Howdy,

Question one;
Were later brake lines larger than the early ones and if so, when were they changed?

Question two;
Was there a change in shoe return spring strength and if so, when?

The problem;
My '62 (with 9"ers) has its original brake lines and I've been wrestling with something new to me. Bear in mind that I've blown through all the lines and the air flow was essentially unimpeded, I've rebuilt or replaced all cylinders including the master and rebuilt all the mechanicals as well. Fresh drums and new shoes comlpete the package. The lines and fittings are all that're still original (the hoses are new of course).
I've owned other toads before and this is the first time I've had this problem, with any car.

Since I've had it the wheel cylinders retract slower than the master cylinder does. This allows the master to back-flow fluid into its cylinder and over fill the system slightly, thus keeping the wheel cylinders too full and the shoes too close to the drums (at times even dragging one for a short period). They always settle back within 5 to 15 seconds.

Naturally I initially figured rust in the lines and a flow rate problem, possibly the wrong shoe return springs (too weak) or possibly the wrong pedal return spring (too strong).
However they are the original equipment, and a dragster I built last year has the very same problem with fresh lines. Now I'm considering a possible marginal design problem and subsequently a re-engineer to larger lines and/or secondary shoe return springs.

Comments?

_________________
Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

TTBOMK, the brake line diameter wasn't changed.
The springs and hardware were upgraded a few times along the lines, though I don't know specifically if the shoe return spring strength was changed. If so, it was a noncritical change, i.e., you can use the later (presumably stronger) springs in an early application. There is a significantly upgraded hardware setup used on the 9" brakes installed on the rear of certain Dakota pickups that works well in the A-body brakes, and you can install the 2nd-generation self-adjusting setup in your '62 (originally w/o self adjusting capability at all); see this post for details.

It sounds to me as if the problem is in your master cylinder. It's new-new, or a rebuilt, or...? It's an original-type single-pot unit, or a dual? Is it equipped with a pressure residual valve behind the brake line seat? If the master cylinder is right for the application, I think it is probably built incorrectly, specifically with the return port too small, partially blocked, or in the wrong place. The problem is not related to the brake pedal return spring (there is no such spring), and it is probably not related to your shoe return springs, though those could be suspect if you wound up with a low-quality hardware kit (easy to get these days even from major names...finest "made in China" quality...)
There is no such problem in the stock system, and larger lines won't help.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Are you sure the relief port in the master cylinder is uncovered all the way? If the brake pedal free play is too low the relief port can be blocked and retain excess pressure in the brake system. I had this happen when I swapped to disc brakes in my '66 Dart.

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Joshua

Thank you gentlemen.

Your information was most helpful in eliminating some of the possible causes my ignorance'd allowed me to consider. No significant changes in the line size or shoe spring strengths did indeed leave the masters. And in that both are cheap remans (from the same supplier) I got in a parts swap it seemed reasonable that they shared a common problem.

That problem turned out to be impeded rearward travel of the piston/cup in the (I prefer single pot) masters of both the Toad and the HAMBster. Both due to excessive resistance in the pedal mechanisms and both failing to fully uncover the relief port from time to time as suggested.

In that I like a bit more overkill than that, after freeing up the two movements I added an external pedal return spring and adjustable pedal return stop to each. The (very thin appearing) return springs inside the masters simply weren't up to the job of pushing the pedals fully back unless everything stayed perfectly free. So now all those inside springs need to return are the pistons/cups, which they manage well enough.

In the case of the Toad I simply cobbled up a heavier duty brake light switch bracket with the pedal return stop on it as well, then added spring end holes to the pedal bar and the hanger lip.
For the Barn Job I only had to add the spring as I'd put in a return stop at the pedal when I designed'er.
Both are working correctly now.
It's nice to be able to adjust the brakes properly at last.

Dan, I'll keep the link and I may someday go to those self-adjusters but for now I quite enjoy the regular upkeep of the Toad. Perhaps when I hit my seventies ........

_________________
Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

Glad to read you got it worked out. Not uncovering the relief port only bit me just the once when I put disc brakes on my '66 Dart. Last weekend I was racing a brand X and the front calipers seized up. Just old calipers though. Opening the bleeder revealed no retained pressure, but vapor did come out!

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Joshua

Dick, my I ask why you prefer the single pot MC? I always ran them, untill a few years ago. I had a completely "NEW" brake system on my Cuda. One day pulling out of my garage to load up to go racing, the pedal went to the floor. Almost hit one of my other cars. The MC was dry. Found both rear wheel cylinders leaking. These cylinders were brand new and only about 6 months old. I was lucky it happened at home, instead of a couple of hours later, at the track, on a 95+ mph pass. Now all my cars have a dual pot MC.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Certainly Charlie,

Most folks disagree with me, but my reasons are pragmatic.
In that I spend far and away the most of my "hard street braking" time in corners rather than straight lines I prefer handling a full brake failure to a partial, mostly due to experience.

Both your illustrations are in straight line travel and the one at low speed. I that respect you are quite right, redundant systems divided fore and aft are usable. In particular the one at the strip is a "best application" for four wheel braked cars.

However, the three street brake failures I've had over the years have all been in cornering.
In the one case that I was driving a dual pot master the rears let go (split a wheel cup) and the car swapped ends nearly instantly, to the detriment of my rear sheet metal and the annoyance of a tree. Had it been the fronts the end results would've been much the same but at the radiator end of the car. Fortunately I was alone on (and off ) the road at that time.
In the other two the whole system let go of course (one ruptured line and one ruptured master cup), and I was able to slide on through it, albeit quite sideways both times, using the gearbox, the wheel and the gas. One of these was in traffic and one between parked cars.
I certainly got the other drivers' and some pedestrians' attention, but didn't have to introduce myself otherwise.

None of the failures were my own wrench work, another lesson I've taken to heart.
Yes, I was over the speed limit in all three cases. I do that. I'd prefer to do it as safely as I might.
Let him who has never ...........

The Barn Job has no front brakes so that one's moot.

_________________
Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

Yikes.

Notwithstanding the "225% crazy" disclaimer in your signature, this rationalisation for preferring single-pot master cylinders is very similar to assertions like "Oh, I don't wear a seatbelt because in a crash it's safer to be thrown clear of the car".

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I don't see how NO brakes is better than SOME brakes. This is an issue that I thought was settled a long time ago... Every pre 1968 automobile I have owned had the two pot master cylinder installed in it (by me). My high school auto mechanics instructor used to say "Brakes, steering, everything else, in that order." I consider a single pot master cylinder a design FLAW in the car! I don't consider trees, people, and other automobiles as part of my braking system!

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Slanted D150

They're not. They're your crumple zone, don'tchyaknow!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I use front only brakes im my mudbogger.....with a dual M/C. One brake is better than none. I send one line to each caliper......car is locked in 4x4 so I actually get 4 wheel braking.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Interesting--do you notice any difference in braking (i.e. pulling left/right). I always understood the front and rear pistons on master cylinders to be different sizes, etc.

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Slanted D150

Most folks disagree with me.

Hasn't changed.

_________________
Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

Ever think there might be a good reason?

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

_________________
Joshua