So I'm getting close to hacking up the oil pan on my Subaru engine to give more ground clearance. The stock pan was painted/coated with a great, durable, smooth finish. I've alread got that blasted off. I have no idea how they got the insides, including the oil pickup tube, underside of splash tray, etc. painted unless it was dunked.

I'm going to cut the bottom and braze on a shorter, wider pan (with baffles) which I plan to make out of mild steel. The outside I plan to powdercoat. But I don't see any way to get the insides covered. Is it okay to leave this surface untreated ? On the one hand, it's gonna be spalshed with oil, which protects against rust. But OTOH, I know motor oil can get moisture in it if the car is driven on short trips (which I do) and left to sit for long stretches (which I do), and also that blowby can deposit some real corrosive stuff in the oil. And the mild steel rusts in the blink of an eye. I filled a small mock-up tank that I built with water to look for leaks. Within hours there was brown rust forming.

Any sage advice from the old-timers ?

Some of the "OLD" time hotrodders would paint the inside of there blocks and

pan. What kind of paint I am not sure but you should be able to get that info

from a paint shop or engine builder.

Not an old-timer but i'll tell you what I did...

I powder coated mine and was able to get _most_ of the surface coated. I have a strong feeling that the original coating was powder as well. That being the case, you can probalby powder coat it before you put it back together, then strip off just where you are going to weld, and then when its together re-powder it. It won't harm the existing powder, and you should get complete coverage.

Mine has some bare metal surfaces inside, but I tried to keep it to a minimum.

Good luck with the mods. Be especially careful with the drain plug hole. I ended up having to braze a couple spots on my pan, but it seems to be doing a pretty good job so far.

-Tony

Glyptal.

I would not bother with paint inside - too much risk of it flaking off for little to no benefit (it should be covered in oil unless you let it sit for waaay too long).

Well, here's the thing. My plan is to braze the pan. I'm pretty new to the ways of the torch, and I figured brazing is a lot more like soldering - and so easier for me to get the hang of. The few times I've messed around with welding I've blown through stuff much thicker than an oil pan. I've done a little practicing with brazing and I'm starting to feel pretty comfortable with it. The only real downside is that the parts get a lot hotter and I'm sure just about any kind of paint/powder would cook off.

I'll check into the Glyptal (name sounds familiar). As for leaving it uncoated, I'll watch the polling numbers.

Not nececelary since many bar metal surfaces are found in the engine.

Don't bother painting the inside of an oil pan. You are just inviting disaster with flaking. Most oilpans are bare steel. They are even bare steel in MARINE engines where corrosion is MOST likely, and they do fine without. Just keep oil in the engine.

Glyptol is used to paint electric motors and the windings. I would not paint the inside of the pan. Just clean it really well.

Okay, the early returns are in - no paint. I'll just hit it with WD40, since it could be a while before the engine gets cranked.

If you are going to store it for any length of time without oil in it and you want it to remain pristine, I'd coat it with something more substantial than WD-40. Machine tools are protected by Cosmoline or BOE-Shield.

Boe Shield

You can clean if off with cleaning solvent. WD-40 produces such a thin film, it's almost useless if you get actual drops of water to lay on any surface and you want it absolutely pristine (like the ways on a lathe or milling machine).

Don't mean to sound alarming, but what I have been taught is that blasting with sand or grit should not be done on engine parts that have tiny blind spaces brazed together. What can happen is , them blind tiny spacees can trap broken bits of sand (from grain of sand to dust sized). They can come out and hurt the motor.
This tip was re-enforced by a well respected engine builder for 356 engines, Harrey Pellow. r.i.p. in some 356 Registry articles. he had examples of engines that failed because of sand released on oil system parts that were blasted. (things like the oil cap filler "can", filter canister, pick-up tube).

Better to try a chemical paint stripper.

Basically the it is an issue with sheet metal parts formed from more than one piece using: welds, rivits, brazing to assemble it. Pay close attention to joints, and seams. if if your pan has open seams (ie not filled with weld or brazing) it is all to easy for the high velocity sand to wedge itself deep in a seam, only to come out later. sand gets everyware..

The oil pick-up tube could be brazed to a plate for instance, and the braze looks all fine and dandy on the outside, no tiny voids to trap sand. Often is the case that the inside of the pipe is not brazed, and there is a gap. The sand at velocity will ricochett many times at speed, until it gets stuck in that gap, and you can't get to it to remove it. That is the issue with blind spaces, and open seams

if you can can see all the seams and joints, and confirm they are wleded, or brazed solid, no gaps, then you should be resonably safe, assuming you complety clean it at least three times to be sure. use bottle brushes and such to scrub all surfaces. So get your bright light and inspection mirror and pray there are no open seams, or jonts.

if you have open seams and joints in this part, consider getting a new pan, small price compared to a sudden oil pressure drop six months down the road. Grit needs only one pass to wedge in the bearing or piston, and it will gouge away.

You can clean it then try this: over a big clean sheet of white paper, or a mirror bang part with a hammer near any seams, upside down, to see if any grit falls out to collect on the white / mirror surface. if any comes out, I'd be inclined to toss it. Then again, if none comes out, is it still wedged in there? Heat and vibration can make it come loose at any time later. This 'test " must only be done with a DRY oil free surface on the part. If pan is oily, you'll probably pass the test no matter what, 'cause the grit will stick to the oil.

A good coat of un-peeling paint using a dip for application (roll it to cover all inside surfaces) could be used to mitigate any open seams/joints, the paint if it remains bonded will seal and trapped grit in place. Normally I would not paint the inside of a pan, (for reason that paint might chip off) but in this case it may be advisable if you wish to re-use the pan after blasting/grinding. figure paint will do less damage than sand grit, and the paint is supposed to stick (if right stuff applied properly)


Remember that when your heads get blasted, they dissasemble them, and blast one monolithic piece, same with blasting an engine case. the problem is the sheet metal assemblies that have open joints/seams.