heat treat head?

Can an overheated aluminum engine head be heat treated (with weights on
it to keep it flat) to bring back its temper and hardness?
Joe
Reply to
joe_d_builder
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Reply to
Tim Williams
Not sure about weighting and heat treating aluminum - it sounds like the source of more problems to me. Several years ago I had a severly warped aluminum manifold on a small V-8. One clever mechanic recommended epoxy under a new gasket instead of big $ for a new manifold. I went with his idea. He kept the car over 24 hours for a "good cure" of the epoxy (I think he used JB Weld). Success! I drove the car several thousands of miles afterwards and nary a leak
Bob Swinney
Reply to
Robert Swinney
If it's going to warp there is nothing you can do to prevent it. It's all about internal stresses in the metal. If such weight keeps it flat, it will warp upon removal of the weight.
Lane
Reply to
Lane
Besides, head bolts under tension will probably exert more force on the head in use than the weights would. And the head, in use, will see a bit of heat...
Reply to
Dave Hinz
" Besides, head bolts under tension will probably exert more force on the head in use than the weights would. And the head, in use, will see a bit of heat..."
Yeah! Bit of heat is right! What caused my manifold to warp: The thermostat came apart and locked itself in the closed position. Engine overheated; stupid driver continued to drive until just before engine seized; engine survived, heat caused aluminum intake manifold to severly warp beyond sealing range of new gasket. Epoxy to the rescue.
Bob Swinney
Reply to
Robert Swinney
Not quite enough information. Ned to know the alloy.
For example, if the head is made in 356-T6 aluminum, then it was heat treated at the factory. The T6 procedure is to heat the casting to about 1000 degrees (this is below the melting point of course) soak at that temperature for a specific time (say 6-10 hours). The elements undergo a homogenization process at that time. Then quench the casting in water very quickly (immediately upon removeal from the oven). Then the quenched casting is "aged" by placing it into an oven at a lower temperature, for example 275 degrees. When this is done the elements that are held in solution (due to the quench) will "precipitate" or come spontaneuosly form within the casting. During the "aging" process the precipitates are formed and these precipitates give rise to increased hardness and thus strength.
So by overheating you might have overaged the cylinder head meaning after careful inspection (for cracks) the entire process would need to be completed. The temps are approximate don't go by them to do a heat treat. I worked at a foundry that straightened castings after heat treat. This can be done for minor warpage. If the block was overheated the danger is for knowing that in overheating the castings have "overaged" meaning the strength is past it's maximum and could be softer (and less tensile strength) than when it left the factory.
Mark
Reply to
Mark

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