Master cylinder conversion

[V8 Bob]

V8 Bob, did you have clearance problems with the F250 MC in your 40? I used a 69 mustang in mine and had to cut the cover and weld flat. Otherwise is too tight to the floor and cannot remove the lid/cover.....

I had to make a slight "hump" in the new/larger M/C cover to clear, but it's not really noticeable under the carpet.

....If the master cylinder bore is to small, is it possible that it will work "fine" with both circuits operating as they should, but in a one circuit fail, the master cylinder can't displace enough fluid to operate the one circuit now doing all the work. Irrespective of the ability to full stroke?.......

Martin, the two circuits are isolated, and only operate two brakes each. The 1" master is the most common size, and generally will work with most car/light truck/street/hot rod brake systems, but they do vary on total and primary/secondary displacement, or individual stroke, depending on intended application. However, checking each circuit for operation and pedal reserve during bleeding will show if there is a fluid displacement problem.
Generally, brake pedal force on factory vehicles is somewhat controlled by public feedback, but mostly DOT maximums allowed during required testing the vehicles have to adhere to, and is a good guide when building a custom system.

 

[FlatheadTed]

Bobs explanation 0f how each circuit is independent is how I always believed it worked on a duel M/C .I recently did a conversion from a single M/C to a duel type ,went from !" down to 7/8 M/C .I had a lot of pedal travel and was about to go to a bigger M/C but decided to re bleed them ,the bleeder was one were you couldn't get a hose on it and could easily trap air so I gave the longest one (left rear wheel ) a another good bleed and suddenly I got a good pedal .On a drum system I suggest soft lining on the front if you are not using a Vac booster .Ted

 

[flatford8]

Tons of good info here relative to my upcoming projects!!!!... Thanks to all who shared/posted.....MARK

 

[scooder]

Thank you for your reply Bob.
Martin.

 

[HemiDeuce]

Here are a couple of 1 /16" Bore Wagner Master Cylinder numbers for those that might be interested in a dual bore master cylinder.
Your parts store can probably cross them to the make that they carry, if they don't have Wagner available.
MC 97936, 1/2-20, & 9/16-18 outlets on the right side.
MC 97938, 3/8-24, & 7/16-24 '' '' '' ''
MC 102420, 1/2-20, & 9/16-18 outlets on the left side.
MC 102421, 3/8-24, & 7/16-24 '' '' '' ''
These are slightly taller than the popular Ford master cylinders, so check your space available.

 

[hotrodA]

Thanks, HemiDeuce, for the "meat and potatoes". Real pertinent info.

 

[flatheadfan]

Rock auto has several of these m/c at a great price:

http://www.rockauto.com/catalog/x,carcode,1123399,parttype,1836

Tom

 

[Richard (EV8G)]

I tried a stock early Ford single master cylinder. It was 1 1/8 or 1/16. The pedal required too much force. When I went to 1" the brakes responded much better. This was in a model A and the pedal arm ratio may be different on other cars. I have not tried a simulated failure of one circuit. That is really a good idea.

Richard Lacy uses 15/16" in his kits.

John

We use a 7/8" MC on our 1932 kit BECAUSE of the over-all pedal ratio resulting from our design. We use 1-1/16" on 33-34, 35-36 and 37-38 kits. If we install a "dual" MC on 33-34 we are stuck with a 1" which is not ideal due to the increased pedal travel required. We do have one with built-in RPV's and LH outlets.

 

[al pa.]

My problem was that after installing dual mc,using the inboard ports,I found that the exhaust was too close to the brake lines.I fabricated an exhaust section that turned down from the header,turned towards the rear,below botton flange of the frame,then gradually back up to the muffler.M.C.had ports on both sides,I should have used outboard ports.Didn't want to redo brake lines.