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Jul 21st, 2025 | | | | Joined: Jun 2012 Posts: 60 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2012 Posts: 60 | Is there a common dual master cyl. used for conversion into a 46 GMC , Chevy can't be much different ? Looking for advice and suggestions .
Allan
1946 GMC
1949 Mercury M68
| | | | | Joined: Nov 2005 Posts: 6,061 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,061 | Hy red1946, if you could give us a bit more information we could better answer your question, size of truck, stock drum brakes or upgrade to front discs or full disc brakes? There are a few suppliers for retrofit master cylinder kits, have a look at their websites, hope that helps. | | | | | Joined: Jun 2012 Posts: 60 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2012 Posts: 60 | Sorry . 46 GMC 1/2 ton . Willave a 4.3 litre V6 and a T5 trany with an S10 rear end . plan to leave the front end stock with drum brakes .
Allan
1946 GMC
1949 Mercury M68
| | | | | Joined: Oct 2010 Posts: 91 Shop Shark | | Shop Shark Joined: Oct 2010 Posts: 91 | Hey,red1946 If you are going keep the drum brakes I would consider upgrading to Bendix style.I swapped my Hucks to Bendix on my 46 one ton and the difference is night and day.Also the newer parts are available at any flaps.Not sure about master cylinder but I will follow this thread as I would also like to upgrade that as well. | | | | | Joined: Sep 2003 Posts: 1,820 Shop Shark | | Shop Shark Joined: Sep 2003 Posts: 1,820 | Really need to have "matching" brakes all the around.
"Truckin' Around .......... Since 1937!" My name is Joe and I am addicted to Classic Country Music. I just can't hep myself.Operators are standing by to take your calls! Now cruising in the Passing Lane | | | | | Joined: Oct 2007 Posts: 725 Shop Shark | | Shop Shark Joined: Oct 2007 Posts: 725 | I'd look for a "drum/drum" master with the same bore size as what you have now. Don't use a master for disk brakes! Talk to someone at your flaps and look the books for the mid-late '60s cars. Also '69-'70 Chevy and GMC light trucks.
best wishes,
Les | | | | | Joined: Jun 2010 Posts: 169 'Bolter | | 'Bolter Joined: Jun 2010 Posts: 169 | It seems there are all sorts of options for 47 and up. But for the 41 to 46 there are no master cylinder conversion kits or replacements. It must be due to the odd mounting of the MC on the 3 speed transmission. I would like to upgrade to discs and dual MC, but there is nothing that "bolts in". | | | | | Joined: Jun 2012 Posts: 60 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2012 Posts: 60 | Thanks guys sounds like good advice . One question , I am not familiar with the term ( flaps ) .
Thanks
Allan
1946 GMC
1949 Mercury M68
| | | | | Joined: Oct 2010 Posts: 91 Shop Shark | | Shop Shark Joined: Oct 2010 Posts: 91 | Friendly Local Auto Parts Store | | | | | Joined: Dec 2004 Posts: 1,897 Shop Shark | | Shop Shark Joined: Dec 2004 Posts: 1,897 | It seems there are all sorts of options for 47 and up. But for the 41 to 46 there are no master cylinder conversion kits or replacements. It must be due to the odd mounting of the MC on the 3 speed transmission. I would like to upgrade to discs and dual MC, but there is nothing that "bolts in". The solution here is to get the clutch and brake pedal setup from a larger truck of the era. The MC was frame mounted, with the actuator rod facing toward the rear of the truck. The set up worked like this, when the brake pedal was pushed, a rod and clevis was attached to it in a way that created a pulling motion on the rod. This rod pulled a frame mounted lever towards the front of the truck. A shorter rod was also attached to this frame mounted lever that would in turn push the MC. This sounds really complicated, but it is really a simple setup. Many after market frame mounted MC brackets can be made to work with or without a booster. | | | | | Joined: Jun 2012 Posts: 60 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2012 Posts: 60 | Thanks . To simple ,I have a love /hate relationship with acronyms . 
Allan
1946 GMC
1949 Mercury M68
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