73 Master Cylinder w Power Brakes Gasket Question

[Roger C.]

Reviewing archive post indicate 730392 gasket & 9787620 retainer are no longer available from GM or other vendors. One of the post indicate the purpose of the gasket was to keep contamination out of the Vacuum booster and was not absolutely necessary for operation. Please refer to attached AIM page items# 6 & 7). Has anyone simply cut a gasket similiar to non power brakes (3790853 item# 4 on same attached Aim page) or should one just mount the master cylinder direct to booster with hope water and other contamiates does not enter between the master cylinder and booster. Thank you for your input.

[Joe L.]

Re: 73 Master Cylinder w Power Brakes Gasket Question

Reviewing archive post indicate 730392 gasket & 9787620 retainer are no longer available from GM or other vendors. One of the post indicate the purpose of the gasket was to keep contamination out of the Vacuum booster and was not absolutely necessary for operation. Please refer to attached AIM page items# 6 & 7). Has anyone simply cut a gasket similiar to non power brakes (3790853 item# 4 on same attached Aim page) or should one just mount the master cylinder direct to booster with hope water and other contamiates does not enter between the master cylinder and booster. Thank you for your input.

Roger------


The GM #3790853 is installed between the master cylinder and the firewall for non power brake applications. It will not work between the master cylinder and the booster. Even if you could use one, there's no reason to go to the bother of cutting one. This gasket is available from Dr. Rebuild and others.

The gasket between the master cylinder and the booster was a special gasket made of rubber. If I recall correctly, it also had an integral metal "frame".

[John H.]

Re: 73 Master Cylinder w Power Brakes Gasket Question

or should one just mount the master cylinder direct to booster with hope water and other contamiates does not enter between the master cylinder and booster.

Roger -

That's a molded rubber vacuum seal between the back of the master cylinder and the front face of the booster; you don't want to leave it out or substitute something that won't seal that joint.