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Old 09-12-2019, 06:13 PM
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Default upgrade to power disc brakes?

Having changed over to power steering (and very happy with the change) I was leaning towards upgrading from manual-drum to power-disc brakes (I found a mint pair of calipers/backing plates on local CL ad) but would my factory JT wheels still work ?

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Old 09-12-2019, 06:41 PM
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do it .... just look at the bottom of the spindle where the inner race rides and look for wear...
or heavy hammer marks from disassembling around the ball joint holes...

JT 's are often 70 model

so yes they would clear the caliper ....

JC are the drum code fairly sure

Scott

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Old 09-12-2019, 07:55 PM
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You don't need to go to power either - we did a 68 with the drum manual master and it stops quite well

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Old 09-12-2019, 08:34 PM
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JT wheels work with disc

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Old 09-12-2019, 10:03 PM
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We added manual disks to a '67 Bird many years ago. Great upgrade & no clogged up real estate under the hood.

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Old 09-13-2019, 09:21 AM
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Quote:
Originally Posted by Scarebird View Post
You don't need to go to power either - we did a 68 with the drum manual master and it stops quite well
I have a 72 lemans with 4-wheel drums that I'm thinking about converting to manual front disc. Are you saying that the manual drum master cylinder would work with the disc brakes? I was under the assumption that you would need a mc with a larger reservoir and smaller piston bore?

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Old 09-13-2019, 11:21 AM
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The bore is the same, larger reservoir is for pad wear - watch the fluid level and you should be fine

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Old 09-13-2019, 03:50 PM
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How about the proportional and delay valves, I'd think they are disc or drum specific?

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Old 09-13-2019, 07:52 PM
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We used neither to test; the fronts locked up first. I have found no use for delay valves.

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Old 09-17-2019, 08:37 AM
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Quote:
Originally Posted by Scarebird View Post
The bore is the same, larger reservoir is for pad wear - watch the fluid level and you should be fine
Cool thanks!
Another question, will the front drum proportional valve work? I don't believe 72's have the delay valves? Can you just swap the front disc assembly and leave everything else as is?

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Old 09-17-2019, 04:03 PM
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You could, but I would plumb in an adj. prop valve in the rear line so you can dial in the initial bias

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Old 09-17-2019, 08:01 PM
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[QUOTE=Scarebird;6062908]You could, but I would plumb in an adj. prop valve in the rear line so you can dial in the initial bias[/QUOTE

Is there a prop valve for a manual disc/drum or is the adjustable the only way to go? Sorry for hijacking and so many questions, just trying to figure out if this is doable without having to buy a whole "kit". Thanks again

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Old 09-17-2019, 11:50 PM
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[QUOTE=Holeshot71;6063006]
Quote:
Originally Posted by Scarebird View Post
You could, but I would plumb in an adj. prop valve in the rear line so you can dial in the initial bias[/QUOTE

Is there a prop valve for a manual disc/drum or is the adjustable the only way to go? Sorry for hijacking and so many questions, just trying to figure out if this is doable without having to buy a whole "kit". Thanks again
this is what we recommend:

https://www.summitracing.com/parts/s...0aAqbKEALw_wcB

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Old 09-18-2019, 12:08 AM
Baron Von Zeppelin Baron Von Zeppelin is offline
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The difference between 1970 JL and JT code rally2 wheels were just a running change during production when they switched from Black Center Caps (JL) - to Red (JT).

Both codes work with disc and drum in 1970

67-69 were the years where they had 2 separate codes JA & JC that were application specific.

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Old 10-14-2019, 11:10 PM
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Thanks everyone. Definitely adding this to list of winter projects


Sent from my iPhone using Tapatalk

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Old 10-15-2019, 11:54 AM
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Quote:
Originally Posted by Baron Von Zeppelin View Post
The difference between 1970 JL and JT code rally2 wheels were just a running change during production when they switched from Black Center Caps (JL) - to Red (JT).

Both codes work with disc and drum in 1970

67-69 were the years where they had 2 separate codes JA & JC that were application specific.
there is a slight offset difference between JL & JT rally II wheels, the change in center cap color was by and large a coincidence. Early '70 A-bodys with disc (& GP's) used the bolt on outer hub design "2 piece" rotor same as was used on '67-69 disc brake A & F body's. The two piece rotors had a different dimension from the back of the rotor to the front edge of the wheel mounting surface than was used with the 1 piece rotors. When Pontiac changed from 2piece rotors to what is today the very common one piece style, they also changed wheel codes. Chevrolet did the same on their SSI wheel (YA's to AO's).

Either wheel will fit with OEM '69-72 caliper brackets & rebuilt OEM or proper replacement calipers.

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Old 10-15-2019, 01:07 PM
Baron Von Zeppelin Baron Von Zeppelin is offline
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Cool factoid on that.
Was never even aware early 70 used 2 piece rotors like a 69.


Never been a fan of the red center caps either.

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