Disc Brake Conversion Question

[dcramos72]

Yes, bench bleed the MC before installing. Filled to 1/4" below edge and bleed till the fluid was about half way down in each cylinder.

Brake pedal rod long enough? You mean rod coming out back of booster? Currently brake pedal is in its original position when completely out.
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[luvbowties]

Originally Posted by dcramos72

Yes, bench bleed the MC before installing. Filled to 1/4" below edge and bleed till the fluid was about half way down in each cylinder.

Brake pedal rod long enough? You mean rod coming out back of booster? Currently brake pedal is in its original position when completely out.
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Did your kit have a plug (spacer) to put into the hollow end of the mc piston? This hollow may be in the mc piston where booster rod fits--some mc's are hollow here & require that plug for a spacer; other mc's are 'blunt' at this piston surface & do not need the spacer.

[dcramos72]

No plug or spacer came with the kit (just plugs for brake line inlets for bench bleeding). Can't remember if hollow space was blunt or flat.

Can't tell if brakes are applied (sitting in garage), but does not feel like it.
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[luvbowties]

Originally Posted by dcramos72

No plug or spacer came with the kit (just plugs for brake line inlets for bench bleeding). Can't remember if hollow space was blunt or flat.

Can't tell if brakes are applied (sitting in garage), but does not feel like it.
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One of 2 things is probably happening. (1) Your pedal is not pushing fully into the booster . or (2) Your booster is not pushing the mc-piston fully into the mc. Get someone to help you & see what happens when you try to bleed your mc via the leg-pumping method. If it bleeds & builds pressure properly, problem solved. If it merely pumps just a tad of fluid, or maybe none, then one of the 2 scenarios above exists. I'm betting the mc has a hollow piston that will require a spacer. BTW: This spacer can be made from a bolt you cut the threaded end off of--one whose diameter is just enough smaller than the hollow in the mc piston that it freely, but closely, "rattles around" when test-fitting into hollow. Cut off just enough length--approx. 1 inch +/-. Using a bench grinder, dress down one end to a blunt point, or cone, kinda like the end of a .38 bullet. Grind down other end about flat (or indented just a tad if you can drill the end ever so slightly with a big enough bit to make it into a very shallow well-shape: to accept a booster's push-rod), to make the length come about flush with the end of m-c piston's outer limit of travel in the cylinder--you will be filling the hollow. Again, some mc's have a flat-ended piston, against which which the orig. brake-rod pushes; these use no spacers. Others have a hollow piston, **into which the booster-rod enters about 1 inch+/-. **Here's where I feel you are "coming up short".
Did your kit come with a single-outlet, single-line mc like what came on your truck originally? or did it come with a dual-outlet, dual-line mc like comes on '67 and newer, which requires you to re-plumb your system to accept the dual-brake system?

[luvbowties]

One more thing: By drilling a hole 1 inch lower than original hole for brake-rod, it gives the push-rod a longer throw, which means it pushes the push rod further into the booster. It GIVES you a 'mechanical advantage' of distance the rod travels and takes away the advantage you HAD of ease of pushing the rod--pedal becomes harder to push but it flows more brake fluid per pump of the pedal. The mfg of your system had a reason for directing you to drill that hole! But, our method might just suffice. Hope this makes sense.

[dcramos72]

luvbowties,

Thanks so much for all of the info. I just drilled a hole 1" lower on the brake pedal bar and unfortunately no diff.

I think you might be on to something regarding my pedal not pushing completely into the MC. When I was bench bleeding the MC, at the end it got to the point where I could barely push the piston in, so I figured it was fully bled. I would assume if the booster rod was pushing into the MC I would encounter that same resistance, but like I sad it goes right to the floor very easily. I'm gonna call Early Classics as well to see if they know anything about a spacer. Like I said I'm pretty sure the piston I was pushing against was flat with no shape at all, but to bleed it I did have to stick a phillips in to the MC about 1" to contact the piston.

One question. When the motor is running the pedal goes to the floor very easily, but when I turn off the motor there is a bit more resistance in the pedal. Any reason for that?

Also this is a dual MC kit with dual front lines and proportioning valve. There is a thick (rear) line and a thin (front) line coming of the PV. Thick line goes to the rear and thin line breaks off to the calipers. Doesn't seem to be any leaks and I did bleed all wheels after I hooked up the MC.

Thanks!

Dan

[luvbowties]

Originally Posted by dcramos72

luvbowties,

Thanks so much for all of the info. I just drilled a hole 1" lower on the brake pedal bar and unfortunately no diff.

I think you might be on to something regarding my pedal not pushing completely into the MC. When I was bench bleeding the MC, at the end it got to the point where I could barely push the piston in, so I figured it was fully bled. I would assume if the booster rod was pushing into the MC I would encounter that same resistance, but like I sad it goes right to the floor very easily. I'm gonna call Early Classics as well to see if they know anything about a spacer. Like I said I'm pretty sure the piston I was pushing against was flat with no shape at all, but to bleed it I did have to stick a phillips in to the MC about 1" to contact the piston.

One question. When the motor is running the pedal goes to the floor very easily, but when I turn off the motor there is a bit more resistance in the pedal. Any reason for that?

Also this is a dual MC kit with dual front lines and proportioning valve. There is a thick (rear) line and a thin (front) line coming of the PV. Thick line goes to the rear and thin line breaks off to the calipers. Doesn't seem to be any leaks and I did bleed all wheels after I hooked up the MC.

Thanks!

Dan

((One question. When the motor is running the pedal goes to the floor very easily, but when I turn off the motor there is a bit more resistance in the pedal. Any reason for that?))...That is good: it shows your booster is 'boosting' and making it easier to depress the brake pedal while running, which is the correct thing for it to do.

I still think the little spacer is going to be the solution. I read about some 'Corvette-style' mc's last nite, & the site mentioned it included an 'adapter' for the different style mc.

This site mentions the different mc's, the deep-hole and the shallow-hole. Don't see the site mentioning including the adapter right now(gotta go meet my walking buddies).
>> http://www.tuffstuffperformance.com/...cat/cat210.htm <<