I found a new home here, I love fixing things that are not broken!
Questions on the Castech #706 casting coolant leak problem?
Does the leak start only after the engine has been once over heated or do they just start leaking?
Is the “Genuine GM (122378255) Fluid cooling system seal tablets” a good preventative stop leak measure on a non-leaking #706 heads?
Should I keep my #706 non-leaking as of now heads or buy used #862 heads and overhaul them?
At lest I could take my time getting the head work done having an extra set.
The reason I am asking is that my next mod is to do some head porting [valve seat to port blending and better the only-two angle stock seat angles] and checking the exhaust port to header size. Maybe increase the combustion ratio, and check the valve train geometry.
I can buy a pair of #862 casting heads at the local salvage yard for $175, 2005 heads from a 5.3 pickup. They are still on the block and will take a look before buying them.

I bought the 2002 truck new and now have 80,000 miles on it. I know that the #706 heads are the smoother SPM castings and flow better pre-porting than the sand cast #862s.
Thanks in advance for your input.

 

Well, my 2002 Tahoe is on 706s, has been for 188k. Its made 477whp, its currently ~500 we think based on injector load and upgrades

Its been overheated 3-4x while dealing with electric fan things, or the OE clutch fan failing, or just being mean to it (bad me)

Its had its coolant flushed twice in 8yrs with Dex (radiator/cam swap in 2014, cam swap in 2017)
Bout to be a 3rd time because the stupid aluminum rad is leaking

Stock heads/bolts/gaskets: no cracks, no consumption, no leaks (net even oil, now )

The ginger tablets are generally for aluminum block motors. They wont really be of benefit to you on the cast iron motor. They help coolant from weeping out the block.

 

Thanks, that is good information on the "ginger tablets."
And answering the "Over-heating question"

 

I Never had an issue on any of my trucks equipped with 706 Heads !
Just sent a set out to get the ported. They checked out fine when they pressure tested them at 40 PSI

If you plan on porting, Wouldn't hurt to pick up a spare set to work on.

 

OK Thanks, I am planning on doing the porting myself, so I should pick up an extra set so I will have a back up if I screw the first ones up!
Or when I mess them up. I hope I don't ruin them.
I bought two "David Vizards" books and having been lessening to You Tube videos on porting as I work. Makes the work day go faster and
it looks like fun. Just have to find a machine shop to do a multi-angle seat job. When I worked in a Toyota dealership we used the Neway cutters
as the new hard valve seats were just coming out. Ya, I am that old.

 

Porting in any capacity is not a simple task. I would recommend getting a set to try your work on first.
There is lots of reference material out there.