Heat Tolerance for Cast Aluminum Upper Case

[YL82]

I've painted my upper crankcase with VHT Very High Temp Primer (VHT SP100). The can says to heat up to 250F for 30, then 400F for 30, then 600F (like my oven will go that damn high) for 30. This Primer is really for headers, not engine blocks & heads.

There is a caution that states not to exceed the heat tolerance of the least heat tolerant part.

What might that be for upper case aluminum?

I recall when heating up cylinder head in oven to remove valve guides that I was not to exceed 200-225F or something like that.

My top coats will be VHT SP995, which only has me heating up to 200F for an hour.

What is maximum(conventional) oven temp that I should go with my upper case?

My case is stripped down except for engine studs and the pressed bearing that the gear shifter drum fits into.

Thanks.

 

[YL82]

This thread seems to contain an answer to my question....

http://www.xs650.com/forum/showthread.php?t=1040&highlight=Valve+guide+removal

 

[jd750ace]

Not knowing the exact alloy and temper of the cases, I would not elevate them past 250 degrees. In the range of castable alloys That would be typical for this type of case, temperatures as low as 330 degrees are used for artificial age hardening.
You don't want to go up into that range and risk modifying the temper of the part in a derogatory manner. If it were me, I'd do 250 for an hour and call it good for the primer. The numbers they give are for steel and iron parts that endure higher temps than your case.
I'm not an engineer, but I know wrought and cast aluminum structural alloys pretty good.
$0.02

 

[YL82]

Thanks, jd.

I was thinking along those same lines - going no more than ~ 225-250F for an hour on the primer, then around 200F on the SP995 for an hour like the can says. As you indicated, those temp-times for the Primer couldn't possibly apply to aluminum and moreso to steel & iron parts like headers, etc.