Engine Internal Painting--Thoughts?



I'm trying to decide: coat the crankcase internally? Or leave it "as cast"?

Coat--The classic is GE electric motor paint (I forget the name, but Eastwood carries it), and the more modern process is an oil-shedding applied polymer coating--Polydyn Coatings http://www.polydyn.com right here in Houston has done many, many race motors, and they will be be applying this coating to the crank and rods on this motor as an anti-windage measure.

In either case, the idea is to aid oil return to the crankcase, presumably speeding oil cooling, and to seal porous areas and loose crap. Speeding return to pan makes sense, as external oil cooler(s) are part of the program. I doubt there will be any crap in this motor by the time I reassemble it, and porosity? Mmm...the block came OEM painted internally!

As Cast--Adding a coating of any sort adds an insulating layer, AND smoothes the roughness of as-cast, filling in the "valleys" and leveling the "peaks", thereby reducing the surface area and available BTU radiation area.


Grumpy Jenkins used to paint the insides of his engines black to absorb heat and the outsides white to radiate it. IIRC he used "Glyptol." Of course, the Grump was only concerned with max HP production and expected engine life between rebuids was 1 weekend or less.

Personally, I'd skip the crankcase coating completely. You're got enough oil in the engine to guarantee adequate lubrication, especially if you've put in a windage tray, so the rate of drainback is not, or at least should not be, an issue. All the oil that runs slowly down those rough uncoated crankcase walls is going to give up a lot of heat to the block, which is a good thing. Effort spent on maximizing the iron to water heat transfer part of the cooling system would seem to be more productive although with external oil cooling that probably matters less.
"Glyptol" is the exact glop I was pushing my one remaining brain cell to remember :oops:

I DO think that an an oil-shedding polymer coating on the crank throws and the rods is a heckuva good idea.

There are several SCCA H Prod (950 Sprite guys...but you knew that!) who have the entire crankcase of those motors coated, a little overkill for my purposes.

Those empty blocks are cool to look at, tho.

Typical HP engines run 12-16 hours between rebuilds and need all the output those pathetic little BMC A blocks can produce. Are they trading longevity for power? I know they would make that trade in a heartbeat.
8) properly prepped there is no question of durability. the key here though is "properly prepped". the block needs to be imaculately prepped, otherwise the coating can flake off and absolutely destroy the bearings. i have seen that happen on race motors. for the street, the benefit you gain is negligable at best. i wouldnt waste the money. on the other hand, you can use a grinder to smooth the internal surfaces of the block and all you spend is time. just remember to tank the block when you are done to remove the grinding remnants.
Some random thoughts on engine heat and power gleaned from a vaiety of sources.

Windage represents a dead loss of HP, anything that reduces it is good. Whether the coatings are worth the cost on the street is debatable, but none of us much listen to reason when it comes to our toys, so why start now?

Heat flow is dependent on temperature difference. The hotter the block, the less combustion heat will be lost to it, the more power the engine will theoretically make. The downside is that even without being carried to extremes this reduces the life of all components involved, sometimes massively.

On most engines max power comes at a water temperature of 220-230°F, a bit warmer than some of us may want to run on the street, and drops off radically below about 200°F. The 195°F EFI thermostat turns out to be a good thing after all. The rest of the engine has to be built to accomodate elevated temperatures though.

Most stock cooling systems do a p**s-poor job of cooling the head in general and the exhaust valves in particular. A lot of inline engines starve the coolant flow to cylinder #1 and need corrective baffling. Some race engine builders solve this by reversing the coolant flow so that the head is cooled first. This allows higher CRs, cooler, denser intake charges and less heat lost to the block. On a street engine this may not be worth the effort and expense, but careful use of a pyrometer to find hot and cold spots and add or remove baffling as necessary will produce a stronger and more reliable engine. The radiator should be large enough to cool the water by 40-60°F inlet to outlet.

Hot side oil temps with synthetic should run between 212-250°F. Below 212 and water condensate is not boiled out, above 250 and the oil breaks down. Dino oils should be limited to something less, maybe 230 (?) Synthetics not only have higher temperature limits, they provide better lubrication and they aereate less so thet provide better return flow and have much less tendency to fill the valve covers and force their way past the seals.

