Powdercoated block / filling pinholes

[cactus bastard]

I have an engine block that has been powdercoated, and I would like to keep it looking nice for as many years as possible.

The problem is that it looks like the block was not prepped well enough, and the finish is completely full of pinholes.


If I leave it like this, it will start rusting pretty quickly, and then the silver will start flaking off.

I've considered a few options and would like feedback or insight.
I could rub JB weld into the pinholes, then wipe the excess off of the exterior with acetone on a rag. That should work pretty well I think?

I could also do the same thing with some some Eastood epoxy paint w/ stainless additive that I have.
"Eastwood's 2K Detail Gray Epoxy coating is a two-component system exhibiting excellent adhesion and anti-corrosiove properties as well as superior chemical resistance and durability. The stainless provides structral integrity, impact resistance as well as abrasion resistance and produces a stainless-metallic finish with a smooth satin sheen."
This stuff would be easier to work with, but is only rated for 300'F. Most engine block paints are rated for like 500'F .

[Atilla the Fun]

IDK if your exhaust manifold or header gets anywhere near the block, but otherwise the outside of the block should never exceed 220 degrees F.

[cactus bastard]

I didn't really think the 300 rating would be a deal breaker either, whatever I do use to fill the pinholes will be performing the role of a sealant more than that of an actual coating. It will be protected from abrasions or impact by the powdercoat.

[The Dark Side of Will]

Did you pay for the surface prep or the coating job?

[cactus bastard]

No, bought an assembled short block from somebody else.
Also, I'm not actually willing to strip down and re-coat.

[The Dark Side of Will]

Is that an S10 2.5 block, SD or something else?

[cactus bastard]

2.3L quad 4, will go in my 84

[The Dark Side of Will]

Get another block and have the powder coating redone. Q4 blocks can be had dirt cheap.

[Atilla the Fun]

You can get complete Q4s around here for $150, any day of any week.

[Series8217]

Temperature rating is definitely not a concern for painting an iron engine block. I have had my block painted with plain ol' Rustoleum from the hardware store, and it still isn't coming off after over 30,000 miles.

As to your main question, I agree with the others... if you're thinking about stripping it, just get another Q4 block..

[cactus bastard]

I bought this assembled short block because all the machining was complete, including having the cylinders honed with a deck plate (and because of the forged pistons and rods, and balanced rotating assembly). I'm not about to tear it down and get an other block completely machined, nor am I interested in completely stripping it and having it professionally coated.

If I can keep the existing finish on there as long as possible, that's all I'm after.

[Emc209i]

If I can keep the existing finish on there as long as possible, that's all I'm after.

I'd roll with an heat resistant clear coat then. I've used Eastwood's engine clear before and it sucked, had better success with the more expensive clears to be had at the local automotive shops.

[cactus bastard]

I wonder how well they would adhere to the powdercoat though? And should I still fill the pinholes with something before the clearcoat?

[Emc209i]

Should adhere just fine. You can paint over powder, but you can't powder over paint, that's generally the rule. I'd recommend a quick wipe down with mineral spirits on a cloth first - get any fingerprints, oils, contaminants off the surface. Personally I think trying to fill the pinholes with JB weld is a bad idea. First thing that comes to mind it the color and texture; it's going to be darker than your coat of silver and plastic looking in contrast to the casting texture. Secondly, if you clear over the top of JB weld, the clear may not cling to the JB. JB weld turns to soft toothpaste when it gets hot - high temperature formula or not; I don't see clear coat clinging to something that changes state from a solid to a gel with the heat cycles of the engine.

What I think is good idea: wipe the block down with mineral spirits and then apply two or three layers of clear, allowing each layer to dry before adding the next. The objective will be to seal off the orange peel dimples so that oxygen can't get to the block surface and begin the oxidation process behind the powder coat.

[Series8217]

Can you sand powdercoat to improve adhesion? You shouldn't have any problems painting over it if you can. A clearcoat would make the finish shiny again once sprayed over the sanded powdercoat.

[Emc209i]

Sure. In my experience a clean powder coat surface is plenty sticky for paint. Just depends on how thorough you want to be, and how dirty the block is -any oils on the surface are going to cause problems. From my past readings I've collected that 1000-1500 grit should be used to scuff the surface. I've used 1000 grit paper once before; I couldn't really observe any difference from the non sanded parts. Albeit the parts were new and not subjected to heat in that particular case.