Engine v Muffler Blackout

[Alan D.]

Multiple posts on muffler blackout and same on engine compartment blackout exist.

Are these the SAME? The simple answer is NO! (At least that’s my opinion today)

Questions, especially from newer members, continue to be asked along with a possible misunderstanding.


Example of blackout paint can be found in the engine compartment, underside of hood, and inner fenders.
Many C2’s still have that original blackout paint today, it’s paint and lasts a long time.
It’s a flattened "eggshell" sheen black lacquer, which was sprayed in the Paint Shop just prior to the final bake oven.


While chassis blackout (seen on mufflers) was GM #3686683 "Underbody Protective Coating", described as a diluted asphalt mastic applied by an airless-sprayed with a pneumatic Johnstone pump from 55-gallon drums. It was quite thin, nothing like actual undercoating, closer to diluted asphalt by mineral spirits.

We have blackout paint and chassis blackout

I would like to see more specificity on the subject in our posts.

So let the comments fly, appreciate your thoughts. (Most of the above is from elder members)

Alan

[Mark E.]

"We have blackout paint and chassis blackout."

Are you representing a business that sells this?

[Mark F.]

Multiple posts on muffler blackout and same on engine compartment blackout exist.
Are these the SAME? The simple answer is NO! (At least that’s my opinion today)...Questions, especially from newer members, continue to be asked along with a possible misunderstanding. I would like to see more specificity on the subject in our posts.
So let the comments fly, appreciate your thoughts.(Most of the above is from elder members) ...Alan

Hi Alan,

Adding to your thoughts, here's what I dug up per John Hinckley...
Per John Hinckley's article "The Color Comes Through" on pages 36-40 in the October '06 issue of Corvette Enthusiast, here are the words he uses:

“INITIAL BAKE: The body was oven-baked for 30 minutes at 140° F. Small interior and exterior parts are placed on the floor and painted. Undercoat material was sprayed in the wheel wells, and "blackout" was sprayed on the underside of the hood, in the engine compartment and the wheel wells, with flattened black lacquer.”

Per John Hinckley's C2 Assembly Process Presentation (available in the Database of Restoration Documents [DoRD] Sticky Post), here's what he says:

“Spray chassis blackout paint on the outboard side of both mufflers.”
PS - This was the last Chassis station before Body Drop

And here’s how he described the material used at Dow-Smith:

“A.O. Smith installed the cowl-mounted female hood latches and the cross-cable AFTER the Paint Shop, so those items didn’t show any engine compartment blackout overspray like they usually did on St. Louis bodies.”

[Tony S.]

Multiple posts on muffler blackout and same on engine compartment blackout exist.

Are these the SAME? The simple answer is NO! (At least that’s my opinion today)

Questions, especially from newer members, continue to be asked along with a possible misunderstanding.


Example of blackout paint can be found in the engine compartment, underside of hood, and inner fenders.
Many C2’s still have that original blackout paint today, it’s paint and lasts a long time.
It’s a flattened "eggshell" sheen black lacquer, which was sprayed in the Paint Shop just prior to the final bake oven.


While chassis blackout (seen on mufflers) was GM #3686683 "Underbody Protective Coating", described as a diluted asphalt mastic applied by an airless-sprayed with a pneumatic Johnstone pump from 55-gallon drums. It was quite thin, nothing like actual undercoating, closer to diluted asphalt by mineral spirits.

We have blackout paint and chassis blackout

I would like to see more specificity on the subject in our posts.

So let the comments fly, appreciate your thoughts. (Most of the above is from elder members)

Alan

Alan, here are a couple factory photos. These photos have been published before. The color photo is from the 1965 production line. You can clearly see where blackout was applied to the top of the exhaust pipes beginning just below the bottom of the driver's side exhaust manifold. Scott Smith had a 1965 big tank car at the St. Charles National Convention in 2008 that had evidence of this level of blackout being applied to the top of the exhaust pipes. So exhaust blackout is not limited to only the mufflers. As a 1965 Chassis judge, I would consider this level of exhaust system blackout typical for the 1965 production year. A number of years ago, Rick Jones from the NM chapter had a factory pair of exhaust pipes taken from an original 1964 car that had been stored in an attic. He had them at the Lone Star Regional. The blackout was so heavy on the entire pipes, that the blackout was very evidence decades later.

