Choosing the right master cylinder
 

I've got the Wilwood disc brake conversion kit, part number 140-2285, on my 68 camaro and right now I'm running a wilwood 1" bore tandom master cylinder and the brakes just aren't performing like they should. I was told I need a smaller bore master cylinder and I just dont know weather I need a 7/8" bore or a 3/4" bore? Any help would be a huge help, thanks alot.

Do you have a power brake booster? Do you have drums in the back? are you running a adjustable prop valve? If you are running manual brakes with drum brakes in the rear then I would say go to a smaller bore size because it requires less leg effort to get more pressure however, you give up volume of fluid moved. This is an example of why you need to be more specific on what your set up has. It really depends on your whole system.

sorry, ive got stock drums in the back still, no power booster and i do have an adjustable proportioning valve for the rear

Yep - smaller MC bore = less pedal effort required
 

Bolt this 7/8" version in place of your 1" 260-8555 model and live happy:

http://store.summitracing.com/partde...0&autoview=sku

Ok thanks alot for the help, its appreciated

Hi need soem tech help as wel . car hase 13 inch ssbc force 10 in the frond and 12 inch single piston in the back engine thuse not diliver enoughf vacume for these brakes i whant to change over to hydra boost system i do have a DSE remote power stearing pump en resevroir. please adive what i need.

Your car looks like it is a 1st gen Firebird from looking at the attached images - correct? If so, our system # 3021 / 3023 or 3013 / 3014 will be a plug n play. What you should do for accuracy is to double check that your existing master cylinder is the later design without the deep MC pushrod hole as I supsect (as it looks like an aftermarket vacuum booster / MC combo, which is usually the short MC rod design) . Go ahead and unbolt the MC from the vac booster (while leaving the brake lines connected to the MC), then pull the MC out of the brake booster just far enough to see which MC rod design you are running. It is either going to be a short rod that does not stick out of the booster much, and a shallow little dimple in the MC piston - OR - it will have a long rod sticking out of the booster about an inch and a half and you would be able to stick a pencil into the back side of the MC about an inch and a half.

Here is a side by side comparison, with the early design / long MC rod style MC on the left, and the later design / short MC rod style on the right:

http://hydratechbraking.com/products...vs-shallow.jpg

Our standard production PS linesets are setup to accomodate your existing mini pump arrangement, so have no worries about this.

Paul its a first gen firebird alright. the master cilinder came with the compleat kit from SSBC..