Manual brake MC sizing and pressures

[Skip FIx]

So the first attempted track outing last month on the 500" Pontiac motor/Camaro the Strange /Mopar MC just would not get enough hold for the line lock to hold the car for a burn out. Crappy track we left after two 1/8 passes. Also brakes did not slow the car as much as I would have liked at the top end, 102 in the 1/8th with a SLOW 60 ft, but brakes probably not completely bedded in yet also.

It always took a lot of leg pressure to build pressure max pressure on front and rear gauges after master were maybe 700psi. The MC was a 1 1/8" I had bought years ago. Swapped on a Mopar style 21mm(7/8"), stayed Mopar style as the pushrod and Heim I had set up for the other one. Wow it can make 1100psi with the same leg pressure! It does have a moderate amount of increased travel. I'm going to give this one a try next outing(if it ever stops raining) if the travel is just too much there is a 24mm(about .94") I'll try.

So getting the correct MC size can make a big difference. Many of the manual GM disc/drum cars used a 1"MC, I know Baer even hasa GM style 15/16" it uses for many of it's setups. My 64 has a later Impala dual reservoir manual 1" MC with a moderate deep pushrod recess I am trying on it as more room around the valve covers without a power booster.

 

[1958 delivery]

Why would you ever try a 1 1/8" master for manual brakes?

 

[1964SuperStocker]

I went with the small 7inch dual power booster to give me as much room as humanly possible.

 

[jdk971]

i believe my vette came with a 1 1/8 master. with drums. jim

 

[1958 delivery]

i believe my vette came with a 1 1/8 master. with drums. jim

no it didn't

 

[Skip FIx]

Why would you ever try a 1 1/8" master for manual brakes?

I had it and in the Strange Catalog they recommend it for 4WD. And 4 pistons may end up on the rear and the current rear has more piston sq in that 4 piston Dynalites

"Application
Vehicles with front and rear manual disc brakes
Normally used with four piston calipers in both the front and rear brakes "

 

[1958 delivery]

You have to have lots of surface area from multiple or big pistons to use 1 1/8" for manual. The common app is on some big trucks that have 3.25" pistons up front. Not a normal car situation.

 

[1958 delivery]

So what kind of "racing" is this that you would have multiple calipers per wheel?

 

[Skip FIx]

Wilwood Dynalites have 4 pistons per caliper and are in most of their disc brake kits. But yes a little big MC for these. I thought since the rear metric has a little bigger piston it might be worth a try but nope.

 

[1958 delivery]

Dynalites have tiny pistons. I thought you had said that you have some kind of multiple caliper set up. Also a rigid mount caliper you don't count all the pistons different then a floater.

 

[Skip FIx]

Nope just 4 1.75" piston Dynalites on front and the 2.5s on the back.

I have a dual circle track type pressure gauge plumbed before the LineLok and before the adjustable rear prop valve.

 

[jdk971]

was it 7/8 then? jim

 

[Skip FIx]

Yes 21mm close enough to 7/8.

 

[1958 delivery]

I never heard of Texans speaking "mm"

 

[Skip FIx]

Well you know these late 70s speak 2 different "languages" EU and English And heck it IS a Mopar MC!

 

[Skip FIx]

One friend did saw instead of swapping another one in if I do not like the feel of this one try swapping the rod to the lower hole to get less travel, but will have a little less leverage.