Finish on spindle support

[Joe L.]

Re: Finish on spindle support; painted thru '66?

Joe,

So is it you belief that the spindle supports were painted up thru '66 and then not painted starting with the '67 model year?

Gary

Gary------


Based upon the very limited amount of information we have, I would say yes. However, I think it would take a lot more "data points" from known original cars to really say so with any confidence. The information that Mark provided is very telling, though. Given that there was a change in foundry for the supports for the 1967 model year, that may indicate when the painting change was made.

I'd sure like to know a lot more about the manufacturing sequence and processes for these supports. To me, they've always been an interesting piece. However, if we knew more about the manufacturing sequences and processes we might be able to figure out more about when this painting changed.

I know for absolute certain that the supports on my 1969 were never originally painted.

[John H.]

Re: Finish on spindle support

If the machined surfaces are unpainted, then that means that the castings were painted subsequent to casting but prior to machining. So, they were either painted at some outside vendor (as is done today with all cast iron engine blocks and cast iron heads in a system called "component painting") and then shipped to a Chevrolet facility for machining or they were painted and then machined at some Chevrolet facility. It's also possible that both the painting and machining were done at some outside vendor facility. After all, the set-up and machining of these supports would have been a very specialized operation compared to ordinary passenger car parts and it might not have been economical for Chevrolet to set up to do it. If the machining was done at a Chevrolet facility, I expect it would have been Chevrolet-Warren.

Joe -

The trailing arm assembly (spindle support, trailing arm, caliper and bracket, splash shield, spindle, rotor, bearings, etc.) was done at Chevrolet-Warren; don't know for sure if the spindle support machining was done there or outside, but Warren had several paint facilities they used for control arms, etc.

[Gene M.]

Re: Finish on spindle support

The rear spindle supports are different from the mid years (total different from webless 63's) going to the c3. The bottom strut rod area is bigger around than the mid year configuration. That may be helpful in determining source of assemblies taken from unknown cars. This change may have something to do with the bigger strut rod ends of c3's.

[Mark G.]

Re: Finish on spindle support

Guys -

This is good as it gets; subject to interpretation.

Mark

[Ronald L.]

Re: Finish on spindle support

If any of this is truly paint, paint is organic in nature and will come up with paint remover to reveal the iron underneath.

A black oxide is molecular and is part of the surface, will not come up, would only change by hitting it with acid.

I did have a part I purchased in the 70's and it was raw iron right out of the box, FWIW.

[Gary B.]

Re: Finish on spindle support

Mark,

Are "Strut Rod Extension" the same as spindle supports?

Gary

[Mark G.]

Re: Finish on spindle support

Gary -

Yes, the note and change block are from the spindle support drawing #3820643. The note refers to the coating/paint drawing which shows the breakdown of the different material/processes used on the parts.

I think the cars were made to look good to sell; no rust, pitts, or unusual finishes. I'm not sure about service parts, probably just finish them to blend in with the background. BTW I use mineral oil on bare metal to avoid rust/ corrosion. Silicone paste works too but is stickier.

Mark

[Ronald L.]

Re: Finish on spindle support

Mark, thanks for posting, I remember Pontiac Varnish Company...Wide Track Drive...that's going back a few years.

[Gary B.]

Re: Finish on spindle support

Guys -

This is good as it gets; subject to interpretation.

Mark

Doesn't the specification that "Machined surfaces are not to be painted" imply that the part was painted after machining, not before?

It seems that some previous postings postulated that the part was painted, then machined.

Gary

[Ronald L.]

Re: Finish on spindle support

The one photo here sort of looks like it was masked off, would have been easier to paint then machine.

[Joe L.]

Re: Finish on spindle support

The rear spindle supports are different from the mid years (total different from webless 63's) going to the c3. The bottom strut rod area is bigger around than the mid year configuration. That may be helpful in determining source of assemblies taken from unknown cars. This change may have something to do with the bigger strut rod ends of c3's.

Gene------


The early C3 spindle supports were the same as 64-67. The change in spindle supports occurred for the 1975 model year with the change from the 64-74 casting, GM #3820643, to the 75-82 casting, GM #348103. The latter has the larger bosses at the ends of the fork for compatibility with the larger end strut rods also used for 1975-82. However, the 1975-82 supports and 1975-79 strut rods also became SERVICE for 1963-74 and could be used with original strut rods or supports.

[Joe L.]

Re: Finish on spindle support

Doesn't the specification that "Machined surfaces are not to be painted" imply that the part was painted after machining, not before?

It seems that some previous postings postulated that the part was painted, then machined.

Gary

Gary------


It would seem to me that the easiest way to paint the parts and keep the machined surfaces free of paint would be to paint the castings prior to machining. Then, the machined surfaces would all be "automatically" free of paint. The paint should not interfere much with the machining process, either. Of course, this is just my speculation and not necessarily how it was done. Otherwise, though, the machined areas would need to be somehow masked off prior to painting to keep them free of paint. This could be tedious and time-consuming, even in a factory environment set up for doing it most efficiently.

However, painting prior to machining is how it is done today for many castings. Ever see a recent vintage GM cast iron engine block or heads? All of the machined surfaces are free of paint (often to the detriment since some of the machined surfaces would be better off if they were painted). This is called "component painting". In this process, the raw castings are shipped to an outside vendor that paints them or powder coats them. Then, the castings are shipped to the engine plants where the painted or powder-coated castings are machined and assembled into engines. So, all of the machined surfaces are free of paint, it having come off with the metal in the machining operations. Some of the surfaces need to be free of paint, but others don't.

The primary purpose of component painting is to free the GM engine plants from having to have paint shops (and consequent air emissions). However, the quality of the painting is also vastly improved (except for those machined areas that don't need to be free of paint and end up rusting).

[Gary B.]

Re: Finish on spindle support

Joe,

I agree completely with you that it would be easiest to paint and then machine. I was merely pointing out that the specific wording on the document posted my Mark, however, suggests to me that painting was done after machining.

Gary

[Joe L.]

Re: Finish on spindle support

Joe,

I agree completely with you that it would be easiest to paint and then machine. I was merely pointing out that the specific wording on the document posted my Mark, however, suggests to me that painting was done after machining.

Gary

Gary-----


Yes, I agree that the wording does imply that. However, the method used to achieve that end could have been painting before machining. I don't really think this occurred, though, because I don't think that sort of processing was in common use at that time.