69 muffler black-out question & shim markings

[Greg L.]

I'm pretty sure that now is the time for the black-out procedure but just wanted to check with you all before I do something stupid. Have a look at my pic and see if it looks ready. I don't think the wheels should be on so that is why they are still off.

For the actual procedure it was just one or two quick passes to cover the outboard side and the bottom of the mufflers and nothing was masked, correct? Also was the black-out pretty much flat or a semi gloss like under the hood? I would lend to think that they would both be the same but I think the body black-out and chassis black-out were done separately so I'm not quite sure about this.

For the shim markings should they be actual numbers or slashes? This is a late Jan 69 car.

Thanks.

[Chuck S.]

Re: 69 muffler black-out question & shim markings

I'm pretty sure that now is the time for the black-out procedure but just wanted to check with you all before I do something stupid. Have a look at my pic and see if it looks ready. I don't think the wheels should be on so that is why they are still off.

For the actual procedure it was just one or two quick passes to cover the outboard side and the bottom of the mufflers and nothing was masked, correct? Also was the black-out pretty much flat or a semi gloss like under the hood? I would lend to think that they would both be the same but I think the body black-out and chassis black-out were done separately so I'm not quite sure about this.

For the shim markings should they be actual numbers or slashes? This is a late Jan 69 car.

Thanks.

Not semi-gloss, not even satin...if not flat, then semi-flat. Your description of the spray technique sounds about right, but don't work so hard at this it doesn't look, well...spontaneous.

Tripoli shows arabic numerals for a 69. Once again, draw them crudely but smoothly and spontaneously...like a guy with a sixth grade education that draws numbers all day in a hurry.

[Lyndon S.]

Re: 69 muffler black-out question & shim markings

Did you spray paint the gas tank? It looks like dull aluminum spray paint on the tank, could just be the photo?

[Alan S.]

Re: 69 muffler black-out question & shim markings

Hi Greg,
I thought that the body was on when the black out was done so that a little black got on the underbody too. I remember some black on the side of the battery compartment and the jack compartment. The frame acted almost like a mask in limiting where there was black and where there wasn't any on the fiberglass. Is this recollection a dream?
Regards,
Alan

[Chuck S.]

Re: 69 muffler black-out question & shim markings

...I thought that the body was on when the black out was done so that a little black got on the underbody too. I remember some black on the side of the battery compartment and the jack compartment. The frame acted almost like a mask in limiting where there was black and where there wasn't any on the fiberglass. Is this recollection a dream?...

Alan, I think you are probably right in that the muffler blackout was done after body drop, but I'll defer to those that know.

In any event, I don't think this will have a material difference on the appearance of the muffler blackout. IMO, the gun used for this operation would have needed to be a narrow fan gun to avoid getting blackout everywhere it wasn't wanted. Most of the comment that I remember has to do with minor blackout overspray on the spare tub, which is immediately adjacent to the mufflers.

As for the battery and storage compartments, I couldn't make out any blackout overspray, because the bottoms of the compartments, and most of the sides were already fully black from application of undercoating...the characteristic "wave pattern" of the undercoat application was unmistakeable.

To my knowledge, this undercoating application isn't shown in the AIM, and I can't explain what I've observed. It was also applied in the differential tunnel on my car...in those areas, I would suspect it was intended as sound deadening to reduce noise levels in the passenger compartment, but I'm guessing.

[Robert C.]

Re: 69 muffler black-out question & shim markings

Ok guys, you aren't going to like this but ,according to the "original pipes" and blacked- out mufflers on my 71 the black goo (fairly flat and thick)was splashed on by hand mit with the mufflers and rear pipes off the car and upside down so that the black actually runs down the sides of the muffler toward the top! Most restored cars have a nice clean black muffler bottom, sprayed on. I'm not sure they did it that way in 69', but I bet it was.

[Greg L.]

Re: 69 muffler black-out question & shim markings

Ah Lyndon you got me...the tank was sprayed with Eastwood's "Tank Tone. I couldn't justify replacing a perfectly good AND date coded tank just for the sake of any pre body drop chassis pics. I'm not at all pleased with the "tank tone" and there is no way I'd ever use it on a car where you can see the tank like on a "A" or "F" body.

I think I found my answer just by accident today. If anyone has a copy of Rick Bizzoco's "1969 Stingray Guidebook" check out page 10 because it shows a 69 coupe just before body drop and the mufflers are surely black. You can also see that the black-out in the wheel wells only covers the sides of the battery and jack compartments and not the rears of them.

I can't see any shim markings in the photo so are there any other comments on what the shim markings should look like. I thought this was about the time that they went from slashes to numbers or vice versa...

[Chuck S.]

Re: 69 muffler black-out question & shim markings

Ok guys, you aren't going to like this but ,according to the "original pipes" and blacked- out mufflers on my 71 the black goo (fairly flat and thick)was splashed on by hand mit with the mufflers and rear pipes off the car and upside down so that the black actually runs down the sides of the muffler toward the top! Most restored cars have a nice clean black muffler bottom, sprayed on. I'm not sure they did it that way in 69', but I bet it was.

