'61 Intake manifold madness

[MidModCad]

So I pulled off my 390's intake for a trip to the sand blasters tomorrow. Got a few questions rattling around. The passages will be open during blasting. Even if I blow it out afterwards might there be some residual stuff caught inside there that could eventually make its way into the engine?  If so, is there a way to block the passages?  Also, should I remove the brass vacuum fitting in the rear?  The holes are small, but material could get blown in there.  Lastly, the gaskets I pulled off are steel, while many of the gaskets I see for sale are not.  They can't be reusable can they?  If not, what are the best brand to buy?  Thanks all.

[Gabe Davis]

When I rehabbed the top end of the 390 in my '59 I came across the same issue. I ended up just using paint stripper to remove what was left of the original paint. Surprisingly it came off very easily. Made sure the grease was all thoroughly removed and knocked any surface rust off with a steel wire brush. I hit it with some self etching primer and then topped it with the correct Cadillac blue from Bill Hirsch.

https://www.hirschauto.com/AEROSOL-ENGINE-ENAMEL/productinfo/EEA-SPRAY/CAD%20DK%20BLU/

I wish I had known that the butterfly on the drivers side exhaust was stuck shut as it caused a lot of it to go through the heat riser in the manifold and prematurely burn off the paint in that area. But other than that it looks great. It probably would have brunt off there eventually anyway.

The gasket set I used was steel. Fel-Pro if I remember correctly. I used some indian head shellac gasket sealant between it and the heads and the manifold to help seal things up. Worked great.

[Gabe Davis]

Found some pictures. Shows where it started, after prep, after paint and re installed.

[The Tassie Devil(le)]

There will be no trouble in blasting it, just cover the gasket-sealing areas with masking tape to protect the surface so that it doesn't accidentally get blasted too much.   Some sandblasters don't actually use sand, but a harder grit, which could actually scour a gasket surface.

As for cleaning it out, just wash it completely, inside and out, then dry with either a compressor, or let it air dry.

And, remove all fittings, so that when they are reassembled, they will have no chance of leaking.

When I get my manifolds cleaned, I am usually rebuilding the engine, and get then dipped into the caustic solution that the reconditioners use when cleaning the rest of the parts, block, crank, etc.

Bruce.

[MidModCad]

Thanks! Good tips. Looks like my manifold has had 4 coats of paint at various times in its life with layers of grease in between so sand blasting is my best bet.  I'll tape the heck out of the ports and follow up with a good clean (won't water begin the rust process on top of bare metal?). Bruce, I think it was you who mentioned that paint on the heat tubes usually cracks no matter how carefully you prep, so I'm considering hitting those with some high temp black. That way, when I need to touch up later I won't need another can of pricey Hirsch blue. Not exactly a stock look, but think few will notice.

[Roger Zimmermann]

While the manifold is out, check the hot air tube for the choke. If it was not replaced before, it's certainly broken by successive heating/cooling.
If you buy the manifold gasket by Best Gasket, you will get a thicker gasket better suited for repairs. Of course, the steel gasket you removed cannot be reussed.
Finally, before you install the manifold with the gaskets, put it on the engine to verify that it's not warped. It's not easy to check but can avoid sucking false air once the repair is done.

[The Tassie Devil(le)]

..........(won't water begin the rust process on top of bare metal?)....... 

It will if you leave it totally bare and leave it in a dank area.

What you can do is after the blasting, liberally hit it with the WD40, or other compound till you are ready to paint, then wash it off and spray with Brakleen to remove all residue before colour painting it.

Whenever I "dip" an engine/parts to clean it up prior to machining/rebuilding, it might be months before it is ready to paint, and never had any rusting issues.   I only degrease it the day or hours before painting.

Don't forget  that one cannot mask up a dirty/greasy engine.

Bruce.

[MidModCad]

As the kids say, "true dat."  I plan to paint the day after I get it back and our weather is hot and dry so things should work out well.  My choke tube is in good shape (I just restored) and I've haven't had any vacuum leaks.  Also, the ports have a nice even mark where they sat on the gasket.  The heat ports do have some mild buildup though, and I'm not sure how to remove whatever residual doesn't come off at the blaster.  Any suggestions?

