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Old 09-10-2018, 06:12 PM   #1
mikebGMC70
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Drum proportion valve

Doing a disc conversion with an Astro van booster on a 70 C20. Question is can I used my old drum/drum proportion valve or switch over to a disc/drum one. Previous owner ran new brake lines and was seeing if I could keep them. Thanks
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Old 09-10-2018, 06:37 PM   #2
Mike C
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Re: Drum proportion valve

Technically the drum block is a distribution block and not a proportioning block aka Combination Valve. You need a combination valve for the disc brake setup.
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Old 09-10-2018, 06:49 PM   #3
mikebGMC70
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Re: Drum proportion valve

I snag a proportion valve off an old g van since they seem to go unmolested in pick n pull yards.
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Old 09-10-2018, 07:54 PM   #4
AussieinNC
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Re: Drum proportion valve

What master cylinder do you intend to use?

Suggest you get a true disk / drum style master as drum/drum has line valves in the ports to keep a small amount of line pressure in lines to keep rubber cups out against wheel cylinder bodies...

Disk calipers can bind up if the valves are not removed from drum / drum masters...

Much better to use disk/drum system and correct proportioning valve...

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Old 09-10-2018, 08:14 PM   #5
Steeveedee
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Re: Drum proportion valve

Quote:
Originally Posted by AussieinNC View Post
What master cylinder do you intend to use?

Suggest you get a true disk / drum style master as drum/drum has line valves in the ports to keep a small amount of line pressure in lines to keep rubber cups out against wheel cylinder bodies...

Disk calipers can bind up if the valves are not removed from drum / drum masters...

Much better to use disk/drum system and correct proportioning valve...

Yes, X 3. Also, the Astrovan booster will be designed for a different weight distribution than the truck, so should not be used.
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Old 09-10-2018, 08:58 PM   #6
mikebGMC70
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Re: Drum proportion valve

I have a new MC for a 73+ 3/4. My setup looks like this. I thought the Astro van booster was what a lot of folks was running?
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Old 09-10-2018, 09:31 PM   #7
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Re: Drum proportion valve

Hydroboost from an Astro is fine.

I have one installed on my Suburban
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