Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

[Larry E.]

Most of us know about the above. Picture Below. I have this on my 66 Coupe (Made Sept. of 65) car.
Has anybody ever researched (Current Thinking)this to see what are the dates of seeing this from Start To Finish?
Perhaps my marking is not what is seems to be?? Thanks>Larry

[Mark F.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

Most of us know about the above. Picture Below. I have this on my 66 Coupe (Made Sept. of 65) car. Has anybody ever researched (Current Thinking)this to see what are the dates of seeing this from Start To Finish?
Perhaps my marking is not what is seems to be?? Thanks>Larry

Larry,

If you're only talking about C2s (dunno if '68s and beyond had dimples or not?), my car was built and shipped on June 28, 1967 (K28) and it has the dimple.

My Vin derivative is 21971, so there were 969 cars after mine.

Last time I heard, Rick Hendrick owns 22940 - dunno if his is dimpled or not.

[Don H.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

I call it a pimple (raised), rather than a dimple (inset). Refer back to this thread for in depth discussion a few years ago.. The question of when they started and when they ended remains unanswered.
https://www.forums.ncrs.org/showthre...quot&highlight

[Tim G.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

I used to know the approximate dates of possible "pimple delete cars" but I've forgotten. I'm sure those with sharper memories than me can fill in the blanks. I'd like to know so I can forget that data again.

[Larry E.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

Also one wonders if the "pimple" was consistent for Coupes Vs. Convertibles. Like I
said before my very very early 66 Coupe has it but my very very late 66 Convertible
does not. ??? Thanks>Larry

[Patrick B.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

My March 67 St. Louis convertible has it. Since the front surround panel is the same for convertibles and coupes, both should have it. However, if different molds were used for St Louis and AO Smith bodies, that may cause differences. Also since most have these cars have been repainted, some painters probably thought the dimples were flaws that should be sanded off with little effort.

[Keith B.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

I thought I read by John Hinckley that there was only one supplier for panels for both plants.

[Mark F.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

My March 67 St. Louis convertible has it. Since the front surround panel is the same for convertibles and coupes, both should have it. However, if different molds were used for St Louis and AO Smith bodies, that may cause differences. Also since most have these cars have been repainted, some painters probably thought the dimples were flaws that should be sanded off with little effort.

Hi Patrick,

This shot is from Michael Garver's post #13 in the following link:
https://www.forums.ncrs.org/showthre...quot&highlight

In the caption at the top of the image, John states there was only one mold...
To my eye, the pimple would have been created somewhere near the blue circled area...the part is formed upside down, so the side facing us is the passenger side and they're pouring the resin on the headlight bucket end.

So apparently, the male part of the pimple was in the upper half of the die (above their heads) and the corresponding female indentation was apparently in the die laying on the press bed.
MFG Ashtabula_001.jpg

[Mark F.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

I thought I read by John Hinckley that there was only one supplier for panels for both plants.

Keith, yes - see post #8

[Kenneth B.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

Hi Patrick,

This shot is from Michael Garver's post #13 in the following link:
https://www.forums.ncrs.org/showthre...quot&highlight

"Below is some information from John Hinckley - rescued from the other forum. The process would suggest that the depression that caused “Pappy” was part of this fixture and therefore the protrusion was formed in the mold on every panel, part of every car - no exceptions."

In the caption at the top of the image, John states there was only one mold...
To my eye, the pimple would have been created somewhere near the blue circled area...the part is formed upside down, so the side facing us is the passenger side and they're pouring the resin on the headlight bucket end.

So apparently, the male part of the pimple was in the upper half of the die (above their heads) and the corresponding female indentation was apparently in the die laying on the press bed.
[ATTACH=CONFIG]120581[/ATTACH]

There is No male dimple. There would be a round indentation in the half of the mold that made the top of the surround that would make the raised bump on the fiberglass. God knows why its there.

[Owen L.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

Also one wonders if the "pimple" was consistent for Coupes Vs. Convertibles. Like I
said before my very very early 66 Coupe has it but my very very late 66 Convertible
does not. ??? Thanks>Larry

My May '67 St. Louis coupe has it.

[Mark F.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

There is No male dimple. There would be a round indentation in the half of the mold that made the top of the surround that would make the raised bump on the fiberglass. God knows why its there.

Hi Kenneth,

If the pimple was made on purpose (and as you say, who knows why ?), the image below represents how the two halves would be made by the die maker. Similar concept to a stamping plant die set - even though this is more of "press-forming" process. I think I remember you saying you had worked in a foundry(?), so this is nothing new for you...

Normally, if there's no male dimple (or defect in the die ?), there's nothing up there to squeeze the fiberglass into the female void.

But I suppose if the female dimple (defect ?) is there and there's no corresponding male dimple, the fiberglass might have SAGGED into the void under the pressure and heat used to complete the part.

Had this been 40+ years ago, I could have asked Earl (the guy in the office next to me) who was PPG's tech services rep for the Ashtabula MFG plant. And the burning questions and mysteries go on and on and on...

Pimple Dies.jpg

[Owen L.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

Normally, if there's no male dimple (or defect in the die ?), there's nothing up there to squeeze the fiberglass into the female void.

But I suppose if the female dimple (defect ?) is there and there's no corresponding male dimple, the fiberglass might have SAGGED into the void under the pressure and heat used to complete the part.

If it's a male projection, the underside should have a matching "hole"... I've never looked underneath, so don't know if it's there or not.

I think it's a flaw in the mold and was the result of the resin pooling in a divot. That Chevrolet didn't catch and fix it early on is par for the course considering they let the waaaaay more obvious valve cover flaw go on for years.

[Patrick B.]

[Kenneth B.]

Re: Question On The Infamous "Paint Dimple" On The C2 Firewall Side Facade

MARIK
I owned a Pattern shop that made the tooling for foundries & permeant mold shops. For the sand foundries the tooling Is the male version to make the negative sand mold to pour the metal into. Permeant molds are the female tooling to pour the metal or liquid plastic in. There is pressure.to inject Aluminum or plastic so you dont need any pressure from the upper half to squeeze into recesses.