bolt finishes for a '70 chassis / suspension

[Steve G.]

I'm in process of restoring a '70 BB chassis / suspension and am trying to get bolt finishes correct. Does anyone knows correct finish for these:

- u-joint clamp bolts
- camber bolt / washer / nut
- bolts and stover nuts to hold upper control arm shafts to the frame
- upper and lower pivot bolts, large washers, and lock washers
- spring end bolts, castle nuts, and large washers for bushings
- fuel tank cross member mounting nuts, bolts, and washers
- fuel tank strap bolts
- bolts and lock washers that mount to top of pumpkin
- bolts to mount vacuum cannister and brass radiator overflow
- bolts and frensh locks to mount half shafts
- bolt, nut, spacer for under chassis E-brake plastic roller ass'y
- resr sway bar / bracket mounting bolts, nuts, washers

I can guess based on finish (or lack there of) left on my bolts, but they are fairly rusty and I am not sure if I am seeing any signs of cad plating or phosfate 'sparkles' even after cleaning the h/w above. Steve

[Steven B.]

Re: bolt finishes for a '70 chassis / suspension

Steve, I don't have mine with me right now but this may help from the NCRS Store:Product DescriptionProduct CodePrice1953-72 Chassis Restoration Guide
SK-19
$ 20.00


Good Luck,

Steve

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

I'm in process of restoring a '70 BB chassis / suspension and am trying to get bolt finishes correct. Does anyone knows correct finish for these:

- u-joint clamp bolts
- camber bolt / washer / nut
- bolts and stover nuts to hold upper control arm shafts to the frame
- upper and lower pivot bolts, large washers, and lock washers
- spring end bolts, castle nuts, and large washers for bushings
- fuel tank cross member mounting nuts, bolts, and washers
- fuel tank strap bolts
- bolts and lock washers that mount to top of pumpkin
- bolts to mount vacuum cannister and brass radiator overflow
- bolts and frensh locks to mount half shafts
- bolt, nut, spacer for under chassis E-brake plastic roller ass'y
- resr sway bar / bracket mounting bolts, nuts, washers

I can guess based on finish (or lack there of) left on my bolts, but they are fairly rusty and I am not sure if I am seeing any signs of cad plating or phosfate 'sparkles' even after cleaning the h/w above. Steve

Steve------

- u-joint clamp bolts

BLACK PHOSPHATE; FOR 1970 USED FOR AUTOMATIC TRANS CARS ONLY. BLACK PHOSPHATE U-BOLTS USED FOR MANUAL TRANS CARS.
- camber bolt / washer / nut

BOLT IS BLACK PHOSPHATE; ATTACHED CAM IS PLAIN STEEL; SEPARATE CAM IS ZINC PLATED; WASHER IS PLAIN; NUT IS BLACK PHOSPHATE

- bolts and stover nuts to hold upper control arm shafts to the frame

BOLTS ARE BLACK PHOSPHATE; NUTS ARE ZINC PLATED
- upper and lower pivot bolts, large washers, and lock washers

BOLTS ARE BLACK PHOSPHATE, WASHERS(RETAINERS) ARE PLAIN STEEL, LOCK WASHERS ARE PLAIN STEEL

- spring end bolts, castle nuts, and large washers for bushings

BOLTS ARE BLACK PHOSPHATE, CASTLE NUTS ARE PLAIN STEEL; LARGE WASHERS (INNER RETAINERS) ARE PLAIN STEEL

- fuel tank cross member mounting nuts, bolts, and washers

FLAT WASHER WAS ZINC, LOCK WASHER WAS PLAIN. I'M NOT SURE ABOUT THE BOLT AND NUT
- fuel tank strap bolts

BLACK PHOSPHATE
- bolts and lock washers that mount to top of pumpkin

AS I RECALL, BOLTS WERE ZINC PLATED, LOCKWASHERS PLAIN STEEL
- bolts to mount vacuum cannister and brass radiator overflow

