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easy 66 dual master cylinder conversion

 
Old 03-13-2019, 05:48 PM
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rayL79
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Default easy 66 dual master cylinder conversion

I'm really enjoying my 66 L79 roadster that I bought 2 years ago and have driven way too little. This is a nice, positive story that I hope helps others. I knew from the beginning I wanted a dual master after almost losing the brakes due to an unseen leak into the passenger compartment. I agonized over how to do it for too long, looking at all the kits that are available on line, and getting some help from this Forum. I finally got it done today and it was way too easy (and inexpensive), and is easily reversible if someone want to go back to stock.
I simply bought a 1967 Corvette master cylinder (AC Delco) from RockAuto for something like 50 bucks. Then I got 2 flare adapters (one 9/16 to 7/16 and one 1/2 to 7/16 to convert the master cylinder outlets to accept standard 1/4" tubing fittings which are on the brake lines in the car. I also needed a 7/16 flare plug to put into the brass block where the rear brakes used to come from.
I had my local trusted mechanic (not a Vette guy) do the work and he charged me for an hour and a half.
All he had to do was:
Bench bleed and install the new master cylinder
Re-bend the front brake line which now had to enter from the side instead of the front.
Remove the rear brake line from the brass block in front and re-bend the line to hook up to the rear outlet of the new cylinder.
Put a plug in the block where the rear brakes used to be fed.
Bleed the system.
The brakes feel great and lock up if you stomp on the pedal just like before.
The whole thing cost me a little over $200 (labor included) and I would recommend it to anyone driving a 65 or 66 with manual brakes.
Ray
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Old 03-13-2019, 06:24 PM
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Avispa
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Thanks for that, ray. The feds made the OEMs put those things in for '67 for a reason. That and collapsible steering columns, fully padded dashboards and plastic or rubber shields around the window cranks, radio *****, heater controls and mirror. Pre-67 cars were kinda death traps.
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Old 03-13-2019, 06:47 PM
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Tom Austin
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Hi Ray,

Happen to have any photos of the finished project? Thanks!

Tom
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Old 03-13-2019, 07:15 PM
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Mike mgchevy
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Originally Posted by Avispa View Post
Thanks for that, ray. The feds made the OEMs put those things in for '67 for a reason. That and collapsible steering columns, fully padded dashboards and plastic or rubber shields around the window cranks, radio *****, heater controls and mirror. Pre-67 cars were kinda death traps.

I'll take that death trap off your hands, at a discount of course. Probably will have to crush it due to it being so dangerous.
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Old 03-13-2019, 07:31 PM
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Very cost-effective investment in safety. Good job.

Steve
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Old 03-13-2019, 07:37 PM
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rayL79
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Old 03-13-2019, 07:39 PM
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Great post.

Where did did you get the flare adaptors?

Thanks
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Old 03-13-2019, 08:26 PM
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rayL79
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Matt,
I got the flare adaptors locally at AutoZone and AdvanceAutoParts. They're pretty common...most parts stores have an assortment.
Ray
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Old 03-13-2019, 10:18 PM
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Nice!

There has been discussion on here, pro and con, about power brakes. Obviously you decided not to go with the booster etc. Any insight into your decision? I'm still on the fence with mine.
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Old 03-14-2019, 12:20 AM
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Larry Wegner
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I did't know it could be that easy! Great info, do you know if I can covert my 64 manual cylinder car using the 67 manual master cylinder the same as you did? I would like the safety update. Thanks.
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Old 03-14-2019, 05:48 AM
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Originally Posted by Railroadman View Post
Nice!

There has been discussion on here, pro and con, about power brakes. Obviously you decided not to go with the booster etc. Any insight into your decision? I'm still on the fence with mine.
I love the manual brakes...the car stops on a dime and the brakes feel great. I also had a 65 back in my younger days and I thought the same thing. I would never even think about adding a booster.
Ray
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Old 03-14-2019, 05:55 AM
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Originally Posted by Larry Wegner View Post
I did't know it could be that easy! Great info, do you know if I can covert my 64 manual cylinder car using the 67 manual master cylinder the same as you did? I would like the safety update. Thanks.
I don't think it's the same with the 63 and 64 drum brake cars. I believe they have a 7/8 bore master cylinder and the 67 cylinder is 1 inch. This will result in slightly higher pedal effort on your car. There may be other issues too...you should talk to someone who's done it.
Ray
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Old 03-14-2019, 06:06 AM
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Just to clarify something...I may have misspoken in my original post. 65's may have a 3/16 line going to the rear brakes instead of 1/4". If this is the case, you would need a different adapter for the rear port of the master cylinder- 9/16 to 3/8 I believe and a different plug for the brass junction block. I'm also assuming that a 65 has basically the same line routing as a 66. If I'm wrong I apologize.
Ray
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Old 03-14-2019, 10:00 AM
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Mike mgchevy
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Originally Posted by rayL79 View Post
I don't think it's the same with the 63 and 64 drum brake cars. I believe they have a 7/8 bore master cylinder and the 67 cylinder is 1 inch. This will result in slightly higher pedal effort on your car. There may be other issues too...you should talk to someone who's done it.
Ray
Actually all 4 wheel drum cars used 7/8" master 63-65

Last edited by Mike mgchevy; 03-14-2019 at 11:12 AM.
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Old 03-17-2019, 05:05 PM
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Does anyone know if this style conversion would work on a 63? I would love to do this on mine . Also what year master cylinder to use??
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Old 03-17-2019, 08:38 PM
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Originally Posted by rayL79 View Post



I did the exact same this when I first bought my '66. Same setup and without the balance block. Not sure if you painted yours before you did the install, I did not, so I keep a light coating of WD-40 on it to keep it from rusting. It still looks like new. If I ever have to remove it I'll paint it then. $.02 deposited.

Last edited by Tigershark3; 03-17-2019 at 08:39 PM.
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Old 03-17-2019, 08:50 PM
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Ray,
im glad you did the conversion, it's one of the first things I do to a 65 Or 66 non power brake car. It's nice isn't it, not sure why a lot of people argue with the added safety of this conversion.

however -


Someone should step in here on this conversion for 63 and 64 - is the 67 master cylinder compatible w drum brakes? I don't know, but I would hate for someone to find out the hard way.
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