I have the Touring Classics c5 setup on the front and the LT1 brakes on the rear. It came with a 1 inch master cylinder and the pedal effort was too high. I picked up a master cylinder for a 77 Malibu Cardone# 101639. I was under the impression this was a smaller bore but the bore where the pushrod goes in measures 1 inch on both of them. Is this the same cylinder or does the bore size neck down to a smaller size inside. Any way to measure this without taking it apart and having to rebuild it?

I measured 2 MC's I have on the bench, I didn't remove the cyl from the bore. I measured just along where the clip ring goes...

1> Old power disc/drum MC that I assume to be 1 1/8" (1.125) bore. It measures at 1.147"

2> Un-used CPP power disc/disc that I bought as a 1" bore. It measures 1.111"...

How are you plumbed from the MC to the hard lines feeding the front and back? I have the same TC front and rear and although the pedal is not like power I find it very much like a manual 4-whl disc Vette I drove years ago. I've pondered going power or Hydra-Boost but was out for several hrs earlier today and was wondering why I was even thinking about it... To me a little harder pedal isn't bad as long as you are getting good braking for less pedal movement. If I ever felt I had to use 2 feet to stop the car that would be another story... If you have always driven power brakes it is an eye opener the 1st time you drive manual brakes...

I am using the stock manual brake lines that were on the car. I am using a 1/4 line on the front that does into a 3/16 tee. The back lines are 1/4 into a 3/16 Jegs porportional valve. The cars stops ok but I think I should have some more. The pedal has about 2 inches of travel and then is very hard. It is impossible to lock up either end, which makes me think I should have some more stopping power available. Maybe I am wrong. First exerience with manual brakes. The firm pedal does not bother me so much as the inability to lock up any wheel. I would think I should have enough stopping power to do that. Am I wrong?

Hi Keith, you should indeed be able to lock the tires... Set your prop valve so you are not restricting the pressure to the rear you should be able to lock the rear real easy. I base that on my setup which is almost identical. If you can't something is amis. Did you swap holes in the firewall for the clevis pin?

I couldn't lock the fronts but I was running a bad stock disc/drum dist block and the problem followed from stock 11" to 13" setup. I replaced it with a T for the front and direct to the prop valve in the rear and solved that.

Keith I have also found MC's with 7/8" bores for more pressure with less effort but you get more pedal travel in return. Although most guys I talk to use 1" for manual and 1 1/8" for power set ups.

Factory 4 wheel disc corvettes from late sixties to mid 70's used a 1" bore M/C for manual and 1 1/8 for power brakes.

I have the 1" manual with a dual diaphram booster and pedal effort is certainly much easier with the car running. I realize that my pedal attaches at a different point due to the power brakes but you could always add a booster to your current set up if pedal effort is an issue.

My car is a 4 wheel disk car with the rear discs from touring classics.

I have the prop valve wide open to the rear. I have also replaced the stock distribution block with a tee. Could my stock lines be too small? Do brake pedals vary from one model to the next? I have no idea what model the pedals came out of. Ebay purchase. Do the leverage ratios vary? I prefer to stay manual. Any idea on how the figure out the size of the master cylinder without taking it apart?

Depending on the popularity of the one you got and if it was made new or remaned from factory parts you might be able to determine what it is with a casting number.

Your lines are likely not to small. Later model calipers use less volume and higher line pressure so line size shouldn't be an issue for the fronts certainly. I've heard of some guys downsizing the front to rear line from 1/4 to 3/16.

I've only got ~300 miles on my set up so I haven't tried any threshold braking yet so not sure if mine will lock but it feels like they should and I'm running factory sized lines.

Keith - My lines are factory drum lines front and rear. I made my own lines from the T across the axle tubes to the braided lines in the rear. I figure we have the same MC, supplied from TC - it's a 1" bore disc/disc unit.

I would go back over everything, was the MC bench bled properly? Lines bled properly from there? Your pedel might make a lot of difference, if the cleaves pin was shorten right and placed in the right hole on the pedel (I think I said firewall earlier, that was my brain transposing what I typed wrong) no problem. If the pedel was wrong maybe the hole for the pin is in the wrong place...

A 1" MC should work okay with those brakes,albeit with more than average pedal pressure necessary. Make sure you have the pushrod in the manual brake hole in the pedal (the upper one). It makes the travel longer but gives you more leverage. The size of the lines makes no difference whatsoever. This from Carl Bush, Wilwood`s Sr. tech instructor. They plumb race cars with all 3/16" line. If the 1" MC still isn`t working for you you can either go to a 15/16 or 7/8 bore MC which will make the pedal effort less (easier to lock them up with equal foot pressure) and the stroke even longer, lengthen the pedal (which won`t make it much better without making it stupid long),or go to power brakes. There are reasons they never made C5s or 4th Gen F bodys with manual brakes. ;) Mark SC&C

Well, I got bored tonight and took the new malibu master cylinder apart and measured the bore. 1 inch. I took the 1 inch master I had apart and guess what. 1 inch. Now I have two 1 inch master cylinders and I can not find the receipt for the one I just bought. Gotta love it. What are you guys running for pads? I am running the stock pads that come with the kit. Would a change of pads help? I hate to keep buying 15/16 master cylinders and getting 1 inch. Any suggestions?

Keith - not to be pressing but you seem to be avoiding the brake pedal. Do you know for sure it's right for your car and if so is the clevis and pin mounted in the right hole?

That's messed up. The cardone 101639 is listed as 15/16. It also has the ports reversed from the typical 1" available. and says it comes with a pushrod. I was thinking of getting one sometime just to check it out, but maybe i wont.

The pedal does have a bit to do with it. The correct pedal has a 6.25:1 ratio. If you got one with a 5.5:1 it could significantly increase your foot pressure needed on a C5 system, but with enough foot pressure they should lock.

what pedal system are you using? I hope it's at least 6:1 with those brakes.

I checked the pedal again last night. The pushrod is in the upper hole. The upper hole is in the same position as the hole for the clutch pedal. It looks like the hole is straight across from the pushrod hole in the master cylinder. Has anyone ever drilled a new hole higher up? I have plenty of pedal travel to use, but it only moves about 2-3 inches now. Maybe I am just being picky because it does stop and I love the feel but the lack of being able to lock them up tells me I may be missing out on some braking power. This is intended to be an autocross and track day car in the future.

How do I calculate the pedal ratio. What do I measure from where? Also the 101639 I got has the ports on the same side as the 1 inch master I already have. I think that is off a corvette. After tearing them both apart last night the internals of the 1 inch are of considerable better quality the the 101639 I got.

Your calipers have smaller bores than original Camaro brakes, so don't worry about what came stock.
I tried manual brakes on a Baer 13" C4 type system, it's a second gen with the same pedal ratio, but it has slightly smaller caliper bores than yours, which require a smaller master cyl. I tried 15/16", 7/8", 13/16", liked the 13/16" the best.

Back to your problem. I think I'd try two sizes smaller since you are not even locking the brakes now.

There is an early 70's Ford master cyl that I tried, the stroke is good, better than the Malibu MC which has a limited stroke at aprox 1", - you may bottom the master cyl before the pedal hits the floor.

If you know the day and aprox time you bought the master cyl, the store may be able to find their copy of the reciept.

I'll post the part numbers later, I'm at work and don't have them here.
David

Thanks Dave, that would be helpful.