prepping a block for paint

so i thought i cleaned my block well, serious scrubbing with hot soapy water and a good rinse, but it seems there is still a film of oil on it in some places.

what is the best way to really clean it off to prep it for paint? can i just wipe it down well with a rag and lacquer thinner?

oh, and it's already a long block and mostly taped off. i figured this out as i realized the tape was not sticking well at all to the block.

1,1,1 Trichloroethane would probably do it. That is what used to be in brake cleaners. If you are still able to get the non-flammable kind I'd try that first. You have to saturate the surface so the oil dissolves in the cleaner and then evaporates.

My friend uses lacquer thinner for this.

R.

Trichlor is nasty stuff. Carcinogen and ozone depleting. I use brake clean on rag. Then blow off lint that the rough surface catches. Then wipe again with wax and grease remover. Blow off yet again. I also use an industrial primer. I got a couple of quarts from a supplier. It was red oxide and I brushed it on. I think it was a Rustoleum product. Seemed to work great. Did this on last two engines I built. The 440 was done 10 years ago. Although the engine is now disassembled, it still looks pretty good. My hemi was painted last year so no run time on it yet.

I would get a gallon of wax and grease remover & with a clean paint brush and scrub brush go over it vigorously repeatedly with enough of it to where it is dripping a big mess under the eng. then finish up with several cans of brake kleen, drowning it & it'll get into the pores/nooks and crannies. I would not use any rags. They were referring to painting a flat surface but the paint guys at Sears once told me that you use solvent (of an appropriate type of course) to raise the oils/debris then you must wipe it off when wet otherwise if it dries the oil just goes back down to the surface. I dont think the oil will evap no matter how much it is diluted but instead it must be flushed off of the eng.

Yes...

Areas I didn't like, I hit with RustMort...


'Engine Primer', followed by rattle-can Mopar Perf. Hemi Orange...


Doing well after 20 years...


(Of course, if I could go back, I'd a had it burned, and tumbled...

The end result is a nice canvas...)

"street hemi orange" or "race hemi orange" ?. that street hemi orange looked like 318 red with God know what mixed in, terrible. the race hemi orange was somewhat close & someone mentioned that there was a Krylon or a brand like that (cant think of the name) that was very very close to the OE BB orange. EDIT Rustoleum maybe

'Street Hemi'...

Back when I sprayed this engine('93), the color was real close...

No complaints...


A friend talked-up Plasti-Kote in the past...


Now TODAY, I'd look at other options...

Paint's changed a lot...

I've used Eastwood's "Chassis Clean" on two engine blocks with great results. Couldn't be happier with the stuff. When done, I had absolutely no residue and no issue with primer or paint lifting. Its cheap and in an aerosol can so you can spray blast it. Spray, scrub with toothbrush, repeat. Then wipe down with a clean rag. I love this stuff. I use it to clean all kinds of things. It will even take paint and grease off plastic without hurting the plastic if used carefully.

At the point you have the block, I would fill a paint gun with lacquer thinner. spray it down a couple of times and paint it....

Block was baked and shot blasted.

Then the minor oil that ran down the side during assembly was cleaned off with brake parts cleaner and then wax and grease remover.

Plasti-Kote #226 Chrysler orange covers well and holds up way better than anything else I've tried.

Once you've gotten the majority of the grime off a good final rinse with Acetone and a big stack of clean white lint free rags works great, follow up with a wash down with metal prep (the type that leaves a phosphate coating like Eastwood's "Ospho") rinse with water (I use dripping wet rags) until the stickyness of the Ospho is gone, then let it air dry. A nasty looking white film will be apparent when it dries, this is the phosphate that protects the metal from rusting short term. Once dry shoot paint directly over it, works great!

Well, you're only at the beginning of the block prep...Depending on what I see IN the cooling passages I treat it to a muratic acid cleanout...After I'm happy with the de-rust/de-scaling...I use Eastwood's oxysolv or Ospho as Scott has suggested...That makes for a nice,clean block the paint will easily adhere to...

That is NICE!

Yes that's the one I was thinking of earlier that I had heard rave reviews on from several parties

Another vote for wax and grease remover and brake cleaner, then Plasti-Kote Chrysler Orange engine paint.

Almost 10 years and mine still looks great.

I used the method I described on these two. Paint was Frank Badelsons, gun sprayed over bare iron. I have painted others the exact same way (using Franks paint) starting in the early 1990's, it works VERY well if you are thorough in the details. The high gloss shine that Plasticote and others may offer might look "pretty" but if you are attempting to be as original as possible you don't want that super high gloss look, just depends on your goals.

