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I was wondering if anyone has used Glyptol Paint to paint the inside of
there transmissions ,transfer cases or engines ? I have been reading that
some engine builders use it to put a smooth surface on the oil gallery's,
and others use it in there rebuilt tranny's and transfer cases to seal the castings
and make the oil flow easier. I have use Glyptol before but only as a
electrical insulator. Has anyone have any thoughts on this ?

Sal

It does a good job in gear box cases, but be careful using it around oil galleys;
some are small and it's easy to clog them and restrict oil flow.

As Charles pointed out, don't over do it. I have used it on all SBF and SBC V-8s since the 70s in the lifter valley. Sometimes also on the cylinder heads before I reassemble. Never did a transfer case but did trannys, rears, and even the rough casting on the sides of a V-Twin motorcycle. De-grease really well and put in a warm dry place to dry, or be prepared to wait as you have the same humid climate as I do.

Thanks guys

Sal

An old topic, but still relevant for anyone doing a total rebuild of a transfer case, transmission, steering box, etc.

Painting the inside of a cast case with Glyptal is a commonly accepted practice to prevent oil weepage through a porous casting. And yes, cast housings (iron, steel, and especially aluminum) can be surprisingly porous. But before the casting is painted, it's good idea to thoroughly degrease them, and then bake them to force any oil out of the casting. If you don't believe that a casting can "absorb" oil, here's what my handbrake mounting bracket looked like after four hours at 260degF. This part had been degreased in a solvent tank, then glass bead blasted, and then treated with a phosphate etch, so there was absolutely no oil residue left on the surface before the baking. But cooking it forced the absorbed oil to the surface (and also through the fresh Glyptal paint on the inside ).

If you look closely, you can see that the porosity started on the inside of the casting, between where the oil seal and the bearing would be (where the red Glyptal paint is in the second photo), and traveled through the casting to both the front and back faces.

This seepage can ruin the finished paint, and it can be frustrating trying to track down the source of the leak.







Caution: if you're going to bake painted parts, and Glyptal recommends baking for two hours at 257degF, don't use the oven for food preparation ever again. Glyptal fumes are nasty stuff. Used kitchen ovens can often be found on craigslist or in the classifieds for less than $50. But you will need a 230v outlet; I changed the plug on the electrical cord of the oven I use, and plug it into my shop's MIG welder outlet.

Hi Guy,

This is one of those topics that to me I think needs some common sense applied to it. And although I hate to go against the grain on this one, my common sense says no. I know it's used in race engines, which are routinely torn down and inspected, but if it was needed for the everyday auto why don't the OEMs do it? Why doesn't EVERY engine rebuilder do it?

The idea of painting the inside of an engine, which has small passageways for oil, is hot/cold cycled thousands of times, and probably won't be looked at internally for another 30+ years just doesn't sound like a smart thing to do. Think about the claimed advantages.........it increases oil flow back to the pan. Is the oil just hanging onto to sides of the block for dear life? If you need to have your oil get back to the pan a few milliseconds sooner I'd say you have a much bigger problem. Seals porous castings. As Elwood demonstrated with that part he baked........what do you think will happen to paint that has oil trapped below it in the casting as it heats and cools over and over for many years? And where exactly would that paint go when it flakes off the casting? Obviously the problems would be much worse in an engine than say a gearbox, or maybe not........at least in an engine the oil gets changed.....unlike a gearbox or differential. Do the race guys paint the insides of their powerglides and TH400s? (I really don't know)

I've got a good friend who's an engine builder and his thought is that there are too many things that could go wrong that outweigh the claimed benefits. I tend to agree. Maybe with a brandy new casting it might be ok to use........but something 65 years old? I think the preparation of the part is so critical that I'd be afraid to use it. Now there are some folks out there who are incredibly fanatical about every detail of their work, my Dad is like that, but most folks just aren't that way. So if I was buying a car/truck/insert whatever motor vehicle you want, and the previous owner told me he painted the inside of the motor with Glyptol..........I'd be more concerned than if he didn't. So to me that says no, I wouldn't use it.

Just a different perspective from what's been previously posted. And Elwood..........thanks for posting those pics! Very interesting.

regards,
bob

Actually, I did not mention painting the inside of an engine block, specifically because of the potential for obstructing the small oil passages. Transfer cases, manual transmission cases, steering boxes, etc. do not have those passages, of course.

One other reason that most OEM engine manufacturers and many rebuilders do not paint the inside of engine blocks is because the cost of doing so far exceeds their benefits. Block preparation for internal painting is time consuming, and most users won't notice any benefit from the process, so they're unwilling to pay for it. That, and casting technology has improved considerably from when our M37s were manufactured. Some OEM engines were painted on the inside - I think International-Harvester painted theirs? Maybe that says more about the quality of their casting process than it does about their attention to detail, and the painting was a band-aid to fix a recurring porosity problem?

I don't know if the race guys paint the insides of their automatic transmissions. Casting porosity may not be a big concern to them, since the parts get torn down so often. But I do this because I hate leaks, and applying Glyptal to the inside of a transfer case housing casting is a proven way to prevent weeping.

In these Chrysler 230 flatheads, there might be some benefit to painting the tappet gallery, which has a very rough finish from the sand casting, and low spots that trap oil sludge. But since there's no valvetrain in the head, there's nothing to paint there.

If the surface is properly prepared, and the Glyptal is correctly applied, it will not flake off.

Your question about the oil trapped in the casting is a good one, and why I noted that the part in my photos has already been baked for four hours (two more than the recommended Glyptal curing time). It's a process of baking, then cleaning, then baking, then cleaning, until the residual oil stops surfacing. Only once I'm confident that the trapped oil has been purged will I put a top coat on the part.

Obviously, what I'm doing here is not for everyone, and I do this work only for my own use, not commercially. But for those who derive pleasure from taking a greasy, defective assembly and making it better than new, this process might be of interest. It's one of the reasons I enjoy working on my M37.

My brother spent a few decades rebuilding industrial engines. They all got Glyptol. As do all his personal engines and mine. We have never had a problem with it nor a failure. But, he is nitpicking and fiddly in his work and everything HAS to be perfect before it can go out the door. (He was eventually let go because the bean counters at the time could see no value in his precision. They return rate in the decade since he was made redundant, has soared and they want him back.)
I love this stuff in drivelines and believe it helps keep the oil/engine cleaner as it helps to eliminate places for sludge build up.

http://www.glyptal.com/

I'd use it on older gearboxes, for sure, not sure about a modern engine though!

CD