[1950Mercury]

Today I ordered the shims to raise motor 3/16" from Aimes. I notice my 11" brake booster is very close to my valve covers. I'm thinking going to a 9" booster. This is a 66 GTO front disc dual master cyl. Does anyone have a part number for what works best? And the best vendor where to purchase.

[Barrier Blue]

I ordered mine from Summit Racing Equipment. It is Right Stuff Detailing Brake Booster part number RSD-RPB9121. They are in stock right now, and cost $143.95. I swapped it a couple weeks ago, and now have a full inch of clearance between it and the stock valve cover. It was an easy swap, and the only modification I had to make was shortening the push rod extension to match the length from my old aftermarket booster. The mounting brackets, depth of the unit , and bolt holes matched up fine.

[1950Mercury]

Thanks
Barrier Blue. After measuring mine it is a 9" already. My valve covers are aftermarket apparently. I am going to need probably a 8" if they make one or a 7". I wish the car didn't have power brakes but the car had them when I bought it and the holes are already there in the firewall.

[b-man]

It’s easy to just swap in a manual master and delete the booster. You just end up using the upper two studs on the firewall and the lower two don’t interfere with anything. Just put nuts and lock washers on the two lower studs to secure the pedal assembly.

Did exactly that on my ‘64 Le Mans convertible that was originally equipped with power brakes.

I’m swapping to a 1970 Firebird manual disc brake master cylinder with a 1” bore. Was actually using a 1-1/8” bore unit and it worked fine but since that one began leaking due to advanced age I’m swapping it for the 1” bore master to reduce pedal effort a bit.

I’m right now waiting for the 1” bore master to arrive on special order.

[Goatracer1]

You do NOT want an 8 inch or smaller booster. They are for very light cars like street rods.

[1950Mercury]

Looks like either I eliminate the power brakes or look for a set of chrome valve covers.

[b-man]

Installed the new 1” bore master sourced from my local NAPA store, part number M2163.

Was a bit surprised that they didn’t sell me a remanufactured unit and didn’t want my old one as a core, it’s new and manufactured in China like many mechanical replacement parts still available for old cars nowadays.

Works very well, the previous 1-1/8” master worked fine actually but this one works better and rightfully so because GM sized it for manual front disc brake cars. Pedal feel is a little softer and the increase in pedal travel is minimal.

[1950Mercury]

It's the same with brake shoes and water pumps. 20 years ago it was an exchange basis. Now everything is new Chinese no exchange.

[grivera]

What valve covers are you currently using and what rocker arms?

[1950Mercury]

I am not sure what they are but they are aftermarket and resemble the TransDapt tall. I picked up a set of the old Cal Custom aluminum ones the other day. They are shorter. Stock rockers and nuts on 670 heads.

[grivera]

Originally Posted by b-man

Installed the new 1” bore master sourced from my local NAPA store, part number M2163.

Was a bit surprised that they didn’t sell me a remanufactured unit and didn’t want my old one as a core, it’s new and manufactured in China like many mechanical replacement parts still available for old cars nowadays.

Works very well, the previous 1-1/8” master worked fine actually but this one works better and rightfully so because GM sized it for manual front disc brake cars. Pedal feel is a little softer and the increase in pedal travel is minimal.

What measurement did you use for the pushrod into the MC bore?

[76TA462]

Not sure if this is a fix, but may depend on how tall your valve covers are. When I changed to a taller valve train my brake boost would touch the valve cover when the engine tilted under throttle. No big deal and did not cause any problems, but bothered me so I changed to finned Indian style covers with thick gaskets because they get shorter at the ends, enough to create the clearance I needed. Might not be the case for you. Attached is a pic of the cover (not needed now due to other chages since).

[1950Mercury]

I put a set of early Cal Custom on and gained a good 3/4" or more. Stock valve train.