All of this was derived mostly from race engines which live in an abusive but predictable environment. For a street engine the environment is anyhting but predictable, so trading some efficiency for a few degrees of wiggle room is probably a good idea.
all im thinking here is ive never even heard of the idea of internal painting. im thinking of how cylinder wall lubricatino works, the oil sticks to the cross hatch. now from workign on boats i know how good of a sealer oil can be, ever heard of a labrynth seal?. my thought here is that the oil thats on the rods and crank actualy stick to and absorb into the pourous and unsmooth surface. that alone should be enough to allow adequite drain of for an externally oil cooled engine. if you already have your mind made up to go fro the painting obviously your gonna do it. i personally would spend the money on somethign liek oil passage enlargment or some other thing to benafit the oiling system.
I'm not going to paint or coat the engine block/crankcase internally; I simply wanted to get as many opinions as possible, as much input while this mess is still in lotsa pieces--I want to incorporate as much trickery as I can!

My basic concept of this motor is to enhance efficiency and durability in any way I can.

Heat is a HUGE factor, affecting both efficiency and durability. Basically, I want to keep as much heat energy as possible inside the combustion chambers, exhaust ports, exhaust manifolds, and turbcharger as possible so it can be coverted into work energy.

By the same token, I also want to lower heat rejection as much as possible, and then deal with the rejected heat as efficiently as possible.

What rejected heat there is, is distributed to the water and oil cooling systems. My question is, then, has to be: which is more effective, 1), a smooth coated surface that enhances the speed of heated oil return to the pan and the rest of the oil cooling system but lessens the effectiveness of of the engine block as a radiator, or 2), or slowing the rate of return slightly but increasing the radiation potential of the block surface?

As this is a wet-sump motor, I'm not going to paint or coat the crankcase internally, and yes, I've got many, many hours detailing, enlarging, smoothing, contouring, and gasket-matching the oil and water systems inside the block and outside on the various appurtenances.

I am DEFINITELY going with an oil-shedding coating on the rods and crank throws (along with a windage tray).

Sheesh--I almost made sense :shock: Do I get a cookie?

Eddie":2sc5qtef said:
Even Websters, 1913, lists this as obsolete, compared to "appertinances". :roll:

What happens when the oil shedding coating starts to fail? Does it flake off, or wear like soft alloy, or go in little gritty bits? I would be wary of these things unless you had an aircraft-like maintenance/inspection schedule.

Good questions, and they need to be asked. I'll find out in a day or so, when next I have time for a field trip over to Polydyn.

addo":1hd6vm11 said:
Eddie":1hd6vm11 said:
Even Websters, 1913, lists this as obsolete, compared to "appertinances". :roll:

The only Webster I've got here at home (c. 1961) lists Eddie's spelling and does not indicate it as archaic or obsolete. It does not even list your spelling, nor AFAIK have I ever seen your version in print. Perhaps this is in the same vein as "Aluminum" vs. "Aluminium?" Your lot does spell things a bit differentlyfrom the way we do.

1 : an incidental right (as a right-of-way) attached to a principal property right and passing in possession with it
2 : a subordinate part or adjunct <the appurtenance of welcome is fashion and ceremony -- Shakespeare>
3 plural : accessory objects : APPARATUS



No dice!!!


And for comparison:
http://www.urbandictionary.com/define.p ... +my+nizzle
(Don't click if you can be offended in any way shape or form)

:oops: Hmm... I truly can't find my original source at this moment!

Two strikes against me!
http://machaut.uchicago.edu/cgi-bin/WEB ... purtenance

The Macquarie Concise Dictionary:
// noun 1. something accessory to another and more important thing; an adjunct. 2. Law a right, privilege, or improvement belonging to and passing with a principal property. [Middle English, from Anglo-French, from Latin: belong to]

I've been wrong twice this week. Shocking.
StrangeRanger":27fnxcaq said:
Grumpy Jenkins used to paint the insides of his engines black to absorb heat and the outsides white to radiate it.

To dredge up an old issue... Actually flat black is the king of emissivity. That's why the SR-71 is painted the color it is.

As for internal painting... I think I'd be wasting my time coating the inside of the crankcase of a street motor, but I might be inclined to coat the water jackets. When I got ahold of my current truck, the radiator was trashed with sediment fouling, the core plugs were leaking, there was an inch of 'gravel' in the bottom of the block, and the water passages between the block and head were partially occluded with rust build-up.

As the 300 is a thinwall casting, it bothers me that any dimensional margin of safety has spalled off and is lurking in the cooling system...
...another true gearhead with ecletic tastes who thinks for hisself:) I likes it!

I'm grateful for all the input; I am trying to incorporate all the "newish" pieces, knowledge, and processes I can, and trying to explore and learn about them all.

That bit on your site about installing mushroom lifters in a non-mushroom engine was interesting, VERY interesting. With the advent of OEM hydraulic roller lifters, mushroom lifters got sorta bypassed on most American engines designed in the period between the end of WWII and the '80's.