How to convert your early cab to accept modern brake master cylinder - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tx Firefighter · 08-06-2009, 05:52 PM

I took some pictures today as I worked on my truck. It's too hot to work now, so I figured i would do a little tech piece for anyone who has an early cab and wants modern brakes.

My cab is a 62 model. It's the one that takes the dual master cylinder and clutch cylinder combo. I am running a turbo 350 trans now, so I have no need for the clutch part of the deal.

Problem is, the early cabs use a funny diagonal bolt pattern and later model master cylinders use a horizontal bolt pattern.

First, this is the beginning before teardown...

Once the old dual master cylinder combo is removed, you are left with this. None of the holes are conducive to modern units...

This is a later cab (a 63). Notice that along with the funny diagonal hole pattern, there is the horizontal pattern we want...

First, we need to weld up all of the unnecessary holes. Just leave the 4 pictured here. Notice I painted the firewall between pictures, but it's the same early cab as the first picture...

So, I removed the brake pedal box from a later model cab, cleaned it up, and fit it to my early cab. The later pedal box is a straight bolt in other than a tiny bit of grinding needed around the old clutch hole. You can see in this inside shot where I had welded a round patch into the old clutch hole. You will need to grind a bit on the little lip around the old hole...

Outside pic, note the newer box bolts into the same 4 holes we left...

Go back inside and backdrill the two horizontal master cylinder holes, through the bracket and through the firewall. Here is a punch in one of the spots...

The other hole that needs backdrilled...

Now, all you have to do is bolt the later model master cylinder into place and you're ready for disc brakes..

No real money spent on this deal. In my eyes, this is much better than ordering a kit from some place.

**slepysal** · 08-06-2009, 09:10 PM

very nice.I will be converting my 60 soon and this helps a bunch thanks

63sbssbbw · 08-07-2009, 06:43 AM

That's awesome Kevin
Looks like a whole lot less work than my original plan
Thanks for sharing
T

markeb01 · 08-07-2009, 08:56 AM

Excellent! Great information and presentation, very clear and easy to follow.

MacAttack · 08-07-2009, 09:55 AM

Outstanding, Kevin. Really concise and very practical.

**slepysal** · 08-15-2009, 04:13 PM

Any mods to the push rod ?

Tx Firefighter · 08-15-2009, 08:24 PM

No pushrod mods needed. I reused the stock one.

*LILRED66* · 08-16-2009, 11:56 AM

Nice work and thanks for the write-up.

08-06-2009, 05:52 PM	#1
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	How to convert your early cab to accept modern brake master cylinder I took some pictures today as I worked on my truck. It's too hot to work now, so I figured i would do a little tech piece for anyone who has an early cab and wants modern brakes. My cab is a 62 model. It's the one that takes the dual master cylinder and clutch cylinder combo. I am running a turbo 350 trans now, so I have no need for the clutch part of the deal. Problem is, the early cabs use a funny diagonal bolt pattern and later model master cylinders use a horizontal bolt pattern. First, this is the beginning before teardown... Once the old dual master cylinder combo is removed, you are left with this. None of the holes are conducive to modern units... This is a later cab (a 63). Notice that along with the funny diagonal hole pattern, there is the horizontal pattern we want... First, we need to weld up all of the unnecessary holes. Just leave the 4 pictured here. Notice I painted the firewall between pictures, but it's the same early cab as the first picture... So, I removed the brake pedal box from a later model cab, cleaned it up, and fit it to my early cab. The later pedal box is a straight bolt in other than a tiny bit of grinding needed around the old clutch hole. You can see in this inside shot where I had welded a round patch into the old clutch hole. You will need to grind a bit on the little lip around the old hole... Outside pic, note the newer box bolts into the same 4 holes we left... Go back inside and backdrill the two horizontal master cylinder holes, through the bracket and through the firewall. Here is a punch in one of the spots... The other hole that needs backdrilled... Now, all you have to do is bolt the later model master cylinder into place and you're ready for disc brakes.. No real money spent on this deal. In my eyes, this is much better than ordering a kit from some place. __________________ I'm on the Instagram- @Gearhead_Kevin Last edited by Tx Firefighter; 09-01-2009 at 01:19 PM.

08-06-2009, 09:10 PM	#2
slepysal Registered User Join Date: Oct 2006 Location: San Jose NOR*CAL Posts: 3,080	Re: How to convert your early cab to accept modern brake master cylinder very nice.I will be converting my 60 soon and this helps a bunch thanks __________________ 1960 Apache long bed fleet L6 250 Clifford intake 2 bbl carb. Langdon cast headers with dual exhaust and bellflower tips. T-5 5 speed, power steering and power disc brakes. "Over, Around or through it... "

08-07-2009, 06:43 AM	#3
63sbssbbw UCA63 Join Date: Aug 2005 Location: Lloydminster AB Can. Posts: 1,637	Re: How to convert your early cab to accept modern brake master cylinder That's awesome Kevin Looks like a whole lot less work than my original plan Thanks for sharing T __________________ member#7816 "63 sb ss bbw 350\350 12 bolt rear Pwr Fr Disc PS tilt '61 GMC in progress '63 GMC to use for parts '90 Chevy Ext cab sbfs 5.7l (current d d)

08-07-2009, 08:56 AM	#4
markeb01 Senior Enthusiast Join Date: Feb 2007 Location: Spokane Valley, WA Posts: 8,356	Re: How to convert your early cab to accept modern brake master cylinder Excellent! Great information and presentation, very clear and easy to follow.

08-07-2009, 09:55 AM	#5
MacAttack 283 Drama Queen Join Date: Dec 2004 Location: Surf City, CA Posts: 2,435	Re: How to convert your early cab to accept modern brake master cylinder Outstanding, Kevin. Really concise and very practical. __________________ For about 12 years of my adult life I had a severe speech impediment. My ex-wife never let me get a word in edgewise.

08-15-2009, 04:13 PM	#6
slepysal Registered User Join Date: Oct 2006 Location: San Jose NOR*CAL Posts: 3,080	Re: How to convert your early cab to accept modern brake master cylinder Any mods to the push rod ? __________________ 1960 Apache long bed fleet L6 250 Clifford intake 2 bbl carb. Langdon cast headers with dual exhaust and bellflower tips. T-5 5 speed, power steering and power disc brakes. "Over, Around or through it... "

08-15-2009, 08:24 PM	#7
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: How to convert your early cab to accept modern brake master cylinder No pushrod mods needed. I reused the stock one. __________________ I'm on the Instagram- @Gearhead_Kevin

08-16-2009, 11:56 AM	#8
LILRED66 Account Suspended Join Date: May 2005 Location: Kansas City, KS Posts: 3,906	Re: How to convert your early cab to accept modern brake master cylinder Nice work and thanks for the write-up.

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