I DO NOT RECALL
- bolts and frensh locks to mount half shafts

BOLTS WERE BLACK PHOSPHATE; FRENCH LOCKS WERE PLAIN STEEL
- bolt, nut, spacer for under chassis E-brake plastic roller ass'y

BOLT WAS ZINC PLATED
- resr sway bar / bracket mounting bolts, nuts, washers

BUSHING BRACKET CLAMP BOLTS WERE BLACK PHOSPHATE, TRAILING ARM BRACKET BOLTS WERE ZINC PLATED

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Thanks Joe. That was EXTREMELY helpful. Last statement said :


rear sway bar / bracket mounting bolts, nuts, washers
BUSHING BRACKET CLAMP BOLTS WERE BLACK PHOSPHATE, TRAILING ARM BRACKET BOLTS WERE ZINC PLATED

Is that the 'trailing arm' part of the sway bar, or were you referring to something on the trailing arm?

Also, I found a plater that would do zinc and cad plating. I was told by someone I should simply do cad plating for any part that was supposed to be zinc plated, cad plated, or 'natural steel' as it looks similar, but lasts longer. Do you agree with that? Also, what finish should I ask for when re-plating the front caliper brackets? thanks so much, Steve

[Patrick H.]

Re: bolt finishes for a '70 chassis / suspension

I think that there is a difference between the appearance of cad and zinc in replated parts, and would opt for zinc. I remain of the opinion that few, if any, C3 parts were cadmium plated and would deduct if I noted the difference.

The way these cars are currently driven zinc will last longer than we will.

Patrick

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

Thanks Joe. That was EXTREMELY helpful. Last statement said :


rear sway bar / bracket mounting bolts, nuts, washers
BUSHING BRACKET CLAMP BOLTS WERE BLACK PHOSPHATE, TRAILING ARM BRACKET BOLTS WERE ZINC PLATED

Is that the 'trailing arm' part of the sway bar, or were you referring to something on the trailing arm?

Also, I found a plater that would do zinc and cad plating. I was told by someone I should simply do cad plating for any part that was supposed to be zinc plated, cad plated, or 'natural steel' as it looks similar, but lasts longer. Do you agree with that? Also, what finish should I ask for when re-plating the front caliper brackets? thanks so much, Steve

Steve-----


I was referring to the sway bar brackets that attach to the rear of the trailing arms.

I agree with Patrick; I think that the vast majority of "silver" plated pieces on C3's were zinc and not cadmium.

The front caliper brackets were zinc plated with a chromate (gold) overplate. The way the process was done, the chromate appeared very dull, not shiny, at all.

[Michael G.]

Re: bolt finishes for a '70 chassis / suspension

If properly plated, only a plating expert can recognize the very slight hue difference and identify the difference between zinc and cad. If either plating is chromated, all bets are off.

Regarding corrosion performance: If plated to the same thickness and not chromated, cad is much, much, much better than zinc.

The bottom line is that plating thickness is very important: if you use at least 3-5 tenths thick cad you'll never have worry about it again. If you use zinc, have it plated thicker and have a clear chromate sealer applied. It will look just like cad, and, on a slightly driven car, it will last a long, long time.

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Thanks to all. I will go with zinc plating instead of cad. And will ask for thickness greater than 5 mils.

I was originally told I should get brake dust shields done in cad as well. After reading Judging Guide this AM, I see it lists zinc for those as well - anyone agree or disagree with zinc for these?

Should bell housing to engine block be zinc as well?

For 'unplated' bolts, I am going with some sort of protection on them. Any thoughts as to whether I should spray clear satin lacquer or use zinc or cad there? Steve

[Steve G.]

Re: bolt finishes for a '70 chassis / suspension

Also, the long radiator support bolts with large washers (long 'fingers') look to be a dull gray on my car. Anyone know if this is gray phosfate, cad, or other finish? Steve

[Terry M.]

Re: bolt finishes for a '70 chassis / suspension

Thanks to all. I will go with zinc plating instead of cad. And will ask for thickness greater than 5 mils.

I was originally told I should get brake dust shields done in cad as well. After reading Judging Guide this AM, I see it lists zinc for those as well - anyone agree or disagree with zinc for these?

Should bell housing to engine block be zinc as well?

For 'unplated' bolts, I am going with some sort of protection on them. Any thoughts as to whether I should spray clear satin lacquer or use zinc or cad there? Steve

Rear brake dust shields were punched (blanking is the proper name) from galvanized sheet, so the finish is galvanized with the edge natural steel. Now try and duplicate that. One low mileage 1972 has red "ARMCO" printing on the backing plate, so it is a cousin to road barrier.

Front brake dust shields are probably zinc plated. As Patrick said there are few places they would have spent the money for cadmium.

I'm pretty sure the bell housing to engine fasteners are black, but wait and see what some of the bolt gurus say. Any coating you put on the fasteners is not like the original, and makes me wonder why you are asking about original finishes when you intend to put your own coating on them anyway.

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

Rear brake dust shields were punched (blanking is the proper name) from galvanized sheet, so the finish is galvanized with the edge natural steel. Now try and duplicate that. One low mileage 1972 has red "ARMCO" printing on the backing plate, so it is a cousin to road barrier.

Front brake dust shields are probably zinc plated. As Patrick said there are few places they would have spent the money for cadmium.

I'm pretty sure the bell housing to engine fasteners are black, but wait and see what some of the bolt gurus say. Any coating you put on the fasteners is not like the original, and makes me wonder why you are asking about original finishes when you intend to put your own coating on them anyway.

Terry------


Once-upon-a-time I took tiny scrapings from a variety of "silver colored" and irridite (chromate) plated parts on my 1969, solublized the scrapings in hydrochloric acid, and analyzed via atomic absorption spectrophotometry. NONE of the pieces I checked were cadmium plated; all were zinc.

I think the bellhousing-to-engine block bolts were zinc plated. They definitely were on my 1969 300-350.

[Terry M.]

Re: bolt finishes for a '70 chassis / suspension

Terry------


Once-upon-a-time I took tiny scrapings from a variety of "silver colored" and irridite (chromate) plated parts on my 1969, solublized the scrapings in hydrochloric acid, and analyzed via atomic absorption spectrophotometry. NONE of the pieces I checked were cadmium plated; all were zinc.

I think the bellhousing-to-engine block bolts were zinc plated. They definitely were on my 1969 300-350.

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

Terry------


I've lost access to the lab now since I retired, too. If there was still anyone working there that I knew, I could probably still "mooch" a little, but all that I knew are gone now.

I believe the difference in the plating for the disc brake shields is due to the fact that the rear shields were manufactured to a Delco-Moraine specification. However, the front shields were manufactured to a Chevrolet specification.

[Edward J.]

Re: bolt finishes for a '70 chassis / suspension

Joe, not to buck the zinc on the bell housing bolts, but my 72 are black phosphate. Auto. trans., like everything that gets discussed with finishes there seems to be more than one supplier, and I can tell you I have seen zinc bolts also.

[Joe L.]

Re: bolt finishes for a '70 chassis / suspension

Joe, not to buck the zinc on the bell housing bolts, but my 72 are black phosphate. Auto. trans., like everything that gets discussed with finishes there seems to be more than one supplier, and I can tell you I have seen zinc bolts also.

Edward-----

Are you saying that your 72 is an automatic transmission? The bolts were different for auto versus manual transmission. Auto transmission used a standard hex head bolt of 3/8-16 X 1-3/8" and of GM #179842. This bolt was GM 280M material grade (SAE grade 5; 3 lines) and it was of "plain" finish ("plain" finish may appear dark brown or black). These bolts were installed at St. Louis.

Manual transmission bellhousing-to-block bolts were FLANGED hex head and of 3/8-16 X 1-1/4". These were also of GM 280M material grade. All that I have seen were zinc plated. These bolts were installed at the engine plants and not at the vehicle assembly plants.