'68 El Disc Brake Conversion Question - Chevelle Tech
Brakes, Suspension & Steering Conversion questions & more.

 
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post #1 of 7 (permalink) Old Apr 30th, 19, 7:03 PM Thread Starter
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David
 
Join Date: Apr 2019
Location: SW Colorado
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'68 El Disc Brake Conversion Question

So I bought a junker '69 with the intention of robbing the disc brakes. If you're thinking about doing the same, my advice is Buy A Kit! About the only usable parts were the spindles and caliper brackets. So I ended up replacing backing plates, rotors, bearings and seals, hoses and loaded calipers. Now my question is do I need to change the master cylinder? The '69 doesn't have one. Can I use the drum brake MC and install a residual pressure valve on the front circuit? If so how many psi. Is the RPV contained in the proportioning valve? Do I need to change the proportioning valve? If you're wondering they are not power brakes. I'm not gonna get hurt on the '69 as it has a lot of good trim, glass and sheet metal. Thanks in advance for the help and advice.


later, dozer

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post #2 of 7 (permalink) Old May 9th, 19, 2:21 PM Thread Starter
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David
 
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Re: '68 El Disc Brake Conversion Question

Over a week and no response? Thanks, I'll figure it out on my own.

later, dozer

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post #3 of 7 (permalink) Old May 9th, 19, 2:48 PM
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jerry
 
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Re: '68 El Disc Brake Conversion Question

Yes, using oem donor brakes is similar to buying a Muncie at a swap meet....well not that risky.
You can easily mic the rotors to see if they're usable. If the backing plates are straight, you can have them replated or just spray bomb them, your preference. The booster probably needs rebuilt, but non-pitted cores are worth good money. The master is worth money but it'll likely be just a core. Like you said, the spindles are most likely good and the caliper brackets are also, but will likely need plating, or.... Now the calipers are easily rebuildable for cheap, unless they've seen setting moisture for long periods. Cheap, meaning less than $10 for the pair. If you're not caring about originality, a '71-'72 prop valve is the chit, and then buy all new lines for that year from your choice of vendors.
That's the advise if you're starting fresh. I say this because the kits run at least $800 and you're stuck with china metal, that is a whole lot riskier than rebuilding oem.
Done it myself but I was in a hurry, my bad. I've got less into my oem '69 setup and that includes rebuilding the master, calilpers, hold-off valve and booster and also the cost of replating the backers, brackets and booster....just took more time.
As for your master, that drum brake master isn't up to the task to pressurize the calipers. Not sure which one to use, but I'll bet it should have a 1" bore. You could call Wilwood and see what they offer for your app.
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post #4 of 7 (permalink) Old May 9th, 19, 4:11 PM
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kevin
 
Join Date: Sep 2008
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Re: '68 El Disc Brake Conversion Question

I put a complete right stuff kit on my '68 ss el camino - front and rear. The quality is "ok" - maybe lacking a bit from from the old factory stuff. It does work well and is nice and shiny. Several years ago (over 20) I did a front disc swap on my '67 ss chevelle from a 71 station wagon in the junk yard. I have to say I like the oem stuff better. I grabbed the prop valve and all the lines and booster from the old wagon. The rotors and calipers were still good and remain on the car to this day. Back then - $75 for the whole thing - then had the rotors turned and of course auto zone lifetime pads....
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post #5 of 7 (permalink) Old May 10th, 19, 2:27 PM
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Harold
 
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Re: '68 El Disc Brake Conversion Question

buy the right prop.valve , a MC for a 75 Corvette with manual brakes(others might work too) and a 3lb residual valve (may not need it but won't hurt)

New paint -near complete
66 SS 396. now 427
4sp w/GV, AC,PS,3.31 Posi,ft disc,11" r drum
86 Buick Grand National
89 K25 Suburban that I bought new,is new again
And a bunch of other junk.
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post #6 of 7 (permalink) Old Jun 11th, 19, 10:52 PM Thread Starter
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David
 
Join Date: Apr 2019
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Re: '68 El Disc Brake Conversion Question

Well it's been a while but the project is complete. Had to remove the left header and clutch linkage to get to the proportioning valve. Pulled the proportioning valve off the donor, rear brake line was different. Pulled the rear brake line off the donor. Purchased the correct MC from O'Reilly. Bench bled the MC, then bled the system, then tightened up the leaks, then re-bled the system, then tightened another leak, then re-bled the system. I had to go about 1/6 turn farther than what I thought was tight enough, hope I never have to take them apart. Replaced the left header and clutch linkage. Been driving it for about a week now. It took a lot longer than it should have because I kept having to wait for another paycheck. Don't really notice much improvement in braking but maybe it will add to the resale value when my heirs sell it.

later, dozer

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post #7 of 7 (permalink) Old Jun 11th, 19, 11:25 PM Thread Starter
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David
 
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Re: '68 El Disc Brake Conversion Question

Here it is!
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