Bob, you probably missed the multiple times John Hinckley has debunked the "mitting" theory. I think there are others that are still firmly committed to the mitting theory. I suppose observations don't lie..the problems come in the interpretation of the observations and what is typical production.

However, extra wet coats, or overspraying, would also create runs with thin paint. Like the TIM&JG's description of runs in the frame paint, I would expect all exhaust systems didn't have them.

I do seem to remember the "upside down" runs being mentioned before, so it's possible the chassis were blacked out before body drop. I also seem to remember some discussion about whether the "upside down" runs were on service replacement parts, or production exhaust systems, or both. I can't remember how or if the discussion was resolved...I suspect it was not.

[Greg L.]

Re: 69 muffler black-out question & shim markings

Okay Robert, I'll buy that to a point. I don't know about the "mitting" because original tire tubs are known to have black-out overspray on them. I can however see that that the mufflers were sprayed with black-out when the chassis was still upside down. This would account for the overspray on the tire tubs and the "upward" paint runs.

[Chuck S.]

Re: 69 muffler black-out question & shim markings

...I think I found my answer just by accident today. If anyone has a copy of Rick Bizzoco's "1969 Stingray Guidebook" check out page 10 because it shows a 69 coupe just before body drop and the mufflers are surely black. You can also see that the black-out in the wheel wells only covers the sides of the battery and jack compartments and not the rears of them...

Gregster, you are going to make a restorer yet (if you give up on shortcuts like "Tank Tone").
You started out by asking a question, then ended up by answering it yourself.

Technically speaking, the material the gas tank is made out of appears to be galvanized sheet...the cut edges where the steel is exposed by stamping rust big time! There is NO PAINT that will duplicate that finish.

[Robert E.]

Re: 69 muffler black-out question & shim markings

Greg,

This image was taken from a 1971 6,000 mile multi Top Flight award winner at the 2004 Nationals in Windsor.

Robert

[Michael H.]

Re: 69 muffler black-out question & shim markings

Okay Robert, I'll buy that to a point. I don't know about the "mitting" because original tire tubs are known to have black-out overspray on them. I can however see that that the mufflers were sprayed with black-out when the chassis was still upside down. This would account for the overspray on the tire tubs and the "upward" paint runs.

There was a point in production where the the chassis blackout process, including mufflers, ended entirely. I'm not exactly sure when that occured though but my guess in late 60's?
From that point forward, it's likely that mufflers were coated off line with chassis black. (and eventually with flat black paint)

The only location on the entire chassis line that ever had an enclosed station for blackout was just before body drop. That was at the end of the line of chassis that were right side up. Blackout was the last thing done before the body was installed. If the mufflers were installed before blackout, there would also have been chassis black on the spare tire carrier, which is likely the case for early C3's?

If some original C3 mufflers show runs running up instead of down, I would have to guess that these were coated off line. In that case, there wouldn't be any overspray of chassis black on the tire carrier.

It's possible that the muffler assemblies were painted flat black at the source and arrived at the Corvette plant already painted in the 70's.

[Chuck S.]

Re: 69 muffler black-out question & shim markings

...This image was taken from a 1971 6,000 mile multi Top Flight award winner at the 2004 Nationals in Windsor...

Thanks for the pic, Robert...What I see is there are no runs at all; just a simple dry overspray break line.

Of greater interest to me is something I've never noticed before on 68-72 Corvettes...the rear wheel opening BLACKED OUT on the very bottom to conceal the flange at the bottom of the wheel opening.

Anyone know if this is black out characteristic is typical of 70-72? Unique to 71 and later only?

[Patrick H.]

Re: 69 muffler black-out question & shim markings

Thanks for the pic, Robert...What I see is there are no runs at all; just a simple dry overspray break line.

Of greater interest to me is something I've never noticed before on 68-72 Corvettes...the rear wheel opening BLACKED OUT on the very bottom to conceal the flange at the bottom of the wheel opening.

Anyone know if this is black out characteristic is typical of 70-72? Unique to 71 and later only?

Chuck,

1. I think that is a shadow on the lip of the wheelwell.
2. That exhaust is not original to the car. It has been replaced, even with only 6000 miles.

See mine below. Just as inaccurate, so to speak, as I did it myself.

Patrick

[Joe L.]

Re: 69 muffler black-out question & shim markings

All 1969, 1970 L-46 and 70-72 base engine GM SERVICE mufflers, when they were available, were always painted semi-flat black on the bottom surface. These were the 2" mufflers used only for all 1969, 70 L-46 and 70-72 base engine. I purchased many of these in the "old days". Some 1963-72 2-1/2" SERVICE mufflers were also painted semi-flat black on the bottom surface.

Of course, it's possible that this was done only for SERVICE. Nevertheless, it implies that it's very possible they were painted from the supplier in PRODUCTION, too.