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Old 11-01-2013, 04:57 PM   #1
jbailey
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Location: Valley Springs CA
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70 drum to disk

Ok have you ever read so much you just confuse your self more?

That is where I am at so thought I would throw it out there make sure I am on the right track.

I have a 70 with a power booster and M/C can I use for disk in the front and drums in the rear. My original plan was to buy a new booster and M/C but if I can reuse mine why not?

So can I just buy the proportioning valve for a disk/drum one? And could I use the adjustable one that mounts on the frame rail near the rear brakes?

I have been doing a restore on this truck and just got the cab back on the frame and hoping to start putting back together.

Here is a link to my build
http://67-72chevytrucks.com/vboard/s...d.php?t=600795

And thanks for the help
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Old 11-01-2013, 11:17 PM   #2
Longhorn 70
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Re: 70 drum to disk

I did my C20 front Drum to Disc. I did change the master cylinder for a 71 with disc brake cylinder. The disc/drum cylinders do have a bigger bore. Truth be told the original one did work OK but not as well as the new bigger bore.

I had to shorten the pushrod in the booster as the drum/drum master had a deeper cylinder bore. The didtribution block should be changed to a proportioning valve for disc/drum. In the first pic you can see the new proportioning valve. Note that if you have a C20 or C30 you cross the brake lines from the master. You leave them uncrossed if you have a C10.

The second pic is what the disc install ended up looking like. If I had to do it again I definately would!

You'll like the better stopping power especially in deep water. Good luck buddy. And Welcome to the board.
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1970 Longhorn, Front Disc, 350/4 bolt, 882 heads, HEI, Edelbrock, 700R4, HO-52/4.11.
1996 Corvette, Collector Roadster, LT4, 396, 450RWHP, 6sp, 4.11/Dana44/posi 5 point roll bar

And let us not grow weary of doing good, for in due season we will reap, if we do not give up. Gal 6:9

Last edited by Longhorn 70; 11-01-2013 at 11:30 PM.
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Old 11-02-2013, 09:40 AM   #3
jbailey
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Re: 70 drum to disk

Thanks for the info.

Just to be clear I should replace the M/C and the proportioning valve? I will do some research on the push rod I am sure its explained on this site some where.

any one have experience with the proportioning valve that mounts on the frame rail near the back? just wondering if that would be better because it is adjustable.
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Old 11-02-2013, 01:44 PM   #4
WIDESIDE72
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Re: 70 drum to disk

Yes you need to change mc and prop vale when switching from drum to disc. I have never messed with the brake rod when doing this but the two i did already had power brakes. I used the existing boosters i both as well
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Old 11-02-2013, 06:52 PM   #5
jbailey
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Re: 70 drum to disk

Got it. Keep booster and replace M/C and proportioning valve. Thanks
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Old 11-03-2013, 05:43 PM   #6
ReeseBobby
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Re: 70 drum to disk

I didn't replace the M/C when I did mine on the K20. I might eventually but it's fine so far. You could always try it as is.
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