Started replacing my MC as well as the rear flex line and wheel cylinders today and so far haven’t broken anything.
Putting the MC in was going great (and I even “bench bled” it) and then I cleaned up the fitting on the steel line so got a really good look at it while making it move easily for the mating to the MC.
That’s where I stopped because the hole in my new MC is almost 3/4” deep to get to the bevel inside but my old one is just shy if a 1/4” deep. I’m thinking I need to either cut off the tip of the steel line and add a longer fitting and then flare the tip or get a different steel line which may mean buying a whole kit. I usually get stuff from “Chevy’s of the 40’s” because they are in Washington and so am I.
Anyone know if this fitting to the MC is supposed to be longer than all of the others?
1951 GMC with positive ground. Engine is a ‘54 Chevy passenger car (Serial Number 0024472F54Z) with a ‘56 head (casting code on top of head 3836848 GM 4), Casting Code (on passenger side on side of head B56 848 850)
Do you recall where you got the replacement MC from? Brand/Part Number?
It might be all you need is a brass adapter fitting, but can't say more with out a little more details on the stuff you have.
Pictures would be helpful.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
The inverted flare nuts are available in at least 2 lengths, you first need to know what the line diameter is, typically 3/16", 1/4", 5/16". that diameter will dictate the flare nut size and the SAE thread size. Stop at your FLAPS and buy a couple of new long nuts.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
Some replacement MC's use a brass banjo fitting secured by a hollow-drilled straight thread bolt instead of an inverted flare fitting. Better check the bottom of the M/C thread to see if it has the necessary inverted flare cone to seal a piece of double flared brake line tubing. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Ok here is a photo of the new and old master cylinder. Are you saying the end unscrews and I’ll be able to take out a extension piece inside?
Last edited by klhansen; 05/31/20263:07 AM. Reason: Fixed image display
1951 GMC with positive ground. Engine is a ‘54 Chevy passenger car (Serial Number 0024472F54Z) with a ‘56 head (casting code on top of head 3836848 GM 4), Casting Code (on passenger side on side of head B56 848 850)
There is no brand name on the new MC just a number cast into the body (B238) and I got it from “Chevys of the 40’s in Vancouver Washington.
1951 GMC with positive ground. Engine is a ‘54 Chevy passenger car (Serial Number 0024472F54Z) with a ‘56 head (casting code on top of head 3836848 GM 4), Casting Code (on passenger side on side of head B56 848 850)
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I see what you’re saying, Jerry, but the old one didn’t have that banjo and it looks like the inside of the old one may have an insert.
I tried what I had in my shop but the fittings were too small for both the old and new. Then I tried the new rear flex line just to see if the threads fit and it threads into the old MC but is too small for the new MC. So no matter what the fitting on the existing steel line isn’t going to fit the new MC.
I’m going to take it down to Napa on Monday to see what size it actually is and if they can get an insert/extension. Plus I’ll call Chevy’s of the 40’s.
Meanwhile, since the truck is stuck on my lift, I’ll see if the rear wheel cylinders fit because they DO have banjo bolts on them.
I’ll be back to close the loop next week…
1951 GMC with positive ground. Engine is a ‘54 Chevy passenger car (Serial Number 0024472F54Z) with a ‘56 head (casting code on top of head 3836848 GM 4), Casting Code (on passenger side on side of head B56 848 850)
To my knowledge the end caps are not switchable between your original and the repop MC. I went through this same issue when I had to replace my '51 Chevy 3100 MC and my original end cap and line fitting was the same as yours pictured.
After trying 3 different Classic Parts '51 specific MC's (with all 3 failing internally out of the box) they replaced the non-working '51 style unit with a '52-'55.1 MC to which they added a brass adapter fitting to work with the newer sized output plug on the MC to connect with the original brake line fitting. Classic's pictures don't show the fitting or a good view of the output port, but Jim Carter's offered 1952-55.1 1/2 ton MC pictures the same "B238" casting number on the MC and the brass adapter fitting that he provides with his.
I have a spare '52 style MC that came with the adapater squirreled away somewhere that I got from fellow Bolter Phil "Phak1" some time ago. If I can dig it out, I can try and get the measurements/thread count from the fitting and post so you can try and locate one.
Alternately, you could reach out to Jim Carter and see if they can provide the adapter info.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Those concentric grooves on your new cylinder's end cap are obviously intended to engage a copper sealing ring that's used with a banjo fitting. I'll bet the threads are straight, intended for a 1/2" or maybe a 9/16" banjo bolt. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
I was able to get a reducer fitting with a copper washer from a brake and clutch specialty shop in Seattle. Now I can just attach my existing quarter inch hardline with 7/16 fittings.. this is the one hardline that is actually in great condition because it goes under the transmission and was coated with grease and dirt to keep away rust. I’m making new lines for all the other hardlines and the copper/nickle 3/16 rolls of hardline are so easy to bend and form!
Last edited by 51 Jimmy; 06/09/20264:38 PM.
1951 GMC with positive ground. Engine is a ‘54 Chevy passenger car (Serial Number 0024472F54Z) with a ‘56 head (casting code on top of head 3836848 GM 4), Casting Code (on passenger side on side of head B56 848 850)
Glad you got it sorted out. Keep us posted on how the rest of the brake work goes.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Brake lines can fail from internal rust, so the fact that the outside looks good is not necessarily reassuring. DOT 3 brake fluid absorbs moisture. On the short term this is good as it keeps a small amount of water in suspension. Long term, it will rust the line.
Since you are this far into the project, why don't you assure your safety by replacing this one line?
