Help with Brakes

[Shelbywh89]

Help with Brakes Problems.

I have a 78 Grand prix with Blazer Brakes upfront and 1985 Monte Carlo Calipers in the rear on a Quick Performance 9”.

I can’t get more then 50% Pedal with the brakes. I have a stock Disc Disc Prop Valve from Summit racing.

The master cylinder is stock. I believe that might be the problem. I’ve had it at two brake shops with no luck. One shop said the quick performance rear braided brake lines might be to big.

Everything is new, new stainless steel hard lines up to the rear and new booster.

Can you hook up the Wilwood prop in the OE location or would I need to redo the hardlines.

Or is it just using the stock master is limiting it.

Thank you for any help.

 

[Streetbu]

Rear caliper pistons are way too large.... Thats part of your problem

 

[spidereyes455]

The stock master cyl isn't helping either. The piston is to small to move enough fluid without ecsessive pedal travel.

 

[Shelbywh89]

Rear caliper pistons are way too large.... Thats part of your problem

🤔 If thats the case how are people putting C5 and Camaro calipers on four corners..😕Im not sure my options for switching them out since the whole rear is set up for disc

 

[Shelbywh89]

The stock master cyl isn't helping either. The piston is to small to move enough fluid without ecsessive pedal travel.

I think the master cyl is one of bigger problems with it...Hopefully switching that will solve the problem..

 

[spidereyes455]

When I put blazer discs at all 4 corners on my GP I originally used a 84 Eldorado master and still wasnt quite satisfied with how the pedal felt so I used an 81 trans am 4 wheel disc master since it had a larger bore and piston than even the Eldorado master, the lines were in the correct place and it's aluminum with a plastic resivore so it looks just like a stock G master cyl.

 

[Streetbu]

🤔 If thats the case how are people putting C5 and Camaro calipers on four corners..😕Im not sure my options for switching them out since the whole rear is set up for disc

Because they aren't using front calipers on the rear of a vehicle. Piston size on rear calipers are ALWAYS, MUCH smaller than the pistons on the front calipers of the same vehicle.

 

[MC96]

^ metric calipers on the rear of vehicles is super common.

That being said there are different caliper bore sizes for metric calipers available other than stock.

 

[Streetbu]

For dirt cars and that still doesn't make it right....

 

[MC96]

For dirt cars and that still doesn't make it right....

They make metric caliper brackets kits for just about every rear end out there. On as many hot rods as they are on dirt cars