The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by rustymetal, Jun 12, 2014.
hi got a new set of aluminum heads for a 21 stud flathead wondering would power coating warp them ?
It probably won't but why would you want to powder coat cylinder heads?
I'm not sure I know what power coating is
Can you actually increase power by power coating a pair of cylinder heads ?
i would bolt them together and torque them all the same just to be safe.
Sure, it makes the combustion chambers smaller, and that raises the comresstion (sic).
That is a good question though, they back powder coat @ 400 degrees don't they? I wouldn't think that it would warp them but even if it did you should be able to have them faced. There is always paint, I am pretty sure that painting them wouldn't warp them.
Didn't they used to powder coat WWII planes?
Supposedly, there is a low temp powder coating process but we have never been able to find a local coater who knows anything about it. We have searched because my Son wants to have the installed cage in his Mustang coated but the regular 400 degree process might warp the body. The guy we use said he does cages without problems by watching the temps and stopping before it gets really hot for too long, but we aren't going to take that chance.
You might call some coaters in your area and inquire though.
It's kind of surprising how many guys call powder coating "power coating". I wonder how that happens?
And I doubt any coating would withstand combustion temps.
I've done intakes without warping them. Maybe if you had a spare block to torque the heads to then powder coat them to be on the safe side
Don't worry about warping.
Worry about chips when you bolt them on.
I'm not aware of a 'low temp' powder coat, but you can use lower temps to cure it. The downside is the powder doesn't bond as well to the metal, and you probably won't get as nice a gloss finish. Powder uses a 400-450 degree 'flow out' heat, once it's 'flowed' the heat is dropped to about 350 for cure. You can cure as low as about 325 degrees (skipping the flow out heat) but the cure time is longer and careful monitoring of the finish is needed. This is usually used on items like springs where the higher heat will damage the temper of the metal.
I've coated sheetmetal parts at 'standard' cure heats with no warping issues, but the cure heat will damage any fillers/sealers and cause the lead in factory leaded seams to 'run', so figure on doing any bodywork after coating. I have seen cast aluminum engine parts coated (heads, blocks, etc) with no issues, but frankly paint is a better choice IMO.
People have gotten the idea that powder is a 'ultimate' coating, but it does have it's drawbacks. It doesn't like high heat, surface scratches easily, and can't be repaired like paint can.
Uneven heating/cooling is what causes warping! If you hang a head in an oven and heat it to 400 degrees, it will see that heat on all sides so there won't be any warping. (unless you take it out of the oven hot and lay it on a block of ice)
On a more serious note, some grades of aluminum will lose their strength and stiffness after the heat of the powder coating process which will anneal it and leave it in a softened condition.
Blue One, that is true with some wrought aluminum, these would be cast. Wheels are done all the time, just sayin'!
Better quit talking about it. It's not traditional and the hamb police will close your thread down. Hahaha
Alum does not take powder coat well in my experience w a piece subjected to vibrations or stress. Just my personal experience.
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Check this guy out: He powder coated his whole roadster including the Lincoln
V- 12 in it http://www.jalopyjournal.com/forum/members/frenchy-dehoux.13420/
400 wont hurt them. powder sticks to aluminum just fine. if you have a good powder guy they will do a good masking job.
And contrary to what people think, repairing a powdercoat job is easy, put it in the oven, let it wet out, apply powder and recure. I do it all the time
I did my aluminum valve covers with no problem...
Its not whether the aluminum is wrought, cast, or extruded that matters. What matters is whether its a heat treatable alloy or not. Cast wheels are most always 356-T6 which is a heat treatable alloy. Heating 356-T6 to the normal curing temperatures for steel, even for a few minutes, will reduce its strengh by half. That's why there are low curing temp powders for aluminum. Any temperature above 350*F will affect the strength of heat treated aluminum. The strength reduction is permanent and does not recover as the part is cooled.
That said, I doubt the heads are cast from a heat treatable aluminum if they're old. Newer ones might be, but the only way to know is to ask the manufacturer.
Are you referring to the exterior surface of the heads? HRP
That is not true at all. There are actually several different types of coatings that can be applied to pistons.
Like others I have done aluminum intakes, valve covers ect. no problem
I do Powder coating all the time, mostly on car parts... I have never personally powder coat heads But I have a powder that is ceramic based and can withstand 800+ before messing up the finish... and typical powder will withstand 500 for about an hour before being comprimised, but the high temp , it is not glossy. I do headers in it alot...
Intakes are easy... I would be willing to donate some time to see how powdercoating some heads would work... sorry for the spelling... its dark here. haha
But theres no way I would do any surfaces inside the heads.
There's a powdercoating that will withstand combustion temperature?
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True, but coating thickness can prove to be a problem in some cases, causing fitment issues. I use this method where extra-thick coating is wanted (like battery trays), but it's not practical for assembled parts...
Hope you know NOT to powdercoat the gasket surface side
What about like a Jethot coating? ceramic aerospace coating? I don't think I'd do the machined surfaces since it might effect head sealing, combustion issues.
Temps inside the chambers are thousands of degrees. The coatings they put on piston skirts aren't powder coatings.
No one said they were. Jet-hot coating CAN withstand actually 1300 degrees at it's minimum which is well above what engine temps will ever get to. The coatings on piston skirts from what I understand are aTeflon propriety coating.
I have had some parts warp during powder coating. The prior suggestion about bolting them together might be pretty good.
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