[MidModCad]

Bruce, do you have a good way to clean the inside?  After blasting, there is still residual sticky film inside the ports that now has fine dust sticking to it.  And it goes deep - throughout the manifold.  I'm scratching my head how to clean it out.  Here's a pic.

[savemy67]

Hello MidModCad,

If you want to thoroughly clean the sticky residue and the dust, you need to flush the passages.  The sticky residue is most likely gasoline "varnish", built up over the years.  You will need a strong solvent like acetone to remove this residue along with the dust.

The inside of the passages are rough due to the nature of the casting, so the inner surface holds on to whatever passes through the passages - in this case, atomized gasoline.  You will probably need to do a little mechanical scrubbing with a bottle brush.

You can get a plastic mortar pan, and about three gallons of acetone, and make your own dip tank.  This is relatively expensive, but it works.  You need to do this outdoors, in a well ventilated area.  Acetone is very volatile, and will clean the iron so well, that if there is any humidity in the air, the surfaces of the manifold will start to rust in a few minutes.  Be prepared to apply primer to the manifold immediately after cleaning, and seal off the carb and head intake ports with masking tape.

Respectfully submitted,

Christopher Winter

[signart]

You need to do your cleaning & degreasing before the blasting. I use beads on intakes instead of sand as it smooths the iron or aluminum while removing paint and rust so as it is easier to maintain once painted and installed. I wouldn't want any oil or grease to touch the surface after the blasting before painting. Oils will saturate the cast and be difficult to remove completely causing less long term adhesion for the paint. A small amount of surface rust would be less likely be a problem.
Also, I use Gorilla tape to cover the ports where I don't want the abrasive to enter. It repels the media from penetrating the tape.

[MidModCad]

Your assessment sounds right on, Christopher. Would a bio-degradable industrial degreaser like Purple Power work as well as acetone if scrubbed hard? And painting right away was my plan, but what about removing residual acetone on the outer surfaces? Maybe that's where the degreaser comes in. On the primer front, Hirsch Paints recommends not using any with their product in order to keep the final coat thin and lessen heat buildup. What's your take on that?

[The Tassie Devil(le)]

Another way to clean out the insides is to take the part to any engine reconditioning shop, or even a radiator shop, and have it dipped and soaked in their caustic tank.

It will save you a lot of time, and not to mention the mess, and disposal of the end contaminants.

Bruce.

[MidModCad]

Hmm.  I'll check into that.  Thanks.

[fishnjim]

2 separate processes, degreasing and surface prep for painting.
Purple will cut the grease but may need repeated applications and a stiff scrubbing brush.  Spray it on neat first, let soak.   Dawn dishwash detergent works good too.  Put on full strength, scrub, and wash off.   Repeat, if needed.
There are many commercial cleaner products that do this, GUNK, being the most prominent.
I would NOT recommend large scale open acetone, it flashes too fast and is quite the fire hazard.   Tough on the skin and lungs also.   Plus unless you have industrial supply, it'll be ~$10/gal at the bigbox.   I'd save that for the final wipe down before prepsol/tack.
Another one is 5 gal carb cleaner soak or parts cleaner.   If you're so equipped for such a large piece.   
I use bead cabinet mostly for old paint/surface rust removal and of course have compressed air to blow it out.   Don't overthink this.   You don't want to have much grease/oil around going in (degrease first).   The media will stick and not flow.   OK, if you're ready for a media change - after.   
Caustic "boil" was/is the common method for large scale iron cleaning, preferable over acid dipping.   It's less favorable on the small scale due to problems with hazardous solution disposal.   If you have a local dipper, maybe a good solution for you, no pun intended.

[MidModCad]

Great suggestions. Since the manifold has already been blasted I was considering letting Purple soak in the passages for a while then scrubbing like hell with a long stiff dryer brush.  If I went with having a shop boil it out what prep is best for paint when I get it back?

[signart]

If it is already blasted, it is ready for paint.  I would get some paint on it asap. Anything else touching it is contamination, including your fingers. After curing, the paint will be protected from oil, gas, grease and cleaners.