Technical 1954 Lincoln Brake Swap Question

Newbie here to this board, but a long time reader. As title states, I have a question (scroll down if you wanna just read the problem), more of a concern really, about a Treadle Vac to conventional master cylinder/booster swap. Car is a '54 Lincoln Cosmopolitan (Capri badging), swapped the tired and somewhat working Treadle Vac with a Jamco Suspension 52-54 Lincoln brake conversion kit. After some finagling, I got the new kit bolted up and linkages all fit.

The issue:
The pedal travel is 1-1/2", maybe 2". I confirmed that MC pushrod seems to be doing full travel, just the pedal feel and travel is abysmal. All the underdash brake stuff is factory, I used as many factory components as I could. As for the kit, I simply removed the supplied threaded rod and linkage and instead used a threaded spacer to connect with factory linkage.

Will add pics tomorrow if I am able but has anyone had any luck or similar issues using Jamco's kit? Do I live with the reduced pedal travel? Has to be better still, and safer, than the Treadle Vac setup, right?

Thanks to all in advance for your help

 

So decided to continue with the Jamco kit. I am suspecting this kit was intended for manual brake cars, which the site doesn't mention. Just trying to get the car to be able to drive and stop for now, will sort thru the details later.

For anyone looking to use this kit, not a bad install, will need to find a way to adapt the factory linkage to the Jamco setup. The bracket raises and pushes the booster/mc forward, so plenty of clearance. As mentioned the pedal travel and feel suffers.

 

I can’t comment on your specific kit. But there’s 2 pushrods there, if it’s a typically set up. One from the pedal to the booster, and one from the booster to the master cylinder. At least some m/c I’ve had came with a spacer. IIRC, the spacer was used when mounting to a booster (shorter pushrod) and left out if manual brakes. Whatever the reason, if you’ve got full travel from pedal to booster, but lacking travel (missing spacer, etc) from booster to m/c, you’ll get weird symptoms and bad brakes. If it came assembled you might check.

I’ve only worked on the Treadles on a 56 Chev, and the linkage there was a whole different animal than most modern units. Not a clue about your Capri.

First car I really remember was a 54 Capri Dad bought in 55. I still have to stop and look whenever I walk by one.

 

It sounds like there isn't enough pedal ratio. is the pedal hard too? and is the booster working?

 

Found on another deal that the pedal ratio on a treadle vac set-up is too low for a modern booster. Fellow ended up removing the OEM pedal set up and replaced it a universal aftermarket pedal assy. Worked good then.

 

Easiest thing to check first is the booster-to-master pushrod clearance. There should be no more than .020" gap between them. If there is, you can unscrew the booster pushrod to close the gap. Too much gap leads to a long pedal travel and a mushy feel.
The best way to measure is to buy or make a tool like this one:

 

What did (or does) JAMCO have to say? Was the INSTRUCTION SHEET not clear and/or confusing? They surely have a TECH LINE.

The only advantage I could see with replacing a TREADLE-VAC application is the cost involved overhauling the TREADLE-VAC and the ability to use a dual reservoir MC and optional DISC BRAKE upgrade.

Is the car four wheel drum and did they give you the correct MC?

Can you post the KIT # you bought?

It seems the problem (IMO) is incorrect pedal push-rod length as the BOOSTER to MC rod travel is usually set to spec by the kit vendor if the components came assembled.

 

If you look at the above parts drawing and look at how the pedal works with the intermediate pivot arm you can get an idea on how there is a very low pedal ratio using the treadle vac linkage.

This results in short travel and high effort pedal when hooked to a modern booster & master.

Treadle vacs and their pedal linkage are a matched system.

 

Now was this on an OEM install or an earlier car fabrication?

I wish the OP would answer my questions above as if one of these so called 'BRAKE KIT VENDORS' is selling a diaphram vacuum replacement, they should indicate clearly if the conversion will work with the OEM linkages or if modification(s) need to be made.

 

I don't remember the car; but looked back in some convo's and it was a '50s Buick. An aftermarket booster and dual master had been installed in place of a treadle vac at a "shop".

The guy was having the same problem, very little pedal travel and he had to stand on the pedal.

We have a library in town with many early factory service manuals and I found a picture of the pedal linkage, using the drawing and measurements the guy got of the actual pieces, we determined there was hardly any leverage added. The pedal linkage had intermediate levers (bell cranks) kinda like the picture @KULTULZ posted. Buick shop manual said 1-1/2 to 1 pedal ratio for the treadle vac and 6-1 for the manual brake assy.

He found a manual brake pedal assembly to install and fix the problem.

I had deleted all my related pictures and notes; but found a couple in a message of the two pedal assy's that show the differences in the pedals and bell cranks and the resulting changes in mechanical advantage.

 

... hmmph ...

I appreciate the comeback.

Now only if I knew what the kit vendor recommends. Strange it wasn't brought up.

EDIT-

Actually, the OP brought it up -

 

I found this disclaimer on a number of sites. It is akin to the ADJ PPV. They say to use it but on another page says it is not to be used on the street or to replace any OEM valve. It covers their butt if you bust yours.

So what is happening is there is no direct diaphram booster/booster-MC changeover for a TREADLE-VAC. They (kits) are sold as universal and they will recommend what they think will work on your vehicle. Linkage(s) have to be setup by the vehicle owner.

Now, one would have to go to a MANUAL BRAKE SYSTEM LINKAGE/PEDAL ASSY for the particular model TREADLE-VAC equipped car and then go from there as to pedal ratio and actuating rod length.

I guess this 3rd Grade edumication (two years) I finally attained leaves a little to be desired ...

I am old and tired and thought I had gotten over a$$-u-me.

THANX! for everyone's input ...