The second photo is from the 1966 production year. It shows the typical appearance of blackout on the outboard side of the muffler. Again, I would consider this blackout, including runs, TYPICAL factory production.

John Hinkley's comments are always helpful, but not all-inclusive since we have original cars that exhibit features that also help tell the story about how these cars were built and finished. The stories continue to be uncovered. There is still more to learn. If you were there at the line first-hand one month, there may have been assembly differences months later in the same model year, so a one-size-fits-all explanation is not always accurate. That's where the fun is: being an archaeologist and findings these manufacturing nuances. Fun stuff!

I hope this helps.
Tony

[Jack M.]

In addition to Tony's photos, don't forget that Noland's book has many undercarriage images.
And this photo is from a 64 fuelie... published in the Sept 1964 issue of Motor Trend.

Motor Trend - Sept 1964.jpg

[Jack M.]

Not all Corvette muffler blackout was consistently sprayed... even with sequential vehicles.
This image is a 1966 Convertible... it was directly in front of the 1966 Coupe muffler, that Tony posted.
(both images were taken on 9-28-65)

1966-Corvette-Body-Drop-(9-28-65) - Convertible.jpg

[Mark E.]

In addition to Tony's photos, don't forget that Noland's book has many undercarriage images.
And this photo is from a 64 fuelie... published in the Sept 1964 issue of Motor Trend.

Motor Trend - Sept 1964.jpg

Poor resolution but this looks like it was driven hard in its young life... scrapes on the mufflers and exhaust, exhaust pipes and spring are several shades of gray (rust? dirt? fluid leak?). TA hardware and shocks look dirty. Not surprising for a road test car, I suppose.

Still wondering if OP is trying to sell paint.

[Alan D.]

So the responses show my confusion on "We have blackout paint and chassis blackout"
Both of these are usually called blackout even by John Hinckley
So are these different? I'm suggesting they are.
The blackout paint still exists today in the engine compartment & on underside of hoods. While the chassis blackout in aged cars is pretty much gone, however some small evidence can still be detected.
Oh NO Selling Mark!!!!

[Jack M.]

Poor resolution ...

My apologies... would you like a refund?

... scrapes on the mufflers and exhaust ...

Ummm, I don't think so... where is the surrounding damage (especially on the fiberglass)?
We've been told that blackout paint was extremely thin in consistency, and prone to runs...
After a year of testing, perhaps just heavier coverage areas (including runs), still remained.
(and back in the 60s, I doubt the fleet vehicles had their chassis detailed very often)

Kindly show us some of your chassis blackout research images...
Perhaps you have one where the worker is using that infamous 'mitt'. LOL

[Frederick H.]

Alan, what blackout product are you using/suggesting for chassis? I am replacing the rear portion of my exhaust system and would like to apply it prior to install.
Thanks.

[Alan D.]

Frederick,
I have not found a preferred method to use for chassis blackout yet, my next attempt will be to use undercoating in a can and spray some thinner over that, hopefully causing some more runs.
As mentioned "chassis blackout (seen on mufflers) was GM #3686683 "Underbody Protective Coating", described as a diluted asphalt mastic applied by an airless-sprayed with a pneumatic Johnstone pump from 55-gallon drums. It was quite thin, nothing like actual undercoating, closer to diluted asphalt by mineral spirits."

[Alan D.]

Fred,
Just left a friend's body shop and we discussed "The WURTH Multi Sprayer Application Gun – 891111 can spray SKS Stoneguard, Body Wax / Rust proofing, Underbody Seal or any petroleum or water based product This allows thicker than normal products to be sprayed at low pressures with the advantage of very little over spray. ." (from Wurth literature)

Would like to try that with thinned petroleum stuff however the cost of the gun ($300) is more than I want to experiment with.
Alan