Mk2 escort brake bias box issues

[Mike Ryan 8878]

I have recently completed my long time build of a mk2 escort van. With the engine I fitted it was necessary to fit a brake bias pedal box. I am having issues with getting any brakes though. I have 9 inch drums with larger cylinders on the rear. The front is a set of 4pot princess copy calipers. On vented discs. Initially I had no pedal. Then after alot of messing I managed to get brakes but only on the rear. After some more research I swapped the cylinder sizes to0.7 for the rear and 0.75 on the front. This did give me braking but the pedal is at the floor. I swapped them around this weekend and it resulted in no brakes again. The rod on the front is about twice the legnth of the rear to try and keep the balance bar perpendicular to the cylinders. I am sure the problem lies with the front as when I clamp off the flexi hoses the pedal is stiff as you would expect. Can anyone suggest what to try as this is doing my nut in now. I have tried bigger and smaller cylinders but can't seem to get enough fluid through to the front calipers. Can anyone give advice on their set ups or experience. Cheers Mike

[stevieturbo]

So you are saying you have no fluid at all to the front brakes ? You can't bleed or do anything ?

Yet you seem to say when you clamp the flexis the pedal is hard, which would suggest there is fluid there and it is bled ?

So which is it ?

When you press the brake pedal, do the pistons move on the front calipers ? Where you able to bleed fluid through ? Is there no force at all to stop the disc rotating ?

[Smint]

A couple of thoughts, probably miles off.

1. schoolboy stuff, the bleed nipples are at the top of the calipers?

2. I recall decades ago having hells own job getting Series Landrover drum all round brakes to bleed, after hours and pints of brake fluid doing no good i G clamped the slave cylinders fully closed (could wire them closed too), the same could be done with the calipers, 5 minutes later had the worlds best LR brake pedal.

[Mike Ryan 8878]

I do get fluid to the front calipers and they do brake but the pedal is almost at the floor. I have tried a smaller bore master cylinder which is what is suggested but I can't get any front brakes then. Yes I have thoroughly bled the system. I have had the eezi bleed on it to be sure. There are 4 bleed nipples on the princess calipers and I have made sure there is zero air in the system. It seems to be a problem with the amount of fluid I can get to the calipers. I have read that other people have used the same setup as me and get a solid pedal at the top. I cannot even get it half way down the pedal stroke. Was wondering if anyone has had similar problems. I have not reinvented the wheel it's a tried and tested setup used on loads of ford's but I am wondering what I am doing wrong in my case.

[shtu]

I'm fairly sure both your cylinders are too small for those calipers.

Have a read of the sizing section of this,
https://www.rallydesign.co.uk/pdf/designing_4_pot_...

A lot of the "sizing" stuff you read on the internet is for using combined master cylinders off other vehicles, which are quite different from the 2 single masters plus balance bar setup you're using.