I'm starting the build-up process on a set of unposted "G" heads that will go on a near-stock 292. Had them Magnafluxed and pressure checked, but as this might be a good time to clean out the rust/scale I noticed in the coolant passages, I am tempted to fill/soak them with a commercial flush solution. But, if the scale is sealing a hidden crack, I would have to lug them back and pressure-test a second time to avoid wasting a lot of work. What do the pros normally do? Is it worth the effort to soak them? Should I fill/drain with Stop Leak afterward?



I will have to pull/change the temp sender bung. Does it need to be pressed in, or just fitted/sealed with J.B.Weld?



I milled off about .007" just to square them up initially, but may take off up to .010" more after most of the work is done. I'm thinking a clean-up cut off the intake/manifold surfaces will insure a good gasket seal, even after the block is zero decked. But, my question concerns some of the pitted sguish surfaces left outside the combustion chambers. Is it normal to mill them flat when doing a good build-up (assuming the cut does not exceed the CR/manifold seal/head thickness limits)? Will it hurt to leave any pitting?




6 VOLTS/POS. GRD. NW INDIANA

Definitely pressure test the heads after any cleaning processes that are performed.  I've had one head to come back and bite me due to corrosion in the water jackets creating a very small pin hole and was only seeping fluid back into an intake port only when pressure was on the cooling system.  If the heads check out okay with the pressure test, then I'd refrain from arbitrarily using any Stop Leak.

Before milling the heads any more, consider cc'ing the chambers to see if one head needs to be milled more than the other in order to equalize the cc's between the pair.  You may find that you'll need to mill one end of the head more than the opposite end just to equalize the cc's in an individual head.  Some rust pitting left on the decks combustion surface will not be a problem as long as the pitting itself is not on the sealing ring portion of the gasket.

Lorena, Texas (South of Waco)

The other thing that can be done is to have the heads impregnated after cleaning, before machining. In Aluminum they use sodium Silicate or an Epoxy solution that is applied while the head is under almost total vacuum in an autoclave oven. This removes all the air from the porosity and allows the solution to enter the void. Air cures whichever is used and then Ambient pressure will help force this mix into the holes when the vacuum is released. 

Frank/Rebop

Bristol, In ( by Elkhart)