T-arm surface question

[Kyle Zevena]

Gents,

I have finished bead blasting my t-arms and am wondering what the surface testure was originally. Should the finished surface look cast in appearance or should they be smooth? qusetion is how much grinding do I have to perform to prep the surface prior to paint? should they be pretty well smooth when painted?

I planned to use POR-15 and top with a semi gloss, any comments or experience from those who re-done thier arms would be appreciated.

[Joe C.]

Re: T-arm surface question

Kyle,

The t arms are formed sheet steel and should have a smooth surface. Any deep pitting should be prepared with surfacer/primer for best results. Originally, most chassis components were sloppily covered with an asphaltic based coating, which is available from Quanta. This is a very messy affair, and I do not recommend it except for a museum piece which is seldom driven. A more durable and cleaner alternative is your choice of semigloss/semiflat paint. I recommend Eastwood's chassis black, which comes in quart cans or spray bombs.

Joe

[Joe L.]

Re: T-arm surface question

Kyle------

The trailing arm external surfaces were a smooth steel----very much like that seen in ordinary sheet metal. They were not "mirror-smooth"; just like typical sheet metal. The machined surface which mates to the spindle support was usually not painted and rusts.

The trailing arms were painted a semi-gloss black; not quite a full gloss (as is seen in later GM SERVICE a-arms), but with significant gloss. While Corvette frames were finished with an asphaltic coating as Joe described, this was not the case for most other chassis components---they were painted, although the degree of gloss varied somewhat. This includes front a-arms, rear trailing arms, removeable crossmembers, most brackets, rear spindle supports (when painted), stabilizer bars (when painted), and other pieces.

Basically, only the frame and front steering linkage was finished with the asphaltic coating.

I do not recommend the use of POR-15 if you are trying to restore an original finish, even if you are going to apply paint over the POR-15. The POR-15 will result in a VERY non-original appearing finish. The finish will look WAY too thick and smooth. Even worse, when you find you don't like it, the POR-15 will be almost impossible to remove. A good quality paint will do everything you need it to do and it will look more-or-less as-original. POR-15 is for "show cars" and "hot rods"----not the restoration of Corvettes.

[Kyle Zevena]

Re: T-arm surface question

Thanks Joe and Joe.

Mr Lucia, you mentioned in a previous post that the backing plate (drum) is a gossier black finish, does this include the inerior surface? specifically the shoe contact areas, are they ground to bare metal? or were they originally painted also?

Thanks for all the great info, my reso of the rear suspension is going well and is almost as much fun as driving it....almost....

I think I will POR-15 the interior of the arms and simply prime the exterior to fill in the minor pits left. I used a 50 grit sanding disk to remove the larger pits leaving the welding "blobs" and inperfections they are now fairly smooth as far as the majority of the flat surfaces go.

[Joe L.]

Re: T-arm surface question

Kyle------

My recollection is that the drum brake backing plates were painted inside and out; perhaps, dipped. However, I'm not 100% sure about this. It's been so long since I was into one of these that I just don't recall, for sure.

[Michael H.]

Re: T-arm surface question

Kyle,

The brake shoe side of the backing plate would have been natural, unplated and unpainted. In fact, no part of the backing plate was painted when it was assembled to the control arm. Also, many of the components of the rear suspension/drive were assembled unpainted. When the entire assembly was complete, all of the unpainted surfaces received a coat of chassis black. It would include the differential, half shafts, spindle supports, backing plates and strut rods etc. The outer surface of the brake drum and spindle hub/wheel studs would also received a coating.

Chassis black can be described as having a gloss factor of about 70%, when new. Deep black, not the typical dark dark grey of a semi gloss spray can coating.

This entire paint peocess changed for the 65 model year. In fact, the paint operation was deleted completely for the rear susp/drive unit.

[Kyle Zevena]

Re: T-arm surface question

Thanks for the response Michael, I am now confused...

I don't have my JG handy, is the process you describe consistent with the JG? I was under the understanding that the carrier case, half shafts, lower shock mount and strut rods were natural, the t-arms, spindle supports and backing plate were painted.

Was the process you described done form the top of the car? were the top and bottom of the carrier, shafts and strut rods covered? or only the top surfaces?....

Other comments? I am getting ready to paint the trailing arms, strut support and backing plates, so I would like to know if I need to includue the strut rods, lower shock mount and inner flange or leave them natural as I had originally planned...

[Michael H.]

Re: T-arm surface question

Kyle,

I'm not sure what the JG calls for on this but I do know this was how it was done for 63-64. If you think back, you may remember that no brake backing plates were ever painted on the inside, (brake shoe side) at least for all 63-64 Corvette and passenger cars. (pretty sure this is also true for all C1) If this is the case, and it is, then the only way the inboard/visible side could have ever been coated is if the entire control arm assembly was coated at the same time. That would automatically include all of the previously mentioned components. There's no other logical sequence of assembly/paint that would be efficient and result in the components being coated the way they were.

As previously mentioned, this method of rear susp coating was eliminated for the 65 model year because of the fact that disc brake rotors would be difficult, or impossible, to shield from the spray.

The same is true for the front brake/knuckle assembly for 63-64. The entire assembly was coated before it ever reached the assembly line. The brake shoe side of the backing plate was absolutely raw, unpainted steel, but the back side was coated in black, along with the drum, hub, grease cap and spindle.

For 63-64, the half shaft was coated, along with the differential housing. When the entire assembly was hoisted up from the basement, there wasn't much of anything that wasn't coated. Not exactly what restorers want to hear, I'm sure, but this is the reality of it.

Pretty sure I have some decent pictures of the chassis line in the 63-64 era that clearly show these components in black. These shots are from the midway point of the chassis line, well before the chassis was flipped over, which is at least an hour before the final chassis blackout would have occured.

I would be interested in hearing what the 63-64 JG has on this subject.

[Kyle Zevena]

Re: T-arm surface question

Michael, the JG states that the items I mentioned are natural (spindle support, flanges, strut rods, carrir case, and rod supports) it did mention that original 63's may be "blacked out....

can you post the picture, sounds like it may shed some light on the subject...

[Michael H.]

Re: T-arm surface question

Kyle,

It would probably be easiest to just follow the JG at this point. If you restore the rear susp/drive to original, I'm not sure if anyone is going to accept it. Maybe Joe can explain how the backing plates are covered in black but the bearing housing is natural.

[Kyle Zevena]

T-Arm surface

Thanks Michael,

I think I'll take you advice on this one... looks like there may be an inconsistency as far as the 63-64 rear suspension finishes go.

[Michael H.]

Re: T-Arm surface

Thanks Kyle,

This is one of the items that is on the list of corrections for the judging guide. Not sure if it will actually be accepted but it is on the list. My guess is that this will be incorporated in the new printing but both coated and uncoated will be accepted. If I get time, I'll dig through the big box of pic's and post one or two that show the coating.

I certainly understand why so few have actually seen this on cars today as the original coating was usually gone within the first few years, especially on cars in wet or salt climates.