I had my valve covers powder coated in two different colors by a quality outfit about 3 years ago. I noticed yesterday that they both had bubbles near the center above the Edelbrock logo. Its worse in the center(above crossover) and tapers off going outward in both directions and is only along the top edge. Passenger side appears to be worse. After asking questions about my engine, powder coater said that since I have my intake manifold crossovers blocked, excessive heat is whats causing the problem. Powder coating is cooked at 400 degrees and they feel that the heads are reaching temps above that just enough to effect the coating. Engine water temp stays around 180-190. I have no reason to doubt them, but I'm wondering if anyone else has had this happen to them ?
p.s. I have crossover blocked due to vapor lock issues with my Shaker and felt it would help. It appears to have helped but not 100% positive due to other changes made at same time.
looks to me that the powder coating was applied, or prepped, improperly, in some way.
https://vandacoatings.co.uk/blog/why-does-powder-coating-flake-bubble-chip-or-crack/
I can't see the valve covers reaching 400 degrees. Around the exhaust ports on the cylinder head ok , but not the valve covers.
Quote from: Brads70 on January 05, 2018, 01:53:55 PM
I can't see the valve covers reaching 400 degrees. Around the exhaust ports on the cylinder head ok , but not the valve covers.
Yep I agree! I suspect that it was not prepped properly . . . As cudabob stated above.
Generally with the crossover blocked the heat cannot get up to the covers , with the crossover open there is a lot more heat moving through the head .
I agree with CP: I don't think the temps would raise with the crossover blocked above what they were with it unblocked.
While everything you guys are saying makes perfect sense, there's one thing that the powder coater pointed out that can't be ignored. Why is it worse directly above the crossover on both covers ? Its worse in the middle at the high point of the covers and tapers out from there, down to nothing within about 4in forward and back of the center. Thats a hellva coincidence. Like you guys, I can't see the covers getting that hot and I bought an heat sensing gun so I can get an idea of what kind of heat there is. I'm also going to pull the covers off in a day or so and look inside of them.
Cast aluminum is porous, holds lots of stuff, (oil ) It's coming out. :alan2cents:
could always pop one and see what's underneath
No denying that it would be hotter in the center of the head where the HR passage is and heat rises. I'm sure the center of the head is hotter than it is to the sides it's just I don't think it would be any hotter than in an application where the heat riser ports would be open.
looking underneath the cover, it would show, by discoloration, if the center was getting up near 400 degrees.
I need to make something VERY clear. I'm intentionally leaving out the name of the company that did it. They do very good work and I feel that what has happen to mine is a fluke. No one is 100% sure about the cause so far. They have already offered a shipping label and will redo the powder coating for free. At this point only trying to figure out wtf happen and whether its worth the gamble of redoing these covers because of possible issue with the aluminum itself or getting new ones done.
I'm guessing it's do to porosity in the aluminum holding oil or contaminants. A shop that does a lot of tig welding told me he has the hardest times welding aluminum when it has been oily before. He says it's almost impossible to get it clean enough. If these are used valve covers it will probably do it again. When they bake these it might be releasing gases but not showing it's ugly problems till later. I have had good luck painting that type of valve cover. So that could be a option. :alan2cents:
Here's pics of the bottoms. I suspect that since these were old valve covers the aluminum wasn't very good quality and allowed saturation after the powder coating was done.
Even though they probably look great when you got them back. I suspect that 400 degree bake is effecting the issue. The porosity is possibly releasing gases that eventually lead to the bubbles. IMO
I bet if you had a brand new set they wouldn't do it. I recommend painting them and bypass the big bake temp.
I agree that it's probably not the powdercoaters fault.
It has to be the powder coaters responsibility. If he can't powder coat
aluminum, then he should say that up front!
How about baking out the impurities in the aluminum, before
putting on the powder coat??? Duh!
