Front disc brake conversion

From my own experience chasing brake kits. Check the pressure at the master. Then at every wheel. I’ve seen brakes not working both because the pressure is low and that the volume is low. If you can’t get enough volume before it bottoms out you’ll never get the pressure up. I also had one kit with hard pads in front. Plenty of pressure, but not enough friction. Once we went to appropriate softer pads, we could lock the front.

Unfortunately, just because it’s new, doesn’t mean it’s right.


I put “racing” pads on a vette once. About the 3rd hard stop they got warm enough to work. Not so good for that first panic stop on the street.
 
I think the problem(s) is a bunch of mismatched parts.

If the car was OEM manual brakes, a power change-over would not be that difficult.

You have to consider pedal stroke, pedal ratio, and booster to MC rod adj especially if they came assembled.

A 7-inch dual diaphragm booster isn't going to cut it on a heavy MERC (not enough line pressure). They most likely suggested the 7-inch booster to easily clear the FYB exh manifold.

If the kit used GM D154 METRIC CALIPERS (SGL PISTON) they are low drag and require a step bore MC (volume to properly actuate the caliper pistons). Most kit vendors use a CORVETTE MC to make that happen.

Until we get all of the kit(s) info, it is just a guessing game.

I am sure you are aware of all my past b!tchin and moaning regarding these so called brake kit vendors.

And nothing has been said about proper valving.
 
For this example, we would focus the customer towards a 9” dual diaphragm booster (p/n: BM17875-1 or 2). This would include a master cylinder of either a 1” bore or a 1-1/8” bore depending on what had been chosen for the calipers (we will discuss this in another post).

We would choose this option as the 9” dual has as much potential assist as any booster we provide and because the customer is using a SBC engine, there is plenty of room available. If the customer were using a BBC for an engine, we might be forced to drop back an 8” dual diaphragm booster.

Why you ask? The simple answer is room. You may want to use a larger booster but some applications only provide a certain amount of room. Therefore, we put as much booster in the space we have available.
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EXCERPT SOURCE - https://mpbrakes.com/choosing-the-right-booster-for-your-ride/

BOOSTER-MC COMBINATION - DUAL DIAPH 9-inch 1952-56 - MERC​
 

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Single GM calipers , sold with kit, yes it cleared the manifold but not by much. Kit came with Chev proportioning valve and we installed a 10 pound residual valve in rear line, we are going to makeup a pressure gauge to see what master cylinder is putting out, we have tried two mc with no difference in braking and a 7 inch single booster with the same braking. Also drilled hole in pedal one inch lower, no difference.
 
Maybe save yourself some time and effort -


The caliper style is most likely the main part of the problem, that and booster size.

Those calipers are off-shore sloppy copies and take a special MC to energize properly.

Anyone else wanting to retrofit consider the K-4 4-PISTON design. Much better results.

Are the rotor lug nut size pattern 5 X 4.5in or 5 X 5in?

THANX for keeping the board informed as to results.
 
Thanks for all the help, neighbor says brakes are working a lot better, still got things to work out but car show season is over.
 
Thanks for all the help , neighbor says brakes are working much better, still not perfect. Car will be stored for winter
 
Thanks for all your help and great info KULTULZ, I replied twice because I didn't see my first post not realizing we had gone to page two, should keep my eyes open in future. He bought two complete kits, the other for a 56 Ford Fairlane that he says we are not installing as the first was such a disappointment.
 
Again, you are more than welcome.

These GM kits are cheaper to put together, especially when sourcing off-shore parts.

The SGL PISTON GM CALIPERS (METRIC D154) are a low drag design (which is good) but require a dedicated step-bore MC which is hard to duplicate for different kits.

They are also a floating caliper design which is cheaper (for the car manufacturer) to build and less effective than opposing pistons fixed calipers.

That is why the kits come through with a CORVETTE style MC, more volume and needed line pressure (for the calipers)

Every car is different and there is no one-fits-all kit. Each has to be massaged.

Can he return the kit for the FORD?

If not, it can still be used as the TREADLE-VAC
system as used on LINC-MERC has the pedal linkage geometry problem(s).

BOOSTER and MC sizing and correct pedal ratio is important to get right. Gauge(s) will give you that

The truth is in using the 4-PISTON K-H design kits (think copy 1967 FAIRLANE).
 
Here is a descriptive thread one posted (on another FORUM - H.A.M.bone in this instance) going from 1954 LINC CAPRI TREADLE-VAC to a diaphragm booster.


The kit he bought was a 7in SINGLE DIAPH w a four wheel drum SGL RESERVOIR MC (no bore/piston size given), so he must not have wanted to go to front disc or split hydraulics.

It shows in detail how he went about modifying the pedal linkages.

He states it stops fine.

Why upgrade ($$$) if the OEM TREADLE-VAC gives the same results unless it needed an expensive overhaul?
 
