Engine coating opinions?

[loopie]

I am in the process of restoring my 69 S. It will never be original but I want it to be close. During restoration of the engine I am having some of the parts coated in various ways. The company that is doing the coatings has been around a long time and they know what they are doing. All the coatings are internal except for one which will be obvious to anyone inspecting the car. It is a thermal dispersant that would be applied to the outside of the heads. It will not only disperse head faster but it will help shed dirt which may help keep the fins from getting blocked.

What will make this obvious is it will make the heads black. This car will not be 100% original, more like 95% original. Would the heads being black adversly affect the value of the car?

TIA for your opinions.

[911pcars]

IMHO, the increased heat dissipation is minimal, and while internal coatings have their place, external coatings won't prevent oil from attracting dirt and rat nests from the area, so no advantage there.

As for resale value, no unless a concours judge crawls underneath to look at the heads and removes points. Do they go that far? If so, that whole scene is amusing.

Sherwood

[304065]

Don't coat the heads. The fan blows 1300 liters of air per second at high speed over them, nothing is going to keep them clean. As far as thermal coatings, it's not the F-117A, save your money.

If I looked at a car with such an obvious standout I would wonder what else was "different" and would adjust my valuation accordingly.

[Flätsix]

Don't coat the heads. The fan blows 1300 liters of air per second at high speed over them, nothing is going to keep them clean. As far as thermal coatings, it's not the F-117A, save your money.

If I looked at a car with such an obvious standout I would wonder what else was "different" and would adjust my valuation accordingly.

The engine consumes 33-240 liters of air per second... so I think you off a smidge. Where are you getting this info from?


Please tell me I missing something or my humor degauser is off.
IMHO I wouldn't call this an obvious standout. Design 90 wheels would be an obvious standout. So out of curiosity, what would this flagrant blasphemy devalue the car?

[tfiv]

I think a fresh, properly detailed (plating of hardware etc.) Porsche engine is a gorgeous piece of machinery, not in need of any sort of embellishment.

[ErVikingo]

There are some reported minimal gains with coatings on the inside so why not.

As to the exterior of the heads; I can't see how you'd gain on heat radiation properties by adding a coating except if its going to keep them clean and thus maintain more surface area directly exposed to the air flow. Anyhow, I think it would be overkill on this application.

Then again, perhaps one with knowledge in metallurgy and thermal radiation properties could measure the difference in radiation properties between coated vs. exposed metal.

We don't even run that on engines which operate at 7500 to 8000 rpms most of the time.

By the way Flatsix, John is referring to air moved by the fan and not consumed by the engine. Careful or he'll crack out his fan tip speed graph (in percentage of speed of sound - ).

John, loved your graph and spent some time discussing it today with my mechanic.

[pu911rsr]

You can modify the emissivity of a metal with a coating, I doubt it makes any appreciable difference in head temps.
Phil

[Flätsix]

[QUOTE=ErVikingo]Th
By the way Flatsix, John is referring to air moved by the fan and not consumed by the engine. Careful or he'll crack out his fan tip speed graph (in percentage of speed of sound - ).
QUOTE]

I know, that's why I'm asking.

Loopie

Coat the heads, get the whole Swaintech treatment, valves and everything.

[304065]

Attached is a scan of the factory fan flow for the 911T, 911 Normal and the 911S, up to the 1968 Model year, as the spec book dates from December, 1967.

As you can see, the fan cooling airflow is around 1390 liters per second for the '67S. I would expect it to be very close to that for a 69 2,0 liter.

[loopie]

Thanks much for all the great feedback!