Painting the inside of the engine block

[Captain D]

I read in AutoRestorer magazine (May 07 and Aug 07) that since the 1950s some engine rebuilders paint the interior of the engine such as the area of the cylinders for 3 reasons. First to help the oil drain back into the pan quickly, second to prevent sludge buildup and third because the engine is a casting and over time sand particles would come loose and could take out a bearing. They use rustoleum gloss or epoxy paint. It seams to me that the risk of the paint failing and clogging up an oil passage would out weigh any benefits. Any thoughts or comments on this would be appreciated.

 

[bluetlr2001]

Ive not heard of that but i have heard of them painting under the intake of v-6 and v-8s because it helps reduce temps. But were they paint it it has no moving parts touching the painted area. i think if you paint the cyclinder area it may cause problems because the rings will scrap the paint off. It want last long plus if it doesnt burn up in the cyclinder it will eventually wind up in the oil and the rest of the motor

 

[talon20g]

Well captian d I did this to a previous motor and eveything ran fine and still continues to as far as I know. My old man told me about this. Also I haven't tried this but some of the old v8 guys use the vaccum pumps off old caddy, olds and such to zero out the crank case pressure. In other words the PCV (positive crankcase pressure) isn't positive anymore it's neutral. This is supposed to increase gas mileage and horsepower by decreasing the amount of extra work the piston has to do to overcome the positive pressure. These old farts were creative and always thinking outside the box.

 

[Defiant]

This dates from the fifties, and possibly even earlier. But like so many "tricks" done by racers, they're done on motors whose life is expected to be a few hours or a few hundred miles- in the case of dragsters, maybe only three miles at the most. I'm not trusting enough of paint standing up to the temperatures and solvent abilities of crankcase oil and the vapors in that space.
As for the idea of a layer of paint "sealing" in "trapped" casting sand, this has to come from someone who's never been to a foundry and seen what a vibration table does to green castings. Suffice it to say there will be no sand "trapped" anywhere.

 

[adiffrentcity]

There are many high tech coatings available for interior engine surfaces from the block to the pistons and many companies offering them. The difference between them and paint is that the high tech coatings are engineered to increase lubrication or cooling or to decrease heat transfer. Paint is engineered to cover something. And while I can see the potential benefit of quick oil drainback, this would also reduce cooling from oil flow. Think about the fact that products like water wetter work by reducing surface tension of your coolant so it will stick to engine block surfaces for more heat transfer. It would seem like you would want your oil to do the same thing. One of the sites below talks about using oil shedding coatings on your rotating assembly, but I don't know if paint would cut it. It's your choice bottom line, just seems like a waste of paint.

More info:
http://www.hpcoatings.com/products/lubritic.aspx#pec
http://www.swaintech.com/store.asp?pid=10321

 

[Sharadon]

I've seen many painted engine blocks. It's very common on Hemi blocks. The heads don't drain back fast enough in high rpm race applications. If the block is preped right the paint stays on for yr's without any issues. Other internal coatings also work well for oil drain back, but never on the cylinders.

As for vacume pumps. Not really a street car item. They do help make power, but are used mostly on race engines that use low tension rings or big cube long stroke engines with windage issues from a big crank.
Yes, creating a vacuume in the crank case will help free up a few hp. But it's only a few. I've heard of as much as 20hp. But that was on a 500cu high compression race motor with low tension rings and 7500rpm