Maybe that would work. I don't know. :notsure:
Quote from: cudabob496 on January 08, 2018, 03:25:24 PM
It has to be the powder coaters responsibility. If he can't powder coat
aluminum, then he should say that up front!
How about baking out the impurities in the aluminum, before
putting on the powder coat??? Duh!
Not as easy as it sounds. Old used casting = porous , impurities and oil saturation. Cant bake out all impurities.
I would simply paint old casting or buy new and powder-coat inside and out. (if powder-coating is that important). I wouldn't blame the company.
They were "outgassed" before anything got done for 3 1/2 hours which is basically cooking them longer and at a higher temp than is used for the coating. But apparently that wasn't long enough. :(
How much money/time do you want to spend ? :notsure:
Update...
I'll try to play nice and not tell who the powder coater is because I've been around long enough to know that sheet happens. They have now seen pics of the outside of covers with bubbles and the interiors with no sign of anything out of the ordinary(which she admits). Even after seeing that the temps of the effected area that were taken with an infrared temp gun shows 200degree range, they are still convinced that my Valve cover problems are because the crossover is blocked and creating heat in excess of 400 degrees despite the additional fact that the wiring harness from the alternator and plug wire also show no sign of heat damage. In all fairness, during my last discussion I asked if they would treat me right if I sent new ones to them, she did say yes. However, I'm tired of screwing with it and got some covers that I like as they are. End of Story.
Hmm: Well. you're doing the right thing. Sometimes it isn't worth going crazy trying to make something work when a different direction can be taken.
He chose the path of peace
Quote from: cudabob496 on January 12, 2018, 12:14:08 AM
He chose the path of peace
Or the path of least resistance!
Quote from: JS29 on January 12, 2018, 06:00:26 AM
Quote from: cudabob496 on January 12, 2018, 12:14:08 AM
He chose the path of peace
Or the path of least resistance!
I tend to do the same thing.
I'm in business fixing wrecks. Everything in the world fights you along the way and perfection is always easy to ask for. Just because something is not perfect doesn't mean that a experienced person didn't do their best. Sounds like the company offered to redo them so what else can a reasonable person expect?
In this situation I really believe the oil soaked aluminum is the culprit.
Yes: I think this is one of those deals that really no one is wrong. If I was the Powdercoater though, I would keep this in mind in the future if a similar job came up.
Quote from: RUNCHARGER on January 12, 2018, 07:46:50 PM
Yes: I think this is one of those deals that really no one is wrong. If I was the Powdercoater though, I would keep this in mind in the future if a similar job came up.
"In all the years of doing this, this is the very first time this has happen. So, its has to be because you have your crossover blocked. "
Quote from: Racer57 on January 12, 2018, 08:03:44 PM
Quote from: RUNCHARGER on January 12, 2018, 07:46:50 PM
Yes: I think this is one of those deals that really no one is wrong. If I was the Powdercoater though, I would keep this in mind in the future if a similar job came up.
"In all the years of doing this, this is the very first time this has happen. So, its has to be because you have your crossover blocked. "
Just curious.... In your communication with ths company ... you did say, She would powder-coat new covers ? ::)
Quote from: GY3R/T on January 12, 2018, 08:51:59 PM
Quote from: Racer57 on January 12, 2018, 08:03:44 PM
Quote from: RUNCHARGER on January 12, 2018, 07:46:50 PM
Yes: I think this is one of those deals that really no one is wrong. If I was the Powdercoater though, I would keep this in mind in the future if a similar job came up.
"In all the years of doing this, this is the very first time this has happen. So, its has to be because you have your crossover blocked. "
Just curious.... In your communication with ths company ... you did say, She would powder-coat new covers ? ::)
Misunderstanding somewhere. They think that I would have the same bubbling due to temps over 400 degrees no matter what I send them because they have done everything properly on their end.
They're wrong on that I believe. There is extra heat there alright that is outgassing the oil but I don't think it would happen with unused covers that didn't have oil embedded in them. JMHO.