Well if you assume a blacktop road with an Er value that's equal to the Ed for the black diff cover then since Tr=Td=250 F the diff cover picks up as much radiant heat from the road as it radiates away to the road and Rn=0 because... Rn={(5.018x10^-10)(Ed)}{(Td+459.67)^4-(Tr+459.67)^4} Watts/ft^2.

As can be seen below from the pic of my diff cover only a fairly small area of it actually faces the road and the rest sees the ambient air...



...and for Td=250 F and Ta=110 F the diff cover radiates a net to the air given by... Rn={(5.018x10^-10)(Ed)}{(Td+459.67)^4-(Ta+459.67)^4}={(5.018x10^-10)(0.91)}{(250+459.67)^4-(110+459.67)^4}={(5.018x10^-10)(0.91)}{(709.67)^4-(569.67)^4}=67.7 Watts/ft^2. Then you need to multiply this by the ft^2 area facing the air.

If the road surface was really 250 F I'd just hang out in my airconditioned RV until a cooler day so I wouldn'r damage 12 very expensive tires. I shoot tread temperatures for each tire every time I stop for a leak because that's a good way of monitoring for low tire pressure and the highest I've seen is about 150 F.

 

If you have a Fastenal near by, they have SS 5/16" x 1 1/4" hex head for around $.50 each. At least that't what I paid for them here.

http://www.fastenal.com/web/location...on=selectStore


http://www.fastenal.com/web/location...damon&state=TX

 

Thanks, Mike. There's one in my town! I might have to run up there and get 12 and pull mine out one at a time and hope I don't create a leak...

 

I'll be painting mine black, as function is more important to me than appearance.

That IS why you put the finned one on, isn't it? To get rid of heat?

Pop

 

I just prefer the aluminum look. Mine won't be black. I put it on partially for better cooling, and partially for looks.

 

Just finished my '08 Rear Diff cover last night on my '02. Thanks for the post. Thanks SuperDoodie for the bolt sizes, I work at a power plant and we had exactly what you specified. Thanks beanheadD5 for the sandblasting idea. I blasted it then coated it with Dupli-Color Engine Enamel w/ Ceramic. It says that it helps to dissipate heat which is what we want. It comes in a large variety of colors too.

When it comes to parts and lubes for my truck I try to stick with Ford. I bought the 75W-140 from Motorcraft at a ridiculous $24 a quart plus the additive. The only non-Ford thing I use is Chevron Delo 400 motor oil, oh and a K&N air filter. Thanks to all of the posters regarding the way to add the additive. I'll be doing that today to give the silicone time to cure.

 

oooohh, might want to look around a bit about the K&N. Apparently there is a lot of disdain for them on the 7.3 and stock air box. Something about how they seal.

 

Since it's inconvenient to pull the entire intake apart to inspect the compressor wheel for dusting on a frequent basis an easier way of monitoring the seal between the top of the air filter element and the lid of the air box is get a toothpaste size squeeze tube of petroleum jelly and apply a continuous bead around the perimeter of the top of the filter element and then seat the lid into this bead and secure the clamps. Then all you have to do is to occasionally lift the lid just enough to peek at the top of the filter element to see if any "tracks" have developed in the petroleum jelly seal!

I came up with this idea of using petroleum jelly in 1999 because my Banks stinger kit featured a drop in K&N element for my upgraded 99.5 air box and a tube of "K&N filter grease" was included along with directions for how to apply it and I think it's a great idea that everyone with a stock air box should employ no matter which drop in element they might choose to use!

Just Google... "K&N filter grease" ...and you'll get the whole story... "K&N Air Filter Facts You Should Know... Use K&N Air Filter Sealing Grease on the sealing surface that contacts the air box ...K&N sealing grease is compatible with all types of air filters, not just reusable K&N air filters, and all types of air boxes."

 

Interesting, Gene. I honestly did not believe you were correct on this, and did some research, and found out that you are absolutely correct. Basically, the black paint allows the heat to ESCAPE from inside to outside just as easily as it would allow the inside to warm up if the ambient temperatures were higher than the internal temperatures.

If anyone wants to do some reading behind the theory and principles involved, here is a link where it is explained fairly well and not too difficult to follow.
Zero Principle and optics

 

Thanks for all the info on the K&N air filter. I will definitely look into that.

I just added the fluid to the rear end and almost half the bottle of the additive to see how it performed. OMG, that stuff stinks. I put in 3.5 quarts of fluid. The manual calls for 6.9 pints. How do you know if it's full? I don't recall seeing in the earlier replies if the '08 cover holds more.

 

Joe, do you have a part number for this? When I pull it up on a Ford parts site it shows 3 applications.

 

See if this helps... Stamped on the cover is 8C34-4033-AA...

 

so painting the rear diff cover flat black = good
but
painting the intercooler pipes flat black = bad???

 

Well you can use my "real world" technique for getting it filled to its limit! My Mag HyTec had a dipstick so I keep adding fluid to the top of the line on the dipstick. Everything appeared to be fine running empty but after my first towing trip I'd vented some fluid and since the vent is located up high under the truck to avoid getting water into the diff it made a terrible mess under the truck!

 

The strategy is to paint an object black if it's surrounded by things that are cooler and to paint it white or better yet shiny silver if it's surrounded by things that are hotter.

The flat black turbo inlet boot should definitely be white or shiny silver so it doesn't absorb as much heat from the hotter engine components nearby.

The CAC tubes are a little more tricky because the air inside the CAC tube going from the turbo to the IC for example can vary from nearly ambient air temperature to 350 F during sustained operation at maximum boost. The parts of the CAC tubes that are near the exhaust manifolds should be white or silver but the parts of the CAC tubes that are near objects cooler than 350 F should be black!