Get a couple of cans of good spray brake cleaner, I buy and use Wal Mart brand brake cleaner and carb. cleaners for my shop use Spray the block off several times really well with the brake cleaner, then use a good heat gun and dry the block, or whatever other cast iron your going to paint with the heat gun, hold the heat on the cast iron in one spot until you see the moisture come to the surface and then evaporate, work your way over all the surfaces you want to paint twice drrying them out, it will take less time to redry the block on the second go around , and then shoot the paint to it Let us know your results, if you do it this way

bunch of different methods here, thanks everyone. just have to pick one and go for it.

scott, i have badelson's paint as well, and plan on spraying that. once i get it cleaned up, i'll be good to go!

Back in the day I used oven cleaner, let it sit over night, came out very clean.

Oven cleaner, then Dawn blue soap.

What percentage (cut with water I am assuming) and how long do you let it cook?

Iron is porous and the best way to remove oil/grease from it is to bake it(Best way)or heat it with a torch/heat gun if you're doing it at home.......You can take a block fresh from the machine shop and go over it with a torch/heat gun and it will sweat oil residue from the iron....which is what lifts the paint in the first place. We're not talking "Red Hot" here, just warm enough that if there's dirty iron it will smoke......about 10 minutes with a simple propane torch will tell the story. After that you have nice warm block ready for paint. Spray on cleaners work but they mostly clean the surface. Some shops have better equipment than others, but I always sweat the parts first to make sure....medium coat of paint to seal it off....assemble the engine...final coat of paint....Done.

1,1,1 Trichloroethylene is carcinogenic, 1,1,1 trichloroethane isn't. http://www.cdc.gov/niosh/npg/npgd0404.html

So you're wrong about that. It is listed as an ozone deplete, so I must ask if you have ever disconnected any emissions controls on your cars, because that causes air pollution which is much closer to home, the earth's surface.

This whole subject is moot, however, as the Montreal Convention banned its production starting in 1996.

R.

Well thats good to know. The chlorinated brake cleaners dissolve oil faster, but I try to avoid them usually because I always thought it was a carcinogen (confusing with trichlorethylene). I notice it does tend to leave a residue though, vs the non-chlorinated cleaners. It does do some funky things to latex gloves too.

Let's not forget what it does to your fingers! It sucks all the oils out of them and for me at least it burns like mad.

R.

After I re-read the original question I realized it's in a longblock form already... I usually use the muratic acid if it's a bare block and the hot tank did'nt get it like I wanted...I'm not sure I'd do it with an assembled longblock...I put the block on an engine stand,plug holes, and start pouring...Let it cook for a while{until it looks like it's not doing much more} and drain it....You would'nt believe what comes out of a "clean" block...Turn the engine to a different position and repeat...
I'll have to check on what strength{there's different concentrations} I have in the gallon containers.. I just used it straight last time...We have to do this to our fishing boat every few years to keep the sea water passages open it really cooks the debris out...

Makes my fingers tingle, and yes, sucks the oil out and gives you dead/pealing skin like when you're in the water too long!

Exactly!
The solvent suspends the contaminants and they must be removed in suspension or they just lay back down when the solvent evaporates.

I agree with the grease and wax remover. I've painted blocks in the past using brake clean, carb cleaner, lacquer thinner. It all evaporates to quickly. We always use single stage urethane. The only thing that seems to harm it is the dye from race gas can stain it. Everything else won't touch it. I'm not afraid to use bondo either, holds up perfect unless it's close to the exhaust, IE BB valve cover with stock manifolds. You'll notice my heads have no casting roughness or Indy logo. I have a bondoed factory cross ram that has the same finish as the engines in these pics that was bondoed and painted over 15 years ago.

For a dead on perfect job should a person use the cleaners then sweat the rest of the oils out with a torch then reclean OR torch then solvents? (OCD)

I really enjoyed this post. I'll tell you what I use. I hit greasy stuff with mineral spirits to loosen up the stuff in the cracks and crevasses. Then use compressed air to evaporate the residual. Then I hit the parts with POR Marine Clean (spray bottle) and a clean brush and rinse. This stuff will strip the [censored] off a sow and is fine for you and the environment. Just wear rubber gloves and a mask cause it will strip your skin oil and burn a bit in higher concentration. even 10:1 it's amazing.