65 double grove water pump pulley

[Keith B.]

the J/G states uniform gray color or black phosphate with a black rubber coating. what are people doing to refinish them?

[Gary B.]

Re: 65 double grove water pump pulley

Keith,

When I researched this question 3 years ago I learned the following. Some original pulleys were treated with Parkolac 30 which was a trade name for a liquid chemical that parts were dipped in post black phosphate and then baked in a 180-degree oven. I've never seen an original Parkolac-treated part, so I don't know what it looks like when new.

Gary

[Keith B.]

Re: 65 double grove water pump pulley

Anyone else?

[Patrick H.]

Re: 65 double grove water pump pulley

Gray (zinc) phosphate and black (manganese) phosphate are easy.

I read through Gary's threads here and on CF.
To mimic a rubberized coating, it may be possible to thin Plastidip, and then use that as a coating. Or, even the spray Plastidip.
The spray stuff comes out a bit irregular from the can but is often thin, so I'd lean towards thinning a can of it and dipping if you really had to have a rubber finish.

However, since the rubber version was an optional coating, and phosphating is easy, I'd just phosphate them if that's the finish you found when restoring the car.

Patrick

[Gary B.]

Re: 65 double grove water pump pulley

Patrick,

I don't think the Parkolac was a rubber-like coating. Richard Fortier is the person who tracked down some info for me about Parkolac and from his description it did not sound like a thick coating, nor a rubber-like coating. I would recommend the gray phosphate route, or perhaps semi-flat black spray paint. I don't know if most judges are deducting for such finishes. I suspect not.

Finally, I would wager that few judges know what Parkolac really looks like. I have no clue, other than I think it is not rubber-like.

Gary

[Patrick H.]

Re: 65 double grove water pump pulley

I'd like to see one that actually is done in Parkolac.
Frankly, it sounds more expensive and the odds of a supplier spending more money on a pulley finish...?

In later years the pulleys were optionally black phosphate, not gray.

[Gary B.]

Re: 65 double grove water pump pulley

Patrick,

I'd like to see one with the Parkolac coating, as well. I doubt I ever will.

I think you're correct about the black phosphate. I've seen black phosphate referred to as gray, by which i assume people mean very dark gray.

Gary

[Joe L.]

Re: 65 double grove water pump pulley

Patrick,

I don't think the Parkolac was a rubber-like coating. Richard Fortier is the person who tracked down some info for me about Parkolac and from his description it did not sound like a thick coating, nor a rubber-like coating. I would recommend the gray phosphate route, or perhaps semi-flat black spray paint. I don't know if most judges are deducting for such finishes. I suspect not.

Finally, I would wager that few judges know what Parkolac really looks like. I have no clue, other than I think it is not rubber-like.

Gary

Gary-------


Parkolac was not a rubberized coating, at all. It was more like a very thin coating like varnish or shellac. In fact, I think it got the last part of its name from shellac (I think the first part of the name was from the company that made it). I believe it was applied over a phosphate finish.

[Patrick H.]

Re: 65 double grove water pump pulley

If you do some more searching, Parkolac was used as a paint on firearms, and one source mentions steam engines and rail cars. There's an easily searchable photo or two of old semi-gloss to gloss black-painted bayonets and rifle parts reported to still be in original Parkolac.

[Gary B.]

Re: 65 double grove water pump pulley

Patrick,

That's very interesting. I would love it if I could just paint my pulley semi-gloss black and get no deduct. My guess is that is what is happening for the most part on the judging field already. It would be nice if the TIM&JGs gave some guidance about the similarity between Parkolac and semi-gloss black paint. I also like to know where the writers of the '65 JG text got the description of "black phosphate with a black rubber coating."

Gary

[Patrick H.]

Re: 65 double grove water pump pulley

Having been a part of several JG revision teams, there are moments when silly things get past all of us.
It depends how many people actually worked on that section, and how much old information was pulled from previous or other year JGs.

Don't assume that what's in the JG is correct, no matter how hard we tried to make it right.

[Keith B.]

Re: 65 double grove water pump pulley

Having been a part of several JG revision teams, there are moments when silly things get past all of us.
It depends how many people actually worked on that section, and how much old information was pulled from previous or other year JGs.

Don't assume that what's in the JG is correct, no matter how hard we tried to make it right.

That is part of question why I started this thread. the process described seem labor intensive and costly for a high production part like a pulley when all other pulleys I have seen where dipped painted. was hopping someone with a unrestored 65 would chime in.

[Edward D.]

Re: 65 double grove water pump pulley

I parkerize them. This is manganese phosphate which comes out very dark gray to black. Same process as used on firearms. Zinc phosphate is a lighter gray color. Parkerizing is simple to do but requires clean metal (sand or bead blasted) and you need to heat the manganese solution. You can get the chemicals or a complete kit online from multiple sources. "Parkolac", as I understand it, was a black lacquer dip coating, not very permanent. Any originals with this coating have likely rusted long ago. Your best bet for durability is to "parkerize" which is manganese phosphate. Close enough looking would be a semi-flat (not quite semi-gloss) black paint.

[Joe L.]

Re: 65 double grove water pump pulley

I parkerize them. This is manganese phosphate which comes out very dark gray to black. Same process as used on firearms. Zinc phosphate is a lighter gray color. Parkerizing is simple to do but requires clean metal (sand or bead blasted) and you need to heat the manganese solution. You can get the chemicals or a complete kit online from multiple sources. "Parkolac", as I understand it, was a black lacquer dip coating, not very permanent. Any originals with this coating have likely rusted long ago. Your best bet for durability is to "parkerize" which is manganese phosphate. Close enough looking would be a semi-flat (not quite semi-gloss) black paint.

Edward-------


I don't think the Parcolac was black in color, at least not the formulation specified by GM. I believe it was clear to slightly yellowish. Generally, I believe it was specified by GM for use on components that had been phosphate finished prior to the application of the Parcolac. Once-in-awhile it was used over bare metal. I believe the attached photo of an NOS GM #3868892 [not for sale] is a rare example of the use of Parcolac over a bare steel pulley. This pulley is 55 years old and it's pretty rust free, so it's held up pretty well.

[Gary B.]

Re: 65 double grove water pump pulley

Joe,

If Ricard Fortier is correct that the Parkolac was applied post black phosphate, then I think it's possible that the resulting part could have been on the dark gray end of the grayscale spectrum.

Gary