uprated brakes

[DANJAC2106]

hi all , has any one had much success useing a bigger brake master cylinder off the750i e32 ..ive got no pedal on my special im building which is 325i engine,box propshaft,diff . engine has had all injectors ,and electrics removed and is running megajolt with webber 45,s,which have been a pain upto now ,but does run.
anyway its got std brake master cylinder to tr6 vented discs on the front and the rear fordscorpio solid discs ,(cos i needed that combined handbrake )..in the cockpit ive put a line lock .,simple on|off lever ..heres the problem ...when the lever is open i have very poor pedal ,when the rear is locked off ,the fronts work fine with good solid pedal?,this makes me think the system is not holding enough fluid ,and or ,cylinder diameter needs increasing ?i have no servo,and have bled the brakes 3 times ..i know it sounds like a bodge ,but its meant to look old ,which suits the rest of the car ...all ideas welcome .. thanks Dan

[HairyScreech]

Best thing you can do here is measure the brake caliper pistons and post up the sizes and number of pistons. That way we can make suggestions based on the piston sizes we are dealing with.
As things stand I doubt anyone on here has direct experience with a set up like that.

[keri-WMS]

So this is a scratch build kit car / race car type of thing? Have you got TR6 front struts / calipers / discs?