80ECLT said:
It had aluminum master. I have two piston front blazer calipers. Rear is single piston elderado calipers
How does your stock master cylinder work with your disc/disc conversion and your power brake booster?
I am guessing that there is some pedal travel before the brakes actually start to work? I had this issue when I upgraded my dad's 1980 El Camino brakes to the 2.75" big bore metric calipers. I think it may have more to do with the master cylinder being 31 years old and a little worn out.
Your stock 1980 El Camino master cylinder is a 24mm design which is pretty close to a 1" diameter master cylinder that came on the twin piston caliper blazers. There is only .055 inch between the two diameter. This difference is alot, but I think the power brake booster can compensate for the difference.
1980 g-body seems to be the only year to have a strait bore aluminum master cylinders (My dad had one on his 1980 El Camino). 1978 and 1979 had cast iron master cylinders and 1981 to 1988 had step bore aluminum master cylinders.
I have been down this road many times. There is no real good aluminum master cylinders for our cars. The aftermarket aluminum ones are not designed for our angled firewalls. The rebuilt and new 1978 to 1980 strait bore master cylinders are cast iron. The rebuilt step bore master cylinders from 1981 to 1988 are aluminum, but they have to many inherent problems to retro fit to your car plus the new ones are cast iron and really heavy.
Your original master cylinder is aluminum, is close to the 1" bore of the Blazer at 24mm, and is designed for a g-body angled firewall. I would rebuild your 1980 El Camino aluminum master cylinder first to see if the performance is better. It may be 30 years old, and a rebuild can not hurt.
