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PostPosted: Sun Jan 06, 2019 3:44 pm 
356 Fan

Joined: Wed Mar 26, 2008 12:06 pm
Posts: 1020
Location: Orinda, CA
The vast majority of the heat transfer from the heads is due to forced convection to the fan cooling air, this is what the deep finning of the heads is for. Radiation and conduction are very minor effects. The blackening was probably to increase the emissivity of the head surfaces which would slightly increase the radiation heart transfer. But in actuality a deeply finned surface, irrespective of the surface finish, has an effective emissivity which is very high due to the multiple reflections between the fins. So bottom line is the blackening of the heads probably had near zero effect on head temperatures. But it does look kind of neat!


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PostPosted: Sun Jan 06, 2019 4:36 pm 
356 Fan
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Joined: Sun Jun 19, 2011 9:47 am
Posts: 547
Location: Rochester, NY
Good radiation absorbers are usually good emitters. This might be true for heat dissipation with a black coating as long as it is also 'black' at IR wavelengths. Ordinary black paint isn't necessarily a good heat emitter since paint pigments are designed for visible wavelengths. Interestingly, common black anodizing becomes less absorbing at IR wavelengths, differing very little from raw aluminum. There is broad spectrum black anodizing that would work best, though I'm not sure how long its been around. Bottom line I agree with Alan, black heads do look cool.

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Bruce

'60 356B (Ivory cab)
'63 356B (Ruby Red coupe)
'67 912 (Rally car)
'68 912 (Golden Green)
'70 911T (Bahia Red)
'14 911-50th (GTS)
'18 Beck 550 Spyder (356C motor)
'62 Austin Mini (850 stock)


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PostPosted: Sun Jan 06, 2019 4:53 pm 
356 Fan
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Joined: Thu Jul 03, 2008 7:25 pm
Posts: 114
Location: San Diego, California
The Maestro wrote :

The Differences between Normal Heads and C/SC/912.

Early 356A Normal heads had a circular Intake Port. 356A Supers got the
oval-shaped port. Both 356A N/S Heads have Brass Intake Seats that should be
replaced with steel seats. 356A Heads Date Stamped around 12-14/59 (March,
1959) may have a Common Mode problem with EXHAUST valve recession too. Avoid
them.
All 356B Heads have Steel inserts for all the valve seats. Normals and
Supers in the 356B series have similar-sized oval-shaped Intake Ports, while
Super-90's have the biggest Intake Ports- the same size as the Intake Ports
of C/SC and 912 Heads.

By 1962, the Normal and Super heads were virtually identical and pretty
good. These heads can be ascertained by the presence of two triangular
casting bosses cast into the push rod return hole side of the head. With
some clever Porting the Intake Ports of the Normal/Super Head to C/SC/912
specs can allow use of Webers, Solexes or "C" Zenith intake manifolds.
Since the 356A/B Normal/Super Heads have a 22.5 degree Conical cut in the
Combustion Chamber and most EVERY Piston made today wants to see 30 Degrees,
we do the 30 Degree Conical cut on most every A/B Head.
356A/B Normal Super Heads take NON-Sodium filled exhaust valves (Ate 3030
Intakes, Ate 3043 Exhausts).
The Super-90 has the Largest Intake Valve in the Pushrod series using
the Rare and getting Rarer Ate 3041 Intake, but had the same Ate 3043
exhaust valve as the 356A/B Normal/Super.
C/SC Heads:
"Real" SC Heads (and some early 1964 "C" Heads), like ALL Super-90 Heads-
were anodized "black" and then machined (so the "blackening" is on all the
unmachined areas). The "blackening" raises the Emissivity from about 0.1 for
Aluminum to near 0.9. This increases the Radiative Heat Transfer
significantly, and although most heat transfer is from Conduction & Forced
Convection, Radiative Heat Transfer can be significant at high temperatures,
such as when Racing or driving across Death Valley.
However, the anodizing (or the R&D for the 911) must have been too
expensive because the later 1965 SC's went back to "regular" Aluminum (no
Black anodizing), suspiciously about the time of the first 912.
Both the C and SC Heads take the same Intake Valve (Ate 3044), but the SC
(and 912) uses the Sodium-Filled Ate 3048 Exhaust. (The "C" got stuck with
the solid, non-Sodium Ate 3045 exhaust, but can take the Sodium-filled Ate
3048).


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PostPosted: Sun Jan 06, 2019 5:38 pm 
356 Fan
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Joined: Tue Apr 15, 2008 4:37 pm
Posts: 4053
Location: SW Los Angeles
Thanks, Guys: I've been educated.

Mike

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Lomita, CA
'63 B coupe


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PostPosted: Tue Jan 08, 2019 12:01 am 
356 Fan

Joined: Sat Sep 20, 2008 10:25 pm
Posts: 39
Maybe this was done to differentiate the S90 from lesser components during the assembly process on the line?

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PostPosted: Tue Jan 08, 2019 12:26 am 
356 Fan
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Joined: Tue Apr 15, 2008 4:37 pm
Posts: 4053
Location: SW Los Angeles
Maybe, Don, as there is a difference in valve adjustments.

Mike

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Lomita, CA
'63 B coupe


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PostPosted: Tue Jan 08, 2019 6:40 pm 
356 Fan
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Joined: Fri May 09, 2008 9:36 pm
Posts: 392
For hot rodding Corvair engines the hot tip was to get a bottle of "Stove Black" made for wood stoves. I may still have a bottle of it around somewhere.

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