engine painting MASKING question

I have been searching around, and I see some people paint their blocks without masking the gasket surfaces, and some mask them off.

Is there an absolute need to mask off, say, a water pump gasket location?
Should it be bare metal, or not?

 

Usually I plug the holes with aluminum foil, do my painting, then clean the gasket areas with some fine sandpaper. I wouldn't take a chance with paint between the gasket and mating surface. like that old saying goes" an ounce of prevention..."

 

I use masking tape and then cut it away with a razor blade using the contour of the boss prior to painting, that way I have a nice, clean bare metal surface for gasket to mate to.

 

I mask them off.

Companies like Summit sell bolt on plastic covers as well.

 

I've done it both ways. But I do some stupid shit. Both work.

 

some stuff i put together first then paint...like the factory did.

 

there is no good reason to paint a gasket surface. You can't leave the paint on there and expect a good seal, and painting and then scraping/sanding is a bit more time-consuming than doing a good job of masking them off. I run bolts into any holes of any kind, then take them out when I'm done. Any bolt holes that are not used get stainless cap screws Loc-Tited when the block is done.

 

I usually mask off the gasket surfaces with either good masking tape or Contact shelving paper for the big surfaces (head gaskets, etc) -and I trim the paper with scalpels, the non-sterile versions that are available from jewelry tool suppliers - they're way sharper than xacto's or utility knives and seem to last longer.

 

hahaha

me too

 

some examples of a flathead I found. Made me wonder why they did it like this.

 

We always paint the engines as separate pieces and assemble them after the parts dry. That way there is no paint over the gaskets and if you have to ever disassemble the motor the paint doesn't chip at the mating surfaces. We mask any area where two parts are going to be bolted together.

As for the bare areas where gaskets go, we use blue tape and cover the whole area then use an exacto knife to trim just slightly inside the edge. That way the bare machined areas stay paintfree and you get a good seal when you put the parts together.

I also like a motor to look like a motor, so I leave the gaskets show, rather trying to hide them.

Don

 

Masking tape is cheaper than my time to scrape off paint.

 

Mask over the mounting surfaces and run around the edge with a razor blade or xacto knife. I usually stay about a 1/8" in from the edge just so I don't end up with bare steel showing. Somtimes you need to look at the mating part to know where to cut.
This is the easiest and fastest way I know.

 

I have always masked off in the past, but seeing this a few times made me wonder why.

 

I like to plug the holes and or mask close to the edge. If you do get paint on the mounting surface (I did when I was touching up a spot near my water pump) you can use a 3M scotch brite roloc disc on a small right angle die grinder to remove the paint from the mating surface. I use the 3M pads on all my mating surfaces any how.

I also saw a tip here on the HAMB once where a dude masked off the surface and lightly tapped on the edge of the machine surface where the tape hung over with a small body hammer and then pealed the tape off of the other side and it left a nice clean cut right to the edge...I tried it once and it worked pretty well. its alot faster than the razor blade and leaves a nice seal so that paint doesn't bleed under the tape.

 

I usually mask the surfaces somewhat. If any paint gets on a sealing surface I use lacquer thinner. Preps the surface for ass'y also.

 

Good point I always like to prep with thinner as well!

 

Why would a coat of paint stop a gasket from sealing especially something like a water pump? Some very good engine builders used to spray their head gaskets with aluminum paint and swore it made a better seal. I'm not saying masking is a bad idea but I would like to know if anyone has tried putting gaskets over paint and what happened? My guess is nothing.

I know Detroit used to paint their engines after assembly but before installing the carburetor, fuel pump and hoses. It didn't seem to hurt anything.

 

A little paint won't hurt, most people want a good looking engine on the stand so their buddies will "ohh and ahh" while it sits there for God knows how long.
Part of having an "Oral Rod" it seems.

 

I generally mask large surfaces with spare heads , intake manifolds etc. as long as their not hard to paint around .

 

I always mask off the block's deck and head sealing surface. The rest I don't sweat and never had leaks

 

i mask any part that is going to get a gasket. and put bolts in all the threaded holes before paintin.if the engine has the heads on it already i put in old plugs and old vc on it.when im done and ready for it to go in the car i grab a artist brush and paint and paint anything that still show bare metal.

 

I mask... why put more there on a surface that needs to seal...

 

I buy a good running engine, never take it apart, clean it and spray bomb it... drop it between the rails ... DONE !
OTOH mine's a driver.

 

That might of been me, I like to do it that way.