My 58 Edsel Pacer had the Treadle-vac system. Had it rebuilt, installed, worked great. Had to park the car for about 8 months due to a big (EBP) prostate issue. Went back to playing with cars brakes did not work! Very hard pedal, very poor stopping power. Made a bracket to mount a dual 7" booster to the original treadle-vac mount and was back in happy land. The master was a 65 Bird. The original brake assembly worked just fine.
 

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THANX! for the info ...

Now did the booster go to the original TREADLE-VAC pedal linkage or did you fabricate some way to use the diaphragm booster on the original TREADLE-VAC linkage (didn't have to go with manual pedal assy)?

No dualing reservoir?

Any idea of final line pressure?
 
...just a minute here ...​

I just realized you have a 58 PACER. Maybe you can answer a question for me as I am too cheap to buy an EDSEL WSM or MPC to answer for myself..

Yours came thru with a 361CI FE (E-400), correct?

Can you tell me if the 361 came through with solids or hydraulic tappets and if hydraulic did it (yours) have adjustable or non-adjustable rocker arms?

What carb and trans did they use?

BTW - I thought guys joined the NAVY 'TO RIDE THE WAVES' ...

Why prostate problems?
 
Yes, it was a 361, the carb was an Autolite 1200, the transmission was the ol 3 speed with the center of the steering wheel push buttons. Which still worked. It had hydraulics and non adjustable rockers.

I figured out that the stock linkage would work...but...mounting the booster was the issue. The stock fire wall mount for the Tredle-Vac can be seen in pic 2, the adapter I made can be seen in pic 3. I also made the push rod to tie it all together. A 8" hit the valve cover so in came the dual 7". The 65 Bird master just happened to have the same bore as the Edsel unit so it won.

The prostate issue was a benign enlarged prostate when I was 72. The only symptoms I had was leakage from time to time and when the urge to pee came it was RIGHT NOW or there would be an issue. My routine check up at the VA turned up an extremely high creatinine count (5.7) (they begin dialysis at 6.0). So in I went for 3 days, tube up little willy, bag and tones of water to see if the kidneys would come back to life. They did, my levels have been a steady 1.7 - 1.8 since. Had the rotor rutter job done, he checked everything for cancer and found none. So we are a happy almost 80 now!
 
I figured out that the stock linkage would work...but...mounting the booster was the issue. The stock fire wall mount for the Tredle-Vac can be seen in pic 2, the adapter I made can be seen in pic 3. I also made the push rod to tie it all together. A 8" hit the valve cover so in came the dual 7". The 65 Bird master just happened to have the same bore as the Edsel unit so it won.
Click to expand...

THANX for that!

So let me get this right ...

You were able to use an aftermarket booster without modifying the pedal linkage setup?

Did you take any more detailed photos?

Did you go to front disc with the conversion or did you stay drum/drum? And the 12in DUAL DIAPH operates the brakes OK (drum/drum)?

The reason I ask is the 65 BIRD MC is a SGL RESVR DISC/DRUM design.

Now for my contribution of "AS THE STOMACH TURNS' ...

Mine began approx 1980. I had caught a very serious malady of 'DIESEL FEVE' in 1974 and was trucking OTR.

Got to HOUSTON one morning and I felt as though I had developed a very extreme case of the G.I TROTS (after another round of 'THE LOCAL TRUCK STOP CHOKE AND PUKE PLATTER) ..

I had my co-driver handle the dock work while I endured the LATRINE BOOGIE. No relief.

Called in and I had him drop me off at a local ER where I was diagnosed with the old prostate malady. I think it was mainly as a result of all those years trucking.

The ER M.D. (she) said the cause was usually too much or too little sexual activity.

It surely was not from too much I guarantee you. I couldn't get lucky if I was a WARDEN in an all female prison with a pocket full of pardons.

So I have fought it since. I am now 78 and my little soldier will not only not come to fill attention but also will not salute ... :(
 
Old age is interesting? No more pics, when the Edsel was modified I was not good at taking pictures. This digital stuff is relatively new to me despite being an electronic engineer!

Yes, the 7" dual diaphragm worked perfect using the stock pedal assembly. The linkage from the pedal jumble was the easy part. No cutting, drilling or welding of the pedal assembly was required. The little adapter to mount the booster to the fire wall took a little "six pack" engineering! The original booster mounted to the fire wall by being bolted to the "dog dish" thing that is bolted through the fire wall to the pedal assembly. After a couple of tries the flat plate bolted to the booster then bolted to the dog dish solved the problem.

The 65 Bird master is a single output, Ford used an in-line regulator to manage the disc/drum set up in that model year. The regulator was I believe a KH unit and it was mounted on the rear side of the drivers side inner fender well just below the master. The bore was the thing I was after. Yes, it was a drum/drum on the Edsel.
 
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