KH question

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Thanks for replies, here are some pics. Easier to see the divots with a few minutes of filing on them. I tried measuring, best I can tell is approx 0.050" on the deepest.
Yes Jim, they do start to add up in price. I needed 8 new pistons and seals, but had never tackled a rebuild on these, so the challenge is/was on.
Thanks all.




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Steve after seeing how much sheep you are going through with your calipers, I just bought the set that JV had, it will cost a bit to get them home here in Ontario but need better brakes on my Cuda.
Dave
 
Sheep? You mean ****?? Lol
No issues here, just questions is all.
I bought these a while back and i would rather learn to rebuild them as I can use them on 67 and 9, then pay someone else to do them.
Lol, I bet you will have more in shipping than I do in new parts.
Cheers
Steve after seeing how much sheep you are going through with your calipers, I just bought the set that JV had, it will cost a bit to get them home here in Ontario but need better brakes on my Cuda.
Dave
 
Sheep? You mean ****?? Lol
No issues here, just questions is all.
I bought these a while back and i would rather learn to rebuild them as I can use them on 67 and 9, then pay someone else to do them.
Lol, I bet you will have more in shipping than I do in new parts.
Cheers
where did you buy you rebuild parts for the calipers from?
 
Thanks guys! I read on Scotts thread where he took your advice Jim and filed his down. My concern was "too much" filing.
MO, when you say "stuck pads" are you talking the outer circumference of the piston bore? If so, that area has some flash rust after sitting in and coming out of Evaporust.
Thanks guys, sorry pics are lousy, hard to get close up of the proper area.
Oh couple more questions, what's so special about "caliper paint"? I was going to use Duplicolor engine enamel. Its high heat so shouldn't it be ok to use?
Also got new pistons. Bore/diameter is identical to old ones, but height is shorter on new ones approx 0.08" Foreseeable issues?

Cheers
Steve




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Pictures show what I alsways found - its pistons that rust. They should have a chrome finish that is perfect. No flaking.
Get the stainless ones. There's no difference in diameter between Mustang, Corvette and Mopar A-body pistons.
There was a slight change in early vs later caliper seals or something.
I don't recall the details. Lusk has posted about that.

Those calipers are never going to get that hot to bubble the paint off them.
I agree. The rotors get hot. The linings get hot. Eventually some heat directly transfers to backing plate, then to the pistons, to the fluid and then the calipers.
The rest of the heat goes into the air, and some portion of that transfers to the caliper surface.
An engine or barbque paint should handle it fine.

FWIW I have temperature sensitve paint on the disks, calipers, and edges of the pads. Still haven't got even the pad backing plates hot enough to begin change color (roughly 550*F). That includes some road course time. Getting off topic, but the reason I monitor this was because of the intended use on road courses and I wanted a sense of what temperatures the linings were seeing.

A little more on temperatures the ROTOR may see.
Temperature rise calculations using the method in Fred Puhn's Brake Handbook.

Temperature Rise in Front Rotors
3400 lb A-body with factory 4 piston calipers and 10x1.75 rear drums:
60 mph
stop calculates to 107 F degrees
same 60 mph stop if the rear drums did nothing, the disks would still only increase 147 F degrees.

120 mph stop the temperature rise will be 430 F degrees
and if the drums did nothing it still only calculates to 590 degrees.

Remember that's the rotor and the pad lining. So even on a 100 *F day, this is well in the performance capability of any decent street pad.

The reason I ran those calculations was SHO Times article.
Ford's SHO cars were initially equiped with a notriously small brakes for the size and weight of the cars.
The article's author ran the same calculations for various SHO brakes and also made real life measurements.
This made an interesting and useful comparison with our cars.

Stock 1989 Ford SHO with 10.1" rotors
60 mph stop, the front rotors would experience about 220 F degree rise in temperature.

120 mph stop, the 10.1" rotors will increase temperature around 750 F degrees.

Those ballpark calculations can be compared with measurements where he made repeated stops with his '89 SHO.
"...measured 385 F on my front rotors in rush hour traffic on a 45 mph street because of several sequential stoplights.
...four back to back 60 mph stops generated 